Molecular And Cellular Biology[JOURNAL]
Sun
200 papers
Receptor Recycling by Retromer.
Carosi JM, Denton D, Kumar S … +1 more , Sargeant TJ
Mol Cell Biol · 2023 · PMID 37350516 · Full text
The highly conserved retromer complex controls the fate of hundreds of receptors that pass through the endolysosomal system and is a central regulatory node for diverse metabolic programs. More than 20 years ago, retrome...
The highly conserved retromer complex controls the fate of hundreds of receptors that pass through the endolysosomal system and is a central regulatory node for diverse metabolic programs. More than 20 years ago, retromer was discovered as an essential regulator of endosome-to-Golgi transport in yeast; since then, significant progress has been made to characterize how metazoan retromer components assemble to enable its engagement with endosomal membranes, where it sorts cargo receptors from endosomes to the -Golgi network or plasma membrane through recognition of sorting motifs in their cytoplasmic tails. In this review, we examine retromer regulation by exploring its assembled structure with an emphasis on how a range of adaptor proteins shape the process of receptor trafficking. Specifically, we focus on how retromer is recruited to endosomes, selects cargoes, and generates tubulovesicular carriers that deliver cargoes to target membranes. We also examine how cells adapt to distinct metabolic states by coordinating retromer expression and function. We contrast similarities and differences between retromer and its related complexes: retriever and commander/CCC, as well as their interplay in receptor trafficking. We elucidate how loss of retromer regulation is central to the pathology of various neurogenerative and metabolic diseases, as well as microbial infections, and highlight both opportunities and cautions for therapeutics that target retromer. Finally, with a focus on understanding the mechanisms that govern retromer regulation, we outline new directions for the field moving forward.
The "LINC" between Δ40p53-miRNA Axis in the Regulation of Cellular Homeostasis.
Pal A, Ghosh PK, Das S
Mol Cell Biol · 2023 · PMID 37283188 · Full text
Previous research has shown that Δ40p53, the translational isoform of p53, can inhibit cell growth independently of p53 by regulating microRNAs. Here, we explored the role of Δ40p53 in regulating the long noncoding RNA-m...
Previous research has shown that Δ40p53, the translational isoform of p53, can inhibit cell growth independently of p53 by regulating microRNAs. Here, we explored the role of Δ40p53 in regulating the long noncoding RNA-micro-RNA-cellular process axis, specifically focusing on . Interestingly, levels were predominantly affected by the overexpression/stress-mediated induction and knockdown of Δ40p53 rather than p53 levels. Additional assays revealed that Δ40p53 transactivates transcriptionally and could also regulate its stability. RNA immunoprecipitation experiments revealed that sequesters several putative microRNA targets, which could further titrate several mRNA targets involved in different cellular processes. To understand the downstream effects of this regulation, we ectopically overexpressed and knocked down in HCT116 p53-/- (harboring only Δ40p53) cells, which affected their proliferation, cell viability, and expression of epithelial markers. Our results provide essential insights into the pivotal role of Δ40p53 in regulating the novel RNA-microRNA-mRNA axis independent of FL-p53 and in maintaining cellular homeostasis.
Distinct Interaction Modes for the Eukaryotic RNA Polymerase Alpha-like Subunits.
Belkevich AE, Pascual HG, Fakhouri AM … +2 more , Ball DG, Knutson BA
Mol Cell Biol · 2023 · PMID 37222571 · Full text
Eukaryotic DNA-dependent RNA polymerases (Pols I-III) encode two distinct alpha-like heterodimers where one is shared between Pols I and III, and the other is unique to Pol II. Human alpha-like subunit mutations are asso...
Eukaryotic DNA-dependent RNA polymerases (Pols I-III) encode two distinct alpha-like heterodimers where one is shared between Pols I and III, and the other is unique to Pol II. Human alpha-like subunit mutations are associated with several diseases including Treacher Collins Syndrome (TCS), 4H leukodystrophy, and primary ovarian sufficiency. Yeast is commonly used to model human disease mutations, yet it remains unclear whether the alpha-like subunit interactions are functionally similar between yeast and human homologs. To examine this, we mutated several regions of the yeast and human small alpha-like subunits and used biochemical and genetic assays to establish the regions and residues required for heterodimerization with their corresponding large alpha-like subunits. Here we show that different regions of the small alpha-like subunits serve differential roles in heterodimerization, in a polymerase- and species-specific manner. We found that the small human alpha-like subunits are more sensitive to mutations, including a "humanized" yeast that we used to characterize the molecular consequence of the TCS-causingPOLR1D G52E mutation. These findings help explain why some alpha subunit associated disease mutations have little to no effect when made in their yeast orthologs and offer a better yeast model to assess the molecular basis of POLR1D associated disease mutations.
