Biochim. Biophys. Acta [JOURNAL]
Sun
200 papers
The role of cholesterol and sphingolipids in the dopamine D receptor and G protein distribution in the plasma membrane.
Mystek P, Dutka P, Tworzydło M … +2 more , Dziedzicka-Wasylewska M, Polit A
Biochim Biophys Acta · 2016 Nov · PMID 27570114 · Publisher ↗
G proteins are peripheral membrane proteins which interact with the inner side of the plasma membrane and form part of the signalling cascade activated by G protein-coupled receptors (GPCRs). Since many signalling protei...
G proteins are peripheral membrane proteins which interact with the inner side of the plasma membrane and form part of the signalling cascade activated by G protein-coupled receptors (GPCRs). Since many signalling proteins do not appear to be homogeneously distributed on the cell surface, they associate in particular membrane regions containing specific lipids. Therefore, protein-lipid interactions play a pivotal role in cell signalling. Our previous results showed that although Gαs and Gαi prefer different types of membrane domains they are both co-localized with the D receptor. In the present report we characterize the role of cholesterol and sphingolipids in the membrane localization of Gαs, Gαi and their heterotrimers, as well as the D receptor. We measured the lateral diffusion and membrane localization of investigated proteins using fluorescence recovery after photobleaching (FRAP) microscopy and fluorescence resonance energy transfer (FRET) detected by lifetime imaging microscopy (FLIM). The treatment with either methyl-β-cyclodextrin or Fumonisin B led to the disruption of cholesterol-sphingolipids containing domains and changed the diffusion of Gαi and the D receptor but not of Gαs. Our results imply a sequestration of Gαs into cholesterol-independent solid-like membrane domains. Gαi prefers cholesterol-dependent lipid rafts so it does not bind to those domains and its diffusion is reduced. In turn, the D receptor exists in several different membrane localizations, depending on the receptor's conformation. We conclude that the inactive G protein heterotrimers are localized in the low-density membrane phase, from where they displace upon dissociation into the membrane-anchor- and subclass-specific lipid domain.
Ceramide and polyunsaturated phospholipids are strongly reduced in human hepatocellular carcinoma.
Krautbauer S, Meier EM, Rein-Fischboeck L … +6 more , Pohl R, Weiss TS, Sigruener A, Aslanidis C, Liebisch G, Buechler C
Biochim Biophys Acta · 2016 Nov · PMID 27570113 · Publisher ↗
Lipid composition affects membrane function, cell proliferation and cell death and is changed in cancer tissues. Hepatocellular carcinoma (HCC) is an aggressive cancer and this study aimed at a comprehensive characteriza...
Lipid composition affects membrane function, cell proliferation and cell death and is changed in cancer tissues. Hepatocellular carcinoma (HCC) is an aggressive cancer and this study aimed at a comprehensive characterization of hepatic and serum lipids in human HCC. Cholesteryl ester were higher in tumorous tissues (TT) compared to adjacent non-tumorous tissues (NT). Free cholesterol exerting cytotoxic effects was not changed. Phosphatidylethanolamine, -serine (PS) and -inositol but not phosphatidylcholine (PC) and lysophosphatidylcholine (LPC) were reduced in HCC tissues. Saturated species mostly increased and polyunsaturated species were diminished in all of these phospholipids. Ceramide (Cer) was markedly reduced in HCC tissues and higher levels of sphingomyelin suggest impaired sphingomyelinase activity as one of the underlying mechanisms. Importantly, ceramide in NT increased in HCC stage T3. Ceramide released from hepatocytes attracts immune cells and a positive association of the macrophage specific receptor CD163 with NT ceramide was identified. HCC associated lipid changes did not differ in patients suffering from type 2 diabetes. Protein levels of p53 were induced in TT and negatively correlated with Cer d18:1/16:0 and PS 36:1. Of the lipid species changed in HCC tissues only TT Cer d18:1/16:0, Cer d18:1/24:1, PC 38:6 and LPC 22:6 correlated with the respective serum levels. Our study demonstrates a considerably altered hepatic lipidome in HCC tissues. Ceramide was markedly reduced in HCC tissues, and therefore, raising ceramide levels specifically in the tumor represents a reasonable therapeutic approach for the treatment of this malignancy.
Atomic modelling and systematic mutagenesis identify residues in multiple drug binding sites that are essential for drug resistance in the major Candida transporter Cdr1.
Nim S, Lobato LG, Moreno A … +4 more , Chaptal V, Rawal MK, Falson P, Prasad R
Biochim Biophys Acta · 2016 Nov · PMID 27569110 · Publisher ↗
The ABC (ATP-Binding Cassette) transporter Cdr1 (Candida drug resistance 1) protein (Cdr1p) of Candida albicans, shows promiscuity towards the substrate it exports and plays a major role in antifungal resistance. It has...
