Zhang H, Wang X, Xi K
… +16 more, Shen Q, Xue J, Zhu Y, Zang SK, Yu T, Shen DD, Guo J, Chen LN, Ji SY, Qin J, Dong Y, Zhao M, Yang M, Wu H, Yang G, Zhang Y
Activation of the μ-opioid receptor (μOR) alleviates pain but also elicits adverse effects through diverse G proteins and β-arrestins. The structural details of μOR complexes with G and β-arrestins have not been determin...Activation of the μ-opioid receptor (μOR) alleviates pain but also elicits adverse effects through diverse G proteins and β-arrestins. The structural details of μOR complexes with G and β-arrestins have not been determined, impeding a comprehensive understanding of μOR signaling plasticity. Here, we present the cryo-EM structures of the μOR-G and μOR-βarr1 complexes, revealing selective conformational preferences of μOR when engaged with specific downstream signaling transducers. Integrated receptor pharmacology, including high-resolution structural analysis, cell signaling assays, and molecular dynamics simulations, demonstrated that transmembrane helix 1 (TM1) acts as an allosteric regulator of μOR signaling bias through differential stabilization of the G-, G-, and βarr1-bound states. Mechanistically, outward TM1 displacement confers structural flexibility that promotes G protein recruitment, whereas inward TM1 retraction facilitates βarr1 recruitment by stabilizing the intracellular binding pocket through coordinated interactions with TM2, TM7, and helix8. Structural comparisons between the G-, G-, and βarr1-bound complexes identified a TM1-fusion pocket with significant implications for downstream signaling regulation. Overall, we demonstrate that the conformational and thermodynamic heterogeneity of TM1 allosterically drives the downstream signaling specificity and plasticity of μOR, thereby expanding the understanding of μOR signal transduction mechanisms and providing new avenues for the rational design of analgesics.
The innate immune system adapts its behavior based on previous insults, mounting an enhanced response upon re-exposure. Hematopoietic progenitors in the bone marrow and peripheral innate immune cells can undergo epigenet...The innate immune system adapts its behavior based on previous insults, mounting an enhanced response upon re-exposure. Hematopoietic progenitors in the bone marrow and peripheral innate immune cells can undergo epigenetic and metabolic reprogramming, establishing an innate immune memory known as trained immunity. The concept of trained immunity recently gained relevance in our understanding of how innate immunity is regulated in various diseases. This review explores the role of trained immunity in infections, autoimmune disease, cardiovascular disease, cancer, and neurodegenerative disease. We discuss how trained immunity can provide heterologous protection against infections, as it has been induced for decades by the Bacillus Calmette Guérin vaccine, how it can help counteract immunosuppression, and how it can be inappropriately induced leading to chronic inflammation. By understanding how trained immunity is involved in processes leading to health and disease, novel therapeutic strategies can be developed.
Zhong L, Lin X, Cheng X
… +27 more, Wan S, Hua Y, Nan W, Hu B, Peng X, Zhou Z, Zhang Q, Yang H, Noé F, Yan Z, Jiang D, Zhang H, Liu F, Xiao C, Zhou Z, Mou Y, Yu H, Ma L, Huang C, Wong VKW, Chung SK, Shen B, Jiang ZH, Neher E, Zhu W, Zhang J, Hou P
The KCNQ1 + KCNE1 potassium channel complex produces the slow delayed rectifier current (I) critical for cardiac repolarization. Loss-of-function mutations in KCNQ1 and KCNE1 cause long QT syndrome (LQTS) types 1 and 5 (...The KCNQ1 + KCNE1 potassium channel complex produces the slow delayed rectifier current (I) critical for cardiac repolarization. Loss-of-function mutations in KCNQ1 and KCNE1 cause long QT syndrome (LQTS) types 1 and 5 (LQT1/LQT5), accounting for over one-third of clinical LQTS cases. Despite prior structural work on KCNQ1 and KCNQ1 + KCNE3, the structural basis of KCNQ1 + KCNE1 remains unresolved. Using cryo-electron microscopy and electrophysiology, we determined high-resolution (2.5-3.4 Å) structures of human KCNQ1, and KCNQ1 + KCNE1 in both closed and open states. KCNE1 occupies a pivotal position at the interface of three KCNQ1 subunits, inducing six helix-to-loop transitions in KCNQ1 transmembrane segments. Three of them occur at both ends of the S4-S5 linker, maintaining a loop conformation during I gating, while the other three, in S6 and helix A, undergo dynamic helix-loop transitions during I gating. These structural rearrangements: (1) stabilize the closed pore and the conformation of the intermediate state voltage-sensing domain, thereby determining channel gating, ion permeation, and single-channel conductance; (2) enable a dual-PIP2 modulation mechanism, where one PIP2 occupies the canonical site, while the second PIP2 bridges the S4-S5 linker, KCNE1, and the adjacent S6', stabilizing channel opening; (3) create a fenestration capable of binding compounds specific for KCNQ1 + KCNE1 (e.g., AC-1). Together, these findings reveal a previously unrecognized large-scale secondary structural transition during ion channel gating that fine-tunes I function and provides a foundation for developing targeted LQTS therapy.