Dematin Regulates Calcium Mobilization, Thrombosis, and Early Akt Activation in Platelets.
Fritz DI, Ding Y, Merrill-Skoloff G … +3 more , Flaumenhaft R, Hanada T, Chishti AH
Mol Cell Biol · 2023 · PMID 37216480 · Full text
The complex intrinsic and extrinsic pathways contributing to platelet activation profoundly impact hemostasis and thrombosis. Detailed cellular mechanisms that regulate calcium mobilization, Akt activation, and integrin...
The complex intrinsic and extrinsic pathways contributing to platelet activation profoundly impact hemostasis and thrombosis. Detailed cellular mechanisms that regulate calcium mobilization, Akt activation, and integrin signaling in platelets remain incompletely understood. Dematin is a broadly expressed actin binding and bundling cytoskeletal adaptor protein regulated by phosphorylation via cAMP-dependent protein kinase. Here, we report the development of a conditional mouse model specifically lacking dematin in platelets. Using the new mouse model termed PDKO, we provide direct evidence that dematin is a major regulator of calcium mobilization, and its genetic deletion inhibits the early phase of Akt activation in response to collagen and thrombin agonists in platelets. The aberrant platelet shape change, clot retraction, and in vivo thrombosis observed in PDKO mice will enable future characterization of dematin-mediated integrin activation mechanisms in thrombogenic as well as nonvascular pathologies.
Phosphorylation of the Myogenic Factor Myocyte Enhancer Factor-2 Impacts Myogenesis In Vivo.
Vishal K, Barajas Alonso E, DeAguero AA … +3 more , Waters JA, Chechenova MB, Cripps RM
Mol Cell Biol · 2023 · PMID 37184381 · Full text
Activity of the myogenic regulatory protein myocyte enhancer factor-2 (MEF2) is modulated by post-translational modification. We investigated the in vivo phosphorylation of MEF2, and identified serine 98 (S98) as a phos...
Activity of the myogenic regulatory protein myocyte enhancer factor-2 (MEF2) is modulated by post-translational modification. We investigated the in vivo phosphorylation of MEF2, and identified serine 98 (S98) as a phosphorylated residue. Phospho-mimetic (S98E) and phospho-null (S98A) isoforms of MEF2 did not differ from wild-type in their activity in vitro, so we used CRISPR/Cas9 to generate an S98A allele of the endogenous gene. In mutant larvae we observed phenotypes characteristic of reduced MEF2 function, including reduced body wall muscle size and reduced expression of myofibrillar protein genes; conversely, homozygotes showed enhanced MEF2 function through muscle differentiation within the adult myoblasts associated with the wing imaginal disc. In adults, homozygotes were viable with normal mobility, yet showed patterning defects in muscles that were enhanced when the allele was combined with a null allele. Overall our data indicate that blocking MEF2 S98 phosphorylation in myoblasts enhances its myogenic capability, whereas blocking S98 phosphorylation in differentiating muscles attenuates MEF2 function. Our studies are among the first to assess the functional significance of MEF2 phosphorylation sites in the intact animal, and suggest that the same modification can have profoundly different effects upon MEF2 function depending upon the developmental context.
Transcription-Driven Translocation of Cohesive and Non-Cohesive Cohesin In Vivo.
Borrie MS, Kraycer PM, Gartenberg MR
Mol Cell Biol · 2023 · PMID 37178128 · Full text
Cohesin is a central architectural element of chromosomes that regulates numerous DNA-based events. The complex holds sister chromatids together until anaphase onset and organizes individual chromosomal DNAs into loops a...