The ABC (ATP-Binding Cassette) transporter Cdr1 (Candida drug resistance 1) protein (Cdr1p) of Candida albicans, shows promiscuity towards the substrate it exports and plays a major role in antifungal resistance. It has two transmembrane domains (TMDs) comprising of six transmembrane helices (TMH) that envisage and confer the substrate specificity and two nucleotide binding domains (NBDs), interconnected by extracellular loops (ECLs) and intracellular loops (ICLs) Cdr1p. This study explores the diverse substrate specificity spectrum to get a deeper insight into the structural and functional features of Cdr1p. By screening with the variety of compounds towards an in-house TMH 252 mutant library of Cdr1p, we establish new substrates of Cdr1p. The localization of substrate-susceptible mutants in an ABCG5/G8 homology model highlights the common and specific binding pockets inside the membrane domain, where rhodamines and tetrazoliums mainly engage the N-moiety of Cdr1p, binding between TMH 2, 11 and surrounded by TMH 1, 5. Whereas, tin chlorides involve both N and C moieties located at the interface of TMH 2, 11, 1 and 5. Further, screening of the in house TMH mutant library of Cdr1p displays the TMH12 interaction with tetrazolium chloride, trimethyltin chloride and a Ca ionophore, A23187. In silico localization reveals a binding site at the TMH 12, 9 and 10 interface, which is widely exposed to the lipid interface. Together, for the first time, our study shows the molecular localization of Cdr1p substrates-binding sites and demonstrates the participation of TMH12 in a peripheral drug binding site.
An impaired metabolism of nucleotides underpins a novel mechanism of cardiac remodeling leading to Huntington's disease related cardiomyopathy.
Toczek M, Zielonka D, Zukowska P … +5 more , Marcinkowski JT, Slominska E, Isalan M, Smolenski RT, Mielcarek M
Biochim Biophys Acta · 2016 Nov · PMID 27568644 · Publisher ↗
Huntington's disease (HD) is mainly thought of as a neurological disease, but multiple epidemiological studies have demonstrated a number of cardiovascular events leading to heart failure in HD patients. Our recent studi...
Huntington's disease (HD) is mainly thought of as a neurological disease, but multiple epidemiological studies have demonstrated a number of cardiovascular events leading to heart failure in HD patients. Our recent studies showed an increased risk of heart contractile dysfunction and dilated cardiomyopathy in HD pre-clinical models. This could potentially involve metabolic remodeling, that is a typical feature of the failing heart, with reduced activities of high energy phosphate generating pathways. In this study, we sought to identify metabolic abnormalities leading to HD-related cardiomyopathy in pre-clinical and clinical settings. We found that HD mouse models developed a profound deterioration in cardiac energy equilibrium, despite AMP-activated protein kinase hyperphosphorylation. This was accompanied by a reduced glucose usage and a significant deregulation of genes involved in de novo purine biosynthesis, in conversion of adenine nucleotides, and in adenosine metabolism. Consequently, we observed increased levels of nucleotide catabolites such as inosine, hypoxanthine, xanthine and uric acid, in murine and human HD serum. These effects may be caused locally by mutant HTT, via gain or loss of function effects, or distally by a lack of trophic signals from central nerve stimulation. Either may lead to energy equilibrium imbalances in cardiac cells, with activation of nucleotide catabolism plus an inhibition of re-synthesis. Our study suggests that future therapies should target cardiac mitochondrial dysfunction to ameliorate energetic dysfunction. Importantly, we describe the first set of biomarkers related to heart and skeletal muscle dysfunction in both pre-clinical and clinical HD settings.
Interleukin-17A mediates cardiomyocyte apoptosis through Stat3-iNOS pathway.
Su SA, Yang D, Zhu W … +5 more , Cai Z, Zhang N, Zhao L, Wang JA, Xiang M
Biochim Biophys Acta · 2016 Nov · PMID 27566322 · Publisher ↗
Interleukin-17A, a pro-inflammatory cytokine, has a direct proapoptotic effect on cardiomyocytes. However, the specific mechanism has not been clarified. In the present study, an in-vitro model of cardiomyocyte apoptosis...