Lineage plasticity, the ability of cells to transition to an alternative phenotype as a means for adaptation, is an increasingly recognized mechanism of tumor evolution and a driver of resistance to anticancer therapies....Lineage plasticity, the ability of cells to transition to an alternative phenotype as a means for adaptation, is an increasingly recognized mechanism of tumor evolution and a driver of resistance to anticancer therapies. The most extensively described clinical settings impacted by such molecular phenomena include neuroendocrine transformation in androgen receptor-dependent prostate adenocarcinoma, and adenocarcinoma-to-neuroendocrine and adenocarcinoma-to-squamous transdifferentiation in epidermal growth factor receptor-driven lung adenocarcinoma, affecting 10%-20% of patients treated with targeted therapy. Recent analyses of human tumor samples and in vivo models of histological transformation have led to insights into the biology of lineage plasticity, including biomarkers predictive of high risk of transformation. However, no clinically available therapies aimed to prevent or revert plasticity are currently available. In the present review, we will provide a biological and therapeutic overview of the current understanding of common and divergent molecular drivers of neuroendocrine and squamous transdifferentiation in tumors from different origins, including descriptive analysis of previously known and recently described molecular events associated with histological transformation, and propose evidence-based alternative models of transdifferentiation. A clear definition of the commonalities and differences of transforming tumors in different organs and to different histological fates will be important to translate molecular findings to the clinical setting.
MDA5 is a RIG-I-like receptor (RLR) that recognizes viral double-stranded RNA (dsRNA) to initiate the innate immune response. Its activation requires filament formation along the dsRNA, which triggers the oligomerization...MDA5 is a RIG-I-like receptor (RLR) that recognizes viral double-stranded RNA (dsRNA) to initiate the innate immune response. Its activation requires filament formation along the dsRNA, which triggers the oligomerization of N-terminal caspase activation and recruitment domains. The ATPase activity of MDA5 is critical for immune homeostasis, likely by regulating filament assembly. However, the molecular basis underlying this process remains poorly understood. Here, we show that MDA5 operates as an ATP-hydrolysis-driven motor that translocates along dsRNA in a one-dimensional (1D) manner. Multiple MDA5 motors can cooperatively load onto a single dsRNA, but their movements rarely synchronize, inhibiting spontaneous filament formation and activation. LGP2, a key regulator of MDA5 signaling, recognizes MDA5 motors and blocks their movement, thereby promoting filament assembly through a translocation-directed mechanism. This unique assembly strategy underscores the role of 1D motion in higher-order protein oligomerization and reveals a novel mechanism for maintaining immune homeostasis.
Tissue factor (TF) is a cell surface protein critical for normal hemostasis and pathological thrombosis. Necroptosis is a form of regulated necrosis associated with different diseases. Here, we reported the identificatio...Tissue factor (TF) is a cell surface protein critical for normal hemostasis and pathological thrombosis. Necroptosis is a form of regulated necrosis associated with different diseases. Here, we reported the identification of the first functional soluble tissue factor (sTF) in mediating blood coagulation, shed from the membrane full-length TF (flTF) by proteases, ADAMs, during necroptosis. By generating sTF-specific antibody and transgenic mice carrying knockin mutations at the ADAM cleavage site of TF (T211V212 mutated to E211E212), we demonstrated that this sTF is responsible for necroptosis-related thrombosis in inflammation and viral infection mouse models. Importantly, we showed that eliminating necroptosis or the cleavage of the flTF blocked the production of sTF and prevented thrombosis in mice. We also detected sTF in the plasma of human COVID-19 patients and showed that SARS-CoV-2 pseudovirus induced sTF production. Our findings demonstrated that the sTF plays a major role in thrombosis under necroptosis-related pathological conditions and provided a diagnostic marker and potential therapies for treating thrombosis without affecting hemostasis.
An optimal duration of inflammation protects against pathogens while a drawn-out inflammatory response is associated with chronic disease. Wang and colleagues propose the WSTF protein, whose autophagic degradation during...An optimal duration of inflammation protects against pathogens while a drawn-out inflammatory response is associated with chronic disease. Wang and colleagues propose the WSTF protein, whose autophagic degradation during prolonged inflammation results in a pro-inflammatory environment, as a target for augmentation to devise new treatments for chronic inflammatory diseases.
The pre-dimerization of endosome-localized RNA sensor Toll-like receptor 3 (TLR3) is required for its innate recognition, yet how TLR3 pre-dimers are formed and precisely primed for innate activation remains unclear. Her...The pre-dimerization of endosome-localized RNA sensor Toll-like receptor 3 (TLR3) is required for its innate recognition, yet how TLR3 pre-dimers are formed and precisely primed for innate activation remains unclear. Here, we demonstrate that endosome-localized self RNA Rmrp directly binds to TLR3 and induces TLR3 dimerization in the early endosome but does not interact with endosome-localized TLR7, TLR8, TLR9 or cytoplasmic RNA sensor RIG-I under homeostatic conditions. Cryo-EM structure of Rmrp-TLR3 complex reveals a novel lapped conformation of TLR3 dimer engaged by Rmrp, which is distinct from the activation mechanism by dsRNA and the specific structural feature at the 3'-end of Rmrp is critical for its functional interaction with TLR3. Furthermore, K42 residue of TLR3 is essential for binding to Rmrp and subsequent dimerization. Rmrp dissociates from TLR3 following endosomal acidification, generating a matured TLR3 dimer which is primed for innate recognition and activation. Myeloid-cell deficiency of Rmrp reduces TLR3 dimerization and attenuates TLR3-mediated antiviral responses against influenza A both in vitro and in vivo. These findings elucidate the structural mode of self RNA Rmrp-primed TLR3 dimerization and ready for efficient innate recognition on endosomal membrane, extending our knowledge of how membrane-associated TLRs pre-dimerize and suggesting a new function of subcellular localized self RNAs in empowering innate activation.