Cohesin is a central architectural element of chromosomes that regulates numerous DNA-based events. The complex holds sister chromatids together until anaphase onset and organizes individual chromosomal DNAs into loops and self-associating domains. Purified cohesin diffuses along DNA in an ATP-independent manner but can be propelled by transcribing RNA polymerase. In conjunction with a cofactor, the complex also extrudes DNA loops in an ATP-dependent manner. In this study we examine transcription-driven translocation of cohesin under various conditions in yeast. To this end, obstacles of increasing size were tethered to DNA to act as roadblocks to complexes mobilized by an inducible gene. The obstacles were built from a GFP-lacI core fused to one or more mCherries. A chimera with four mCherries blocked cohesin passage in late G1. During M phase, the threshold barrier depended on the state of cohesion: non-cohesive complexes were also blocked by four mCherries whereas cohesive complexes were blocked by as few as three mCherries. Furthermore cohesive complexes that were stalled at obstacles, in turn, blocked the passage of non-cohesive complexes. That synthetic barriers capture mobilized cohesin demonstrates that transcription-driven complexes translocate processively in vivo. Together, this study reveals unexplored limitations to cohesin movement on chromosomes.
EPRS1 Controls the TGF- Signaling Pathway via Interaction with TβRI in Hepatic Stellate Cell.
Yoon I, Song JA, Suh JH … +7 more , Kim S, Son J, Kim JH, Jang SY, Hwang KY, Kim MH, Kim S
Mol Cell Biol · 2023 · PMID 37154023 · Full text
Glutamyl-prolyl-tRNA synthetase 1 (EPRS1) is known to associated with fibrosis through its catalytic activity to produce prolyl-tRNA. Although its catalytic inhibitor halofuginone (HF) has been known to inhibit the TGF-β...
Glutamyl-prolyl-tRNA synthetase 1 (EPRS1) is known to associated with fibrosis through its catalytic activity to produce prolyl-tRNA. Although its catalytic inhibitor halofuginone (HF) has been known to inhibit the TGF-β pathway as well as to reduce prolyl-tRNA production for the control of fibrosis, the underlying mechanism how EPRS1 regulates the TGF-β pathway was not fully understood. Here, we show a noncatalytic function of EPRS1 in controlling the TGF-β pathway and hepatic stellate cell activation via its interaction with TGF-β receptor I (TβRI). Upon stimulation with TGF-β, EPRS1 is phosphorylated by TGF-β-activated kinase 1 (TAK1), leading to its dissociation from the multi-tRNA synthetase complex and subsequent binding with TβRI. This interaction increases the association of TβRI with SMAD2/3 while decreases that of TβRI with SMAD7. Accordingly, EPRS1 stabilizes TβRI by preventing the ubiquitin-mediated degradation of TβRI. HF disrupts the interaction between EPRS1 and TβRI, and reduces TβRI protein levels, leading to inhibition of the TGF-β pathway. In conclusion, this work suggests the novel function of EPRS1 involved in the development of fibrosis by regulating the TGF-β pathway and the antifibrotic effects of HF by controlling both of EPRS1 functions.
A CDK-Dependent Phosphorylation of a Novel Domain of Rif1 Regulates its Function during Telomere Damage and Other Types of Stress.
Robertson CM, Xue Y, Chowdhury S … +1 more , Maringele L
Mol Cell Biol · 2023 · PMID 37140180 · Full text
Rif1 mediates telomere length, DNA replication, and DNA damage responses in budding yeast. Previous work identified several posttranslational modifications of Rif1, however none of these was shown to mediate the molecula...
Rif1 mediates telomere length, DNA replication, and DNA damage responses in budding yeast. Previous work identified several posttranslational modifications of Rif1, however none of these was shown to mediate the molecular or cellular responses to DNA damage, including telomere damage. We searched for such modifications using immunoblotting methods and the and models of telomere damage. We found that Rif1 is phosphorylated during telomere damage, and that serines 57 and 110 within a novel phospho-gate domain (PGD) of Rif1 are important for this modification, in cells. The phosphorylation of Rif1 appeared to inhibit its accumulation on damaged chromosomes and the proliferation of cells with telomere damage. Moreover, we found that checkpoint kinases were upstream of this Rif1 phosphorylation and that the Cdk1 activity was essential for maintaining it. Apart from telomere damage, S57 and S110 were essential for Rif1 phosphorylation during the treatment of cells with genotoxic agents or during mitotic stress. We propose a speculative "Pliers" model to explain the role of the PGD phosphorylation during telomere and other types of damage.
