Biophysical journal最新文献

{"title":"Micromanaging the nuclear lamina.","authors":"Alişya A Anlaş","doi":"10.1016/j.bpj.2025.06.003","DOIUrl":"10.1016/j.bpj.2025.06.003","url":null,"abstract":"","PeriodicalId":8922,"journal":{"name":"Biophysical journal","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144246244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effectiveness of outer hair cells as cochlear amplifier: In simple model systems.","authors":"Kuni H Iwasa","doi":"10.1016/j.bpj.2025.05.029","DOIUrl":"10.1016/j.bpj.2025.05.029","url":null,"abstract":"<p><p>Cochlear outer hair cells (OHCs) have two mechanosensitive elements: the hair bundle (HB) with mechanotrasducer channels and the piezoelectric lateral wall of the cell body. The present report examines how these elements interact with each other by incorporating OHCs into the simplest local cochlear models. In the frequency range, typically above 1 kHz, where capacitive conductance is greater than the ionic conductance, HB conductance drives the piezoelectric cell body and amplified oscillation by countering viscous drag, whereas the cell body increases its stiffness owing to strain-induced polarization, elevating the resonance frequency. Since HB sensitivity is essential for amplification, the resonance is not pure piezoelectric but semi-piezoelectric. In the lower-frequency range, typically lower than 100 Hz, strain-induced polarization contributes to drag, and the HB sensitivity increases cell body stiffness.</p>","PeriodicalId":8922,"journal":{"name":"Biophysical journal","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144233068","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lipid demixing reduces energy barriers for high-curvature vesicle budding.","authors":"Itay Schachter","doi":"10.1016/j.bpj.2024.12.012","DOIUrl":"10.1016/j.bpj.2024.12.012","url":null,"abstract":"<p><p>Under standard physiological conditions, budding relies on asymmetries, including differences in leaflet composition, area, and osmotic conditions, and involves large curvature changes in nanoscale lipid vesicles. So far, the combined impact of asymmetry