Interleukin-17A, a pro-inflammatory cytokine, has a direct proapoptotic effect on cardiomyocytes. However, the specific mechanism has not been clarified. In the present study, an in-vitro model of cardiomyocyte apoptosis induced by IL-17A stimulation was employed and the roles of iNOS and Stat3 involved were investigated. Our data showed that the neonatal mouse cardiomyocytes express IL-17 receptors: IL-17RA and IL-17RC, but did not express IL-17A. Exogenous IL-17A significantly induces iNOS expression and hence the cardiomyocyte apoptosis. Moreover, IL-17A-induced cardiomyocyte apoptosis can be achieved directly via iNOS activation. We further showed that exogenous IL-17A simultaneously triggers Stat3 activation, which in turn inhibits IL-17A-induced iNOS expression in cardiomyocytes. And both ChIP and dual-luciferase results confirmed that Stat3 directly inhibits transcriptional activities of iNOS via binding to its specific promoter region. Consistent with these data, silencing of Stat3 in fact can aggravate IL-17A-triggered cardiomyocyte apoptosis. Finally, using an in vivo myocardial ischemia/reperfusion injury model, we verified that Stat3 inhibition increased iNOS expression and exacerbated cardiomyocyte apoptosis. Thus, our data strongly support the notion that Stat3 plays a compensatory anti-apoptotic role in IL-17A/iNOS-mediated cardiomyocyte apoptosis via inhibiting iNOS transcription, providing a novel molecular mechanism of apoptosis regulation and complicated interactions between IL-17A/iNOS and IL-17A/Stat3 signalings.
Dysregulation of a potassium channel, THIK-1, targeted by caspase-8 accelerates cell shrinkage.
Sakamaki K, Ishii TM, Sakata T … +18 more , Takemoto K, Takagi C, Takeuchi A, Morishita R, Takahashi H, Nozawa A, Shinoda H, Chiba K, Sugimoto H, Saito A, Tamate S, Satou Y, Jung SK, Matsuoka S, Koyamada K, Sawasaki T, Nagai T, Ueno N
Biochim Biophys Acta · 2016 Nov · PMID 27566292 · Publisher ↗
Activation of caspases is crucial for the execution of apoptosis. Although the caspase cascade associated with activation of the initiator caspase-8 (CASP8) has been investigated in molecular and biochemical detail, the...
Activation of caspases is crucial for the execution of apoptosis. Although the caspase cascade associated with activation of the initiator caspase-8 (CASP8) has been investigated in molecular and biochemical detail, the physiological role of CASP8 is not fully understood. Here, we identified a two-pore domain potassium channel, tandem-pore domain halothane-inhibited K channel 1 (THIK-1), as a novel CASP8 substrate. The intracellular region of THIK-1 was cleaved by CASP8 in apoptotic cells. Overexpression of THIK-1, but not its mutant lacking the CASP8-target sequence in the intracellular portion, accelerated cell shrinkage in response to apoptotic stimuli. In contrast, knockdown of endogenous THIK-1 by RNA interference resulted in delayed shrinkage and potassium efflux. Furthermore, a truncated THIK-1 mutant lacking the intracellular region, which mimics the form cleaved by CASP8, led to a decrease of cell volume of cultured cells without apoptotic stimulation and excessively promoted irregular development of Xenopus embryos. Taken together, these results indicate that THIK-1 is involved in the acceleration of cell shrinkage. Thus, we have demonstrated a novel physiological role of CASP8: creating a cascade that advances the cell to the next stage in the apoptotic process.
Ph(-) myeloproliferative neoplasm red blood cells display deregulation of IQGAP1-Rho GTPase signaling depending on CALR/JAK2 status.
Socoro-Yuste N, Dagher MC, Gonzalez De Peredo A … +6 more , Mondet J, Zaccaria A, Roux Dalvai F, Plo I, Cahn JY, Mossuz P
Biochim Biophys Acta · 2016 Nov · PMID 27566291 · Publisher ↗
Besides genetic abnormalities in MPN patients, several studies have reported alterations in protein expression that could contribute towards the clinical phenotype. However, little is known about protein modifications in...
Besides genetic abnormalities in MPN patients, several studies have reported alterations in protein expression that could contribute towards the clinical phenotype. However, little is known about protein modifications in Ph MPN erythrocytes. In this context, we used a quantitative mass spectrometry proteomics approach to study the MPN erythrocyte proteome. LC-MS/MS (LTQ Orbitrap) analysis led to the identification of 51 and 86 overexpressed proteins in Polycythemia Vera and Essential Thrombocythemia respectively, compared with controls. Functional comparison using pathway analysis software showed that the Rho GTPase family signaling pathways were deregulated in MPN patients. In particular, IQGAP1 was significantly overexpressed in MPNs compared with controls. Additionally, Western-blot analysis not only confirmed IQGAP1 overexpression, but also showed that IQGAP1 levels depended on the patient's genotype. Moreover, we found that in JAK2V617F patients IQGAP1 could bind RhoA, Rac1 and Cdc42 and consequently recruit activated GTP-Rac1 and the cytoskeleton motility protein PAK1. In CALR(+) patients, IQGAP1 was not overexpressed but immunoprecipitated with RhoGDI. In JAK2V617F transduced Ba/F3 cells we confirmed JAK2 inhibitor-sensitive overexpression of IQGAP1/PAK1. Altogether, our data demonstrated alterations of IQGAP1/Rho GTPase signaling in MPN erythrocytes dependent on JAK2/CALR status, reinforcing the hypothesis that modifications in erythrocyte signaling pathways participate in Ph MPN pathogenesis.
c-Abl links APP-BACE1 interaction promoting APP amyloidogenic processing in Niemann-Pick type C disease.