Chaperone-Dependent Degradation of Cdc42 Promotes Cell Polarity and Shields the Protein from Aggregation.
González B, Aldea M, Cullen PJ
Mol Cell Biol · 2023 · PMID 37114947 · Full text
Rho GTPases are global regulators of cell polarity and signaling. By exploring the turnover regulation of the yeast Rho GTPase Cdc42p, we identified new regulatory features surrounding the stability of the protein. We sp...
Rho GTPases are global regulators of cell polarity and signaling. By exploring the turnover regulation of the yeast Rho GTPase Cdc42p, we identified new regulatory features surrounding the stability of the protein. We specifically show that Cdc42p is degraded at 37 °C by chaperones through lysine residues located in the C-terminus of the protein. Cdc42p turnover at 37 °C occurred by the 26S proteasome in an ESCRT-dependent manner in the lysosome/vacuole. By analyzing versions of Cdc42p that were defective for turnover, we show that turnover at 37 °C promoted cell polarity but was defective for sensitivity to mating pheromone, presumably mediated through a Cdc42p-dependent MAP kinase pathway. We also identified one residue (K16) in the P-loop of the protein that was critical for Cdc42p stability. Accumulation of Cdc42p in some contexts led to the formation of protein aggregates, which were enriched in aging mother cells and cells undergoing proteostatic stress. Our study uncovers new aspects of protein turnover regulation of a Rho-type GTPase that may extend to other systems. Moreover, residues identified here that mediate Cdc42p turnover correlate with several human diseases, which may suggest that turnover regulation of Cdc42p is important to aspects of human health.
Hsp70 Binding to the N-terminal Domain of Hsp104 Regulates [] Curing by Hsp104 Overexpression.
Zhao X, Stanford K, Ahearn J … +2 more , Masison DC, Greene LE
Mol Cell Biol · 2023 · PMID 37099734 · Full text
Hsp104 propagates the yeast prion [], the infectious form of Sup35, by severing the prion seeds, but when Hsp104 is overexpressed, it cures [] in a process that is not yet understood but may be caused by trimming, which...
Hsp104 propagates the yeast prion [], the infectious form of Sup35, by severing the prion seeds, but when Hsp104 is overexpressed, it cures [] in a process that is not yet understood but may be caused by trimming, which removes monomers from the ends of the amyloid fibers. This curing was shown to depend on both the N-terminal domain of Hsp104 and the expression level of various members of the Hsp70 family, which raises the question as to whether these effects of Hsp70 are due to it binding to the Hsp70 binding site that was identified in the N-terminal domain of Hsp104, a site not involved in prion propagation. Investigating this question, we now find, first, that mutating this site prevents both the curing of [] by Hsp104 overexpression and the trimming activity of Hsp104. Second, we find that depending on the specific member of the Hsp70 family binding to the N-terminal domain of Hsp104, both trimming and the curing caused by Hsp104 overexpression are either increased or decreased in parallel. Therefore, the binding of Hsp70 to the N-terminal domain of Hsp104 regulates both the rate of [] trimming by Hsp104 and the rate of [] curing by Hsp104 overexpression.
DNA Damage-Induced, S-Phase Specific Phosphorylation of Orc6 is Critical for the Maintenance of Genome Stability.
Lin YC, Liu D, Chakraborty A … +9 more , Macias V, Brister E, Sonalkar J, Shen L, Mitra J, Ha T, Kajdacsy-Balla A, Prasanth KV, Prasanth SG
Mol Cell Biol · 2023 · PMID 37096556 · Full text
The smallest subunit of the human Origin Recognition Complex, hOrc6, is required for DNA replication progression and plays an important role in mismatch repair (MMR) during S-phase. However, the molecular details of how...
The smallest subunit of the human Origin Recognition Complex, hOrc6, is required for DNA replication progression and plays an important role in mismatch repair (MMR) during S-phase. However, the molecular details of how hOrc6 regulates DNA replication and DNA damage response remain to be elucidated. Orc6 levels are elevated upon specific types of genotoxic stress, and it is phosphorylated at Thr229, predominantly during S-phase, in response to oxidative stress. Many repair pathways, including MMR, mediate oxidative DNA damage repair. Defects in MMR are linked to Lynch syndrome, predisposing patients to many cancers, including colorectal cancer. Orc6 levels are known to be elevated in colorectal cancers. Interestingly, tumor cells show reduced hOrc6-Thr229 phosphorylation compared to adjacent normal mucosa. Further, elevated expression of wild-type and the phospho-dead forms of Orc6 results in increased tumorigenicity, implying that in the absence of this "checkpoint" signal, cells proliferate unabated. Based on these results, we propose that DNA-damage-induced hOrc6-pThr229 phosphorylation during S-phase facilitates ATR signaling in the S-phase, halts fork progression, and enables assembly of repair factors to mediate efficient repair to prevent tumorigenesis. Our study provides novel insights into how hOrc6 regulates genome stability.
Hypoxia-Inducible Factor-2alpha Affects the MEK/ERK Signaling Pathway via Primary Cilia in Connection with the Intraflagellar Transport Protein 88 Homolog.
Leu T, Denda J, Wrobeln A … +1 more , Fandrey J
Mol Cell Biol · 2023 · PMID 37074220 · Full text
The ability of cells to communicate with their surrounding is a prerequisite for essential processes such as proliferation, apoptosis, migration, and differentiation. To this purpose, primary cilia serve as antennae-like...
The ability of cells to communicate with their surrounding is a prerequisite for essential processes such as proliferation, apoptosis, migration, and differentiation. To this purpose, primary cilia serve as antennae-like structures on the surface of most mammalian cell types. Cilia allow signaling via hedgehog, Wnt or TGF-beta pathways. Their length, in part controlled by the activity of intraflagellar transport (IFT), is a parameter for adequate function of primary cilia. Here we show, in murine neuronal cells, that intraflagellar transport protein 88 homolog (IFT88) directly interacts with the hypoxia-inducible factor-2α (HIF-2α), hitherto known as an oxygen-regulated transcription factor. Furthermore, HIF-2α accumulates in the ciliary axoneme and promotes ciliary elongation under hypoxia. Loss of HIF-2α affected ciliary signaling in neuronal cells by decreasing transcription of and . Targets of the MEK/ERK signaling pathway, such as and , were significantly decreased. Our results suggest that HIF-2α influences ciliary signaling by interacting with IFT88 under hypoxic conditions. This implies an unexpected and far more extensive function of HIF-2α than described before.
Recruitment of RBM6 to DNA Double-Strand Breaks Fosters Homologous Recombination Repair.
Awwad SW, Darawshe MM, Machour FE … +2 more , Arman I, Ayoub N
Mol Cell Biol · 2023 · PMID 36941773 · Full text
DNA double-strand breaks (DSBs) are highly toxic lesions that threaten genome integrity and cell survival. To avoid harmful repercussions of DSBs, a wide variety of DNA repair factors are recruited to execute DSB repair....
DNA double-strand breaks (DSBs) are highly toxic lesions that threaten genome integrity and cell survival. To avoid harmful repercussions of DSBs, a wide variety of DNA repair factors are recruited to execute DSB repair. Previously, we demonstrated that RBM6 splicing factor facilitates homologous recombination (HR) of DSB by regulating alternative splicing-coupled nonstop-decay of the HR protein APBB1/Fe65. Here, we describe a splicing-independent function of RBM6 in promoting HR repair of DSBs. We show that RBM6 is recruited to DSB sites and PARP1 activity indirectly regulates RBM6 recruitment to DNA breakage sites. Deletion mapping analysis revealed a region containing five glycine residues within the G-patch domain that regulates RBM6 accumulation at DNA damage sites. We further ascertain that RBM6 interacts with Rad51, and this interaction is attenuated in RBM6 mutant lacking the G-patch domain (RBM6). Consequently, RBM6 cells exhibit reduced levels of Rad51 foci after ionizing radiation. In addition, while RBM6 deletion mutant lacking the G-patch domain has no detectable effect on the expression levels of its splicing targets Fe65 and Eya2, it fails to restore the integrity of HR. Altogether, our results suggest that RBM6 recruitment to DSB promotes HR repair, irrespective of its splicing activity.HIGHLIGHTSPARP1 activity indirectly regulates RBM6 recruitment to DNA damage sites.Five glycine residues within the G-patch domain of RBM6 are critical for its recruitment to DNA damage sites, but dispensable for its splicing activity.RBM6 G-patch domain fosters its interaction with Rad51 and promotes Rad51 foci formation following irradiation.RBM6 recruitment to DSB sites underpins HR repair.