Yáñez MJ, Belbin O, Estrada LD … +6 more , Leal N, Contreras PS, Lleó A, Burgos PV, Zanlungo S, Alvarez AR
Biochim Biophys Acta · 2016 Nov · PMID 27565738 · Publisher ↗
BACKGROUND: Niemann-Pick type C (NPC) disease is characterized by lysosomal accumulation of cholesterol. Interestingly, NPC patients' brains also show increased levels of amyloid-β (Aβ) peptide, a key protein in Alzheime...
BACKGROUND: Niemann-Pick type C (NPC) disease is characterized by lysosomal accumulation of cholesterol. Interestingly, NPC patients' brains also show increased levels of amyloid-β (Aβ) peptide, a key protein in Alzheimer's disease pathogenesis. We previously reported that the c-Abl tyrosine kinase is active in NPC neurons and in AD animal models and that Imatinib, a specific c-Abl inhibitor, decreased the amyloid burden in brains of the AD mouse model. Active c-Abl was shown to interact with the APP cytosolic domain, but the relevance of this interaction to APP processing has yet to be defined. RESULTS: In this work we show that c-Abl inhibition reduces APP amyloidogenic cleavage in NPC cells overexpressing APP. Indeed, we found that levels of the Aβ oligomers and the carboxy-terminal fragment βCTF were decreased when the cells were treated with Imatinib and upon shRNA-mediated c-Abl knockdown. Moreover, Imatinib decreased APP amyloidogenic processing in the brain of an NPC mouse model. In addition, we found decreased levels of βCTF in neuronal cultures from c-Abl null mice. We demonstrate that c-Abl directly interacts with APP, that c-Abl inhibition prevents this interaction, and that Tyr682 in the APP cytoplasmic tail is essential for this interaction. More importantly, we found that c-Abl inhibition by Imatinib significantly inhibits the interaction between APP and BACE1. CONCLUSION: We conclude that c-Abl activity facilitates the APP-BACE1 interaction, thereby promoting amyloidogenic processing of APP. Thus, inhibition of c-Abl could be a pharmacological target for preventing the injurious effects of increased Aβ levels in NPC disease.
Negative feedback circuitry between MIR143HG and RBM24 in Hirschsprung disease.
Du C, Shen Z, Zang R … +7 more , Xie H, Li H, Chen P, Hang B, Xu X, Tang W, Xia Y
Biochim Biophys Acta · 2016 Nov · PMID 27565737 · Publisher ↗
Hirschsprung disease (HSCR) is a genetic disorder of neural crest development. It is also believed that epigenetic changes plays a role in the progression of this disease. Here we show that the MIR143 host gene (MIR143HG...
Hirschsprung disease (HSCR) is a genetic disorder of neural crest development. It is also believed that epigenetic changes plays a role in the progression of this disease. Here we show that the MIR143 host gene (MIR143HG), the precursor of miR-143 and miR-145, decreased cell proliferation and migration and forms a negative feedback loop with RBM24 in HSCR. As RBM24 mRNA is a target of miR-143, upregulation of RBM24 upon an increase in the level of MIR143HG could be attributed to sequestration of miR-143 by MIR143HG (sponge effect). The RBM24 protein was shown to bind to MIR143HG, and subsequently, accelerated its degradation by destabilizing its transcript and facilitating its interaction with Ago2, thus forming a negative feedback between MIR143HG and RBM24. In addition, experiments using siRNA against DROSHA indicated that RBM24 could promote the biogenesis of miR-143. This feedback loop we describe here represents a novel mode of autoregulation, with implications in HSCR pathogenesis.
Important roles for membrane lipids in haloarchaeal bioenergetics.
Kellermann MY, Yoshinaga MY, Valentine RC … +2 more , Wörmer L, Valentine DL
Biochim Biophys Acta · 2016 Nov · PMID 27565574 · Publisher ↗
Recent advances in lipidomic analysis in combination with various physiological experiments set the stage for deciphering the structure-function of haloarchaeal membrane lipids. Here we focused primarily on changes in li...