Methyltransferase Inhibition Enables Tgf Driven Induction of and in Cancer Cells.
Liu YT, Romero C, Xiao X … +5 more , Guo L, Zhou X, Applebaum MA, Xu L, Skapek SX
Mol Cell Biol · 2023 · PMID 36941772 · Full text
deletion or silencing is common across human cancer, reinforcing the general importance of bypassing its tumor suppression in cancer formation or progression. In rhabdomyosarcoma (RMS) and neuroblastoma, two common child...
deletion or silencing is common across human cancer, reinforcing the general importance of bypassing its tumor suppression in cancer formation or progression. In rhabdomyosarcoma (RMS) and neuroblastoma, two common childhood cancers, the three transcripts are independently expressed to varying degrees, but one, is uniformly silenced. Although TGFβ induces certain transcripts in HeLa cells, it was unable to do so in five tested RMS lines unless the cells were pretreated with a broadly acting methyltransferase inhibitor, DZNep, or one targeting EZH2. induction by TGFβ correlated with de novo appearance of three H3K27Ac peaks within a 20 kb element ∼150 kb proximal to . Deleting that segment prevented their induction by TGFβ but not a basal increase driven by methyltransferase inhibition alone. Expression of two transcripts was enhanced by dCas9/CRISPR activation targeting either the relevant promoter or the 20 kb elements, and this "precise" manipulation diminished RMS cell propagation in vitro. Our findings show crosstalk between methyltransferase inhibition and TGFβ-dependent activation of a remote enhancer to reverse silencing. Though focused on here, such crosstalk may apply to other TGFβ-responsive genes and perhaps govern this signaling protein's complex effects promoting or blocking cancer.
Eukaryotic Clathrin Adapter Protein and Mediator of Cholesterol Homeostasis, PICALM, Affects Trafficking to the Chlamydial Inclusion.
Jorgenson LM, Knight L, Widner RE … +1 more , Rucks EA
Mol Cell Biol · 2023 Feb · PMID 36779337 · Full text
The obligate intracellular pathogen has unique metabolic requirements as it proceeds through its biphasic developmental cycle from within the inclusion within the host cell. In our previous study, we identified a host p...
The obligate intracellular pathogen has unique metabolic requirements as it proceeds through its biphasic developmental cycle from within the inclusion within the host cell. In our previous study, we identified a host protein, PICALM, which localizes to the chlamydial inclusion. PICALM functions in many host pathways including the recycling of receptors, specific SNARE proteins, and molecules like transferrin, and maintaining cholesterol homeostasis. Hence, we hypothesized that PICALM functions to maintain the cholesterol content and to moderate trafficking from the endosomal recycling pathway to the inclusion, which controls chlamydial access to this pathway. In uninfected cells, siRNA knockdown of PICALM resulted in increased cholesterol within the Golgi and transferrin receptor (TfR) positive vesicles (recycling endosomes). PICALM knockdown in cells infected with resulted in increased levels of Golgi-derived lipid and protein, TfR, transferrin, and Rab11-FIP1 localized to inclusions and a decrease of Golgi fragmentation at and Rab11 trafficking to the inclusion. Interestingly, chlamydial infection alone also increases cholesterol in TfR and Rab11-associated vesicles, and PICALM knockdown reverses this effect. Our data suggest that PICALM functions to balance or limit chlamydial access to multiple subcellular trafficking pathways to maintain the health of the host cell during chlamydial infection.
Incomplete Elongation of Ultra-long-chain Polyunsaturated Acyl-CoAs by the Fatty Acid Elongase ELOVL4 in Spinocerebellar Ataxia Type 34.
Tamura Y, Sassa T, Nishizawa T … +1 more , Kihara A
Mol Cell Biol · 2023 Feb · PMID 36748939 · Full text
Spinocerebellar ataxias (SCAs) are autosomal dominant diseases characterized by cerebellar atrophy and ataxia. The SCA subtype SCA34 is caused by specific mutations in the gene , which encodes a fatty acid (FA) elongase...