Recent advances in lipidomic analysis in combination with various physiological experiments set the stage for deciphering the structure-function of haloarchaeal membrane lipids. Here we focused primarily on changes in lipid composition of Haloferax volcanii, but also performed a comparative analysis with four other haloarchaeal species (Halobacterium salinarum, Halorubrum lacusprofundi, Halorubrum sodomense and Haloplanus natans) all representing distinctive cell morphologies and behaviors (i.e., rod shape vs. pleomorphic behavior). Common to all five haloarchaea, our data reveal an extraordinary high level of menaquinone, reaching up to 72% of the total lipids. This ubiquity suggests that menaquinones may function beyond their ordinary role as electron and proton transporter, acting simultaneously as ion permeability barriers and as powerful shield against oxidative stress. In addition, we aimed at understanding the role of cations interacting with the characteristic negatively charged surface of haloarchaeal membranes. We propose for instance that by bridging the negative charges of adjacent anionic phospholipids, Mg acts as surrogate for cardiolipin, a molecule that is known to control curvature stress of membranes. This study further provides a bioenergetic perspective as to how haloarchaea evolved following oxygenation of Earth's atmosphere. The success of the aerobic lifestyle of haloarchaea includes multiple membrane-based strategies that successfully balance the need for a robust bilayer structure with the need for high rates of electron transport - collectively representing the molecular basis to inhabit hypersaline water bodies around the planet.
Distinct mechanisms underlying cholesterol protection against alcohol-induced BK channel inhibition and resulting vasoconstriction.
Bisen S, Seleverstov O, Belani J … +3 more , Rychnovsky S, Dopico AM, Bukiya AN
Biochim Biophys Acta · 2016 Nov · PMID 27565113 · Full text
Alcohol (ethanol) at concentrations reached in blood following moderate to heavy drinking (30-80mM) reduces cerebral artery diameter via inhibition of voltage- and calcium-gated potassium channels of large conductance (B...
Alcohol (ethanol) at concentrations reached in blood following moderate to heavy drinking (30-80mM) reduces cerebral artery diameter via inhibition of voltage- and calcium-gated potassium channels of large conductance (BK) in cerebral artery smooth muscle. These channels consist of channel-forming α and regulatory β1 subunits. A high-cholesterol diet protects against ethanol-induced constriction via accumulation of cholesterol within the vasculature. The molecular mechanisms of this protection remain unknown. In the present work, we demonstrate that in vitro cholesterol enrichment of rat middle cerebral arteries significantly increased cholesterol within arterial tissues and blunted constriction by 50mM of ethanol. Ethanol-induced BK channel inhibition in inside-out patches excised from freshly isolated cerebral artery myocytes was also abolished by cholesterol enrichment. Enrichment of arteries with enantiomeric cholesterol (ent-cholesterol) also blunted BK channel inhibition and cerebral artery constriction in response to ethanol. The similar protection of cholesterol and ent-cholesterol against ethanol action indicates that this protection does not require protein site(s) that specifically sense natural cholesterol. Cholesterol-driven protection against ethanol-induced BK channel inhibition and vasoconstriction was replicated in myocytes and middle cerebral arteries of C57BL/6 mice. BK β1 subunits are known to regulate vascular diameter and its modification by ethanol. However, blunting of an ethanol effect by in vitro cholesterol enrichment was observed in arteries and myocyte membrane patches from BK β1 (KCNMB1) knockout mice. Thus, BK β1 subunits are not needed for cholesterol protection against ethanol effect on BK channel function and cerebral artery diameter.
Decellularized matrices as in vitro models of extracellular matrix in tumor tissues at different malignant levels: Mechanism of 5-fluorouracil resistance in colorectal tumor cells.
Hoshiba T, Tanaka M
Biochim Biophys Acta · 2016 Nov · PMID 27558478 · Publisher ↗
Chemoresistance is a major barrier for tumor chemotherapy. It is well-known that chemoresistance increases with tumor progression. Chemoresistance is altered by both genetic mutations and the alteration of extracellular...
Chemoresistance is a major barrier for tumor chemotherapy. It is well-known that chemoresistance increases with tumor progression. Chemoresistance is altered by both genetic mutations and the alteration of extracellular microenvironment. Particularly, the extracellular matrix (ECM) is remodeled during tumor progression. Therefore, ECM remodeling is expected to cause the acquisition of chemoresistance in highly malignant tumor tissue. Here, we prepared cultured cell-derived decellularized matrices that mimic native ECM in tumor tissues at different stages of malignancy, and 5-fluorouracil (5-FU) resistance was compared among these matrices. 5-FU resistance of colorectal tumor cells increased on the matrices derived from highly malignant tumor HT-29 cells, although the resistance did not increase on the matrices derived from low malignant tumor SW480 cells and normal CCD-841-CoN cells. The resistance on HT-29 cell-derived matrices increased through the activation of Akt and the upregulation of ABCB1 and ABCC1 without cell growth promotion, suggesting that ECM remodeling plays important roles in the acquisition of chemoresistance during tumor progression. It is expected that our decellularized matrices, or "staged tumorigenesis-mimicking matrices", will become preferred cell culture substrates for in vitro analysis of comprehensive ECM roles in chemoresistance and the screening and pharmacokinetic analysis of anti-cancer drugs.
Reversible FMN dissociation from Escherichia coli respiratory complex I.
Holt PJ, Efremov RG, Nakamaru-Ogiso E … +1 more , Sazanov LA
Biochim Biophys Acta · 2016 Nov · PMID 27555334 · Publisher ↗
Respiratory complex I transfers electrons from NADH to quinone, utilizing the reaction energy to translocate protons across the membrane. It is a key enzyme of the respiratory chain of many prokaryotic and most eukaryoti...
Respiratory complex I transfers electrons from NADH to quinone, utilizing the reaction energy to translocate protons across the membrane. It is a key enzyme of the respiratory chain of many prokaryotic and most eukaryotic organisms. The reversible NADH oxidation reaction is facilitated in complex I by non-covalently bound flavin mononucleotide (FMN). Here we report that the catalytic activity of E. coli complex I with artificial electron acceptors potassium ferricyanide (FeCy) and hexaamineruthenium (HAR) is significantly inhibited in the enzyme pre-reduced by NADH. Further, we demonstrate that the inhibition is caused by reversible dissociation of FMN. The binding constant (K) for FMN increases from the femto- or picomolar range in oxidized complex I to the nanomolar range in the NADH reduced enzyme, with an FMN dissociation time constant of ~5s. The oxidation state of complex I, rather than that of FMN, proved critical to the dissociation. Such dissociation is not observed with the T. thermophilus enzyme and our analysis suggests that the difference may be due to the unusually high redox potential of Fe-S cluster N1a in E. coli. It is possible that the enzyme attenuates ROS production in vivo by releasing FMN under highly reducing conditions.
In utero exposure to gestational diabetes mellitus conditions TLR4 and TLR2 activated IL-1beta responses in spleen cells from rat offspring.
Li Q, Pereira TJ, Moyce BL … +4 more , Mahood TH, Doucette CA, Rempel J, Dolinsky VW
Biochim Biophys Acta · 2016 Nov · PMID 27555296 · Publisher ↗
Fetal exposure to gestational diabetes mellitus (GDM) is associated with a higher risk of youth-onset insulin resistance and type 2 diabetes. We have previously shown that the rat offspring of GDM dams are insulin resist...
Fetal exposure to gestational diabetes mellitus (GDM) is associated with a higher risk of youth-onset insulin resistance and type 2 diabetes. We have previously shown that the rat offspring of GDM dams are insulin resistant when compared to the offspring of lean dams. Since inflammation influences insulin sensitivity, we examined the impact of fetal exposure to GDM on inflammatory responses in the offspring. In rats, we compared inflammatory activity in newborn pups as well as 16week-old young-adult offspring from lean control dams with offspring from high fat and sucrose diet (HFS)-induced GDM dams. To determine whether there are additive effects of exposure to GDM and post-weaning diets, offspring of lean and GDM dams were fed either low fat or HFS diets until 16weeks of age. Plasma levels of interleukin(IL)-1β were elevated in the offspring of GDM dams. To determine whether this was related to immune reactivity, spleen cells from both the newborn and 16week-old offspring were isolated and reactivity to the toll-like receptor activators, pam3CSK4 and lipopolysaccharides were measured over a 72h timeframe. Spleen cells of GDM dams exhibited sustained stimulation of interleukin(IL)-1β and IL-10 production, whereas IL-1β and IL-10 synthesis diminished over time in spleen cells from the offspring of lean dams. Additive effects of GDM exposure and post-weaning HFS diet were not observed, suggesting the effects of GDM on cytokine production are independent of the post-weaning diet. Thus, we conclude that exposure to GDM in utero may condition the immune reactivity of spleen cells.
MiR-29a promotes cell proliferation and EMT in breast cancer by targeting ten eleven translocation 1.
Pei YF, Lei Y, Liu XQ
Biochim Biophys Acta · 2016 Nov · PMID 27555295 · Publisher ↗
Increasing evidence has shown that microRNAs played an important role in regulating carcinogenesis. However, the role of miR-29a in breast cancer is still unclear. Herein, we showed that miR-29a was significantly up-regu...