Spinocerebellar ataxias (SCAs) are autosomal dominant diseases characterized by cerebellar atrophy and ataxia. The SCA subtype SCA34 is caused by specific mutations in the gene , which encodes a fatty acid (FA) elongase that synthesizes ultra-long-chain (ULC; ≥C26) FAs. However, the pathogenesis and molecular mechanism that confers dominant inheritance remains unknown. Here, a cell-based assay demonstrated that each of the five known SCA34 mutants produced shorter ULC polyunsaturated FA-containing phosphatidylcholines (ULC-PCs) than wild-type protein, in the following order of severity: Q180P and T233M > W246G > I171T and L168F. Next, we generated knock-in mouse embryonic stem cells that contained heterozygous Q180P, heterozygous W246G, or homozygous W246G mutations. Neuronal differentiation-dependent production of ULC-PCs was reduced in heterozygous Q180P and homozygous W246G cells relative to control cells, and we observed shortening of the FA moiety in all mutant cells. This FA shortening was consistent with our prediction that amino acid residues substituted by SCA34 mutations are located in the transmembrane helices that interact with the ω-end region of the FA moiety of the substrate acyl-CoA. Hence, reduced levels and shortening of ULC-PCs in neurons may cause SCA34, and incomplete elongation of ULC polyunsaturated acyl-CoAs by mutated may induce dominant inheritance.
Exosome-transmitted circ Modulates Ovarian Cancer Metastasis via miR-378/ST5 Axis.
Chen X, Ren X, E J … +2 more , Zhou Y, Bian R
Mol Cell Biol · 2023 Jan · PMID 36720469 · Full text
Cancer-associated fibroblasts (CAFs)-derived exosomes have emerged as a key driver of ovarian cancer (OVCA) tumor progression. The mechanisms behind the specific circular RNA (circRNA) activity encapsulated by CAF-genera...
Cancer-associated fibroblasts (CAFs)-derived exosomes have emerged as a key driver of ovarian cancer (OVCA) tumor progression. The mechanisms behind the specific circular RNA (circRNA) activity encapsulated by CAF-generated exosomes (CAF-exo) requires to be elucidated. Herein, this study selected specific circRNA (hsa_circ) molecules and aimed to clarify novel function of CAF-derived exosomal circ on growth, and metastasis of OVCA cells. In this study, we clarified that the exosomes of CAFs originating from human ovarian cancer hindered tumor cell proliferation, metastasis and EMT in vitro. Interestingly, CAFs directly transferred exosomes into OVCA cells to enrich intracellular circ levels. Biologically, activation of exosomal circ blocked cell proliferation, metastasis and EMT. Mechanistically, enhanced circ activated the miR-378/ST5 axis and directly inhibited the malignant evolution of tumor cells. Furthermore, rescue experiments evidenced that circ and ST5 were two essential participants in OVCA, concretely manifested in the co-culture of OVCA cells with exosomes that reversed the effects of intracellular circ and ST5 depletion. Finally, we observed that CAF-exo treatment hindered tumor growth and increased the size and number of metastatic nodules in mice. Our study revealed a previously unknown regulatory pathway whereby CAFs-derived exosomes delivered circ and inhibited the malignant progression of OVCA by circ/miR-378/ST5 axis.
Transcriptional Regulation of by Aryl Hydrocarbon Receptor: Effect on Math1 Progenitor Cells in Mouse Small Intestine.
Yagishita Y, Joshi T, Kensler TW … +1 more , Wakabayashi N
Mol Cell Biol · 2023 Jan · PMID 36720468 · Full text
The physiological roles of aryl hydrocarbon receptor (AhR) in the small intestine have been revealed as immunomodulatory and barrier functions. However, its contributions to cell fate regulation are incompletely understo...
The physiological roles of aryl hydrocarbon receptor (AhR) in the small intestine have been revealed as immunomodulatory and barrier functions. However, its contributions to cell fate regulation are incompletely understood. The Notch-activated signaling cascade is a central component of intestinal cell fate determinations. The lateral inhibitory mechanism governed by Notch directs cell fates toward distinct cell lineages (i.e., absorptive and secretory cell lineages) through its downstream effector, mouse atonal homolog 1 (MATH1). An investigation employing cell lines and intestinal crypt cells revealed that AhR regulates expression in a xenobiotic response element (XRE)-dependent manner. The AhR- axis was further addressed using intestinal organoids, where AhR- and HES1- axes appeared to coexist within the underlying transcriptional machinery. When the HES1- axis was pharmacologically suppressed, β-naphthoflavone-mediated AhR activation increased the number of goblet and Math1 progenitor cells in the organoids. The same pharmacological dissection of the AhR- axis was applied in vivo, demonstrating an enhanced number of Math1 progenitor cells in the small intestine following AhR activation. We report here that AhR- is a direct transcriptional axis with effects on Math1 progenitor cells in the small intestine, highlighting a novel molecular basis for fine-tuning Notch-mediated cell fate regulation.
Claspin is Required for Growth Recovery from Serum Starvation through Regulating the PI3K-PDK1-mTOR Pathway in Mammalian Cells.
Yang CC, Masai H
Mol Cell Biol · 2023 Jan · PMID 36720467 · Full text
Claspin plays multiple important roles in regulation of DNA replication as a mediator for the cellular response to replication stress, an integral replication fork factor that facilitates replication fork progression and...
Claspin plays multiple important roles in regulation of DNA replication as a mediator for the cellular response to replication stress, an integral replication fork factor that facilitates replication fork progression and a factor that promotes initiation by recruiting Cdc7 kinase. Here, we report a novel role of Claspin in growth recovery from serum starvation, which requires the activation of PI3 kinase (PI3K)-PDK1-Akt-mTOR pathways. In the absence of Claspin, cells do not proceed into S phase and eventually die partially in a ROS- and p53-dependent manner. Claspin directly interacts with PI3K and mTOR, and is required for activation of PI3K-PDK1-mTOR and for that of mTOR downstream factors, p70S6K and 4EBP1, but not for p38 MAPK cascade during the recovery from serum starvation. PDK1 physically interacts with Claspin, notably with CKBD, in a manner dependent on phosphorylation of the latter protein, and is required for interaction of mTOR with Claspin. Thus, Claspin plays a novel role as a key regulator for nutrition-induced proliferation/survival signaling by activating the mTOR pathway. The results also suggest a possibility that Claspin may serve as a common mediator that receives signals from different PI3K-related kinases and transmit them to specific downstream kinases.
Sumoylation is Largely Dispensable for Normal Growth but Facilitates Heat Tolerance in Yeast.
Moallem M, Akhter A, Burke GL … +5 more , Babu J, Bergey BG, McNeil JB, Baig MS, Rosonina E
Mol Cell Biol · 2023 Jan · PMID 36720466 · Full text
Numerous proteins are sumoylated in normally growing yeast and SUMO conjugation levels rise upon exposure to several stress conditions. We observe high levels of sumoylation also during early exponential growth and when...
Numerous proteins are sumoylated in normally growing yeast and SUMO conjugation levels rise upon exposure to several stress conditions. We observe high levels of sumoylation also during early exponential growth and when nutrient-rich medium is used. However, we find that reduced sumoylation (∼75% less than normal) is remarkably well-tolerated, with no apparent growth defects under nonstress conditions or under osmotic, oxidative, or ethanol stresses. In contrast, strains with reduced activity of Ubc9, the sole SUMO conjugase, are temperature-sensitive, implicating sumoylation in the heat stress response, specifically. Aligned with this, a mild heat shock triggers increased sumoylation which requires functional levels of Ubc9, but likely also depends on decreased desumoylation, since heat shock reduces protein levels of Ulp1, the major SUMO protease. Furthermore, we find that a mutant strain with only ∼5% of normal sumoylation levels shows a modest growth defect, has abnormal genomic distribution of RNA polymerase II (RNAPII), and displays a greatly expanded redistribution of RNAPII after heat shock. Together, our data implies that SUMO conjugations are largely dispensable under normal conditions, but a threshold level of Ubc9 activity is needed to maintain transcriptional control and to modulate the redistribution of RNAPII and promote survival when temperatures rise.
About
- Frequency
- Sun
- Papers found
- 200
- RSS feed
- Subscribe