Increasing evidence has shown that microRNAs played an important role in regulating carcinogenesis. However, the role of miR-29a in breast cancer is still unclear. Herein, we showed that miR-29a was significantly up-regulated in breast cancer as compared with non-tumor tissues. Moreover, the up-regulation of miR-29a was significantly correlated with tumor metastasis and shorter overall survival in breast cancer patients. Knockdown of miR-29a in breast cancer cell lines inhibited cell proliferation and migration. Furthermore, data from bioinformatic analysis validated by dual-luciferase reporter gene assay showed that ten eleven translocation 1 (TET1) was a direct target of miR-29a, and over-expression of TET1 inhibited cell proliferation and migration which could be induced by the up-regulation of miR-29a. TET1 silencing promoted cell growth and migration in breast cancer. MiR-29a over-expression had the same effect. MiR-29a targets TET1, down regulates its expression and thus promotes EMT in breast cancer. Altogether, we demonstrate that miR-29a acts as a tumor activator by targeting TET1 and induces cell proliferation and EMT in breast cancer.
The ganglioside GM1 interacts with the serotonin receptor via the sphingolipid binding domain.
Prasanna X, Jafurulla M, Sengupta D … +1 more , Chattopadhyay A
Biochim Biophys Acta · 2016 Nov · PMID 27552916 · Publisher ↗
Glycosphingolipids are minor yet essential components of eukaryotic cell membranes and are involved in a variety of cellular processes. Although glycosphingolipids such as GM1 have been previously reported to influence t...
Glycosphingolipids are minor yet essential components of eukaryotic cell membranes and are involved in a variety of cellular processes. Although glycosphingolipids such as GM1 have been previously reported to influence the function of G protein-coupled receptors (GPCRs), the molecular mechanism remains elusive. In this paper, we have explored the interaction of GM1 with the serotonin receptor, an important neurotransmitter receptor that belongs to the GPCR family. To examine the molecular basis of the interaction of GM1 with the serotonin receptor, we performed a series of coarse-grain molecular dynamics simulations of the receptor embedded in membrane bilayers containing GM1. Our results show that GM1 interacts with the serotonin receptor predominantly at the extracellular loop 1 and specifically at the sphingolipid binding domain (SBD). The SBD motif consists of a characteristic combination of aromatic, basic and turn-inducing residues, and is evolutionarily conserved in case of the serotonin receptor. The interaction of the SBD site with GM1 appears to stabilize a 'flip-out' conformation in which W102 of the extracellular loop 1 flips out from the central lumen of the receptor toward the membrane. The population of the 'flip-out' conformation is increased in the presence of cholesterol. Our data strongly suggest that a direct interaction between GM1 and the SBD site of the serotonin receptor may occur in vivo. In view of the reported role of GM1 and the serotonin receptor in neurodegenerative diseases, GM1-receptor interaction assumes significance in the context of malfunctioning of neuronal GPCRs under such conditions.
Nucleosome assembly and disassembly activity of GRWD1, a novel Cdt1-binding protein that promotes pre-replication complex formation.
Aizawa M, Sugimoto N, Watanabe S … +2 more , Yoshida K, Fujita M
Biochim Biophys Acta · 2016 Nov · PMID 27552915 · Publisher ↗
GRWD1 was previously identified as a novel Cdt1-binding protein that possesses histone-binding and nucleosome assembly activities and promotes MCM loading, probably by maintaining chromatin openness at replication origin...
GRWD1 was previously identified as a novel Cdt1-binding protein that possesses histone-binding and nucleosome assembly activities and promotes MCM loading, probably by maintaining chromatin openness at replication origins. However, the molecular mechanisms underlying these activities remain unknown. We prepared reconstituted mononucleosomes from recombinant histones and a DNA fragment containing a nucleosome positioning sequence, and investigated the effects of GRWD1 on them. GRWD1 could disassemble these preformed mononucleosomes in vitro in an ATP-independent manner. Thus, our data suggest that GRWD1 facilitates removal of H2A-H2B dimers from nucleosomes, resulting in formation of hexasomes. The activity was compromised by deletion of the acidic domain, which is required for efficient histone binding. In contrast, nucleosome assembly activity of GRWD1 was not affected by deletion of the acidic domain. In HeLa cells, the acidic domain of GRWD1 was necessary to maintain chromatin openness and promote MCM loading at replication origins. Taken together, our results suggest that GRWD1 promotes chromatin fluidity by influencing nucleosome structures, e.g., by transient eviction of H2A-H2B, and thereby promotes efficient MCM loading at replication origins.
A-type lamin-dependent homo-oligomerization for pY19-Caveolin-2 to function as an insulin-response epigenetic regulator.
Kwon H, Lee J, Jeong K … +3 more , Jang D, Choi M, Pak Y
Biochim Biophys Acta · 2016 Nov · PMID 27552914 · Publisher ↗
Association of Caveolin-2 in the inner nuclear membrane specifically with A-type lamin is crucial for the maintenance of its Tyr-19 phosphorylation to promote insulin-response epigenetic activation at the nuclear periphe...
Association of Caveolin-2 in the inner nuclear membrane specifically with A-type lamin is crucial for the maintenance of its Tyr-19 phosphorylation to promote insulin-response epigenetic activation at the nuclear periphery. Here, we identify that pY19-Caveolin-2 in the inner nuclear membrane exists as homo-oligomeric forms and the A-type lamin is required for sustenance of its oligomeric status. Oligomerization-defective and hence pY19-dephosphorylated monomeric Caveolin-2 in the inner nuclear membrane is unable to carry out Caveolin-2-mediated epigenetic activation of Egr-1 and JunB genes and transactivation of Elk-1 and STAT3 in response to insulin. The homo-oligomeric pY19-Caveolin-2 localizes in and recruits epigenetic modifiers to the A-type lamin-enriched inner nuclear membrane microdomain for the epigenetic activation. Our data show that A-type lamin-dependent Caveolin-2 homo-oligomerization in the inner nuclear membrane microdomain is a precondition for pY19-Caveolin-2-mediated insulin-response epigenetic activation at the nuclear periphery.
Stearoyl-CoA desaturase-1 and adaptive stress signaling.
Koeberle A, Löser K, Thürmer M
Biochim Biophys Acta · 2016 Nov · PMID 27550503 · Publisher ↗
Stearoyl-CoA desaturase (SCD), the central enzyme in the biosynthesis of monounsaturated fatty acids, introduces a cis-Δ9 double bond into saturated fatty acids. SCD-1 has been proposed as promising target for the treatm...
Stearoyl-CoA desaturase (SCD), the central enzyme in the biosynthesis of monounsaturated fatty acids, introduces a cis-Δ9 double bond into saturated fatty acids. SCD-1 has been proposed as promising target for the treatment of cancer, skin disorders and metabolic diseases, and strong efforts have been made during the last decade to develop clinical drug candidates. While the regulation and biological implications of SCD-1 have been extensively reviewed, the molecular mechanisms through which SCD-1 mediates cellular responses remained a mystery. An important aspect seems to be that SCD-1 induces adaptive stress signaling that maintains cellular persistence and fosters survival and cellular functionality under distinct pathological conditions. Here, we will first provide an overview about the function, regulation, structure and mechanism of SCD-1 and then focus on mitogenic and stress-related signal transduction pathways orchestrated by SCD-1. Moreover, we will discuss molecular mechanisms and potential lipid factors that link SCD-1 activity with initial signal transduction.
The cytochrome b Zn binding amino acid residue histidine 291 is essential for ubihydroquinone oxidation at the Q site of bacterial cytochrome bc.
Francia F, Malferrari M, Lanciano P … +3 more , Steimle S, Daldal F, Venturoli G
Biochim Biophys Acta · 2016 Nov · PMID 27550309 · Full text
The ubiquinol:cytochrome (cyt) c oxidoreductase (or cyt bc) is an important membrane protein complex in photosynthetic and respiratory energy transduction. In bacteria such as Rhodobacter capsulatus it is constituted of...
The ubiquinol:cytochrome (cyt) c oxidoreductase (or cyt bc) is an important membrane protein complex in photosynthetic and respiratory energy transduction. In bacteria such as Rhodobacter capsulatus it is constituted of three subunits: the iron-sulfur protein, cyt b and cyt c, which form two catalytic domains, the Q (hydroquinone (QH) oxidation) and Q (quinone (Q) reduction) sites. At the Q site, the pathways of bifurcated electron transfers emanating from QH oxidation are known, but the associated proton release routes are not well defined. In energy transducing complexes, Zn binding amino acid residues often correlate with proton uptake or release pathways. Earlier, using combined EXAFS and structural studies, we identified Zn coordinating residues of mitochondrial and bacterial cyt bc. In this work, using the genetically tractable bacterial cyt bc, we substituted each of the proposed Zn binding residues with non-protonatable side chains. Among these mutants, only the His291Leu substitution destroyed almost completely the Q site catalysis without perturbing significantly the redox properties of the cofactors or the assembly of the complex. In this mutant, which is unable to support photosynthetic growth, the bifurcated electron transfer reactions that result from QH oxidation at the Q site, as well as the associated proton(s) release, were dramatically impaired. Based on these findings, on the putative role of His291 in liganding Zn, and on its solvent exposed and highly conserved position, we propose that His291 of cyt b is critical for proton release associated to QH oxidation at the Q site of cyt bc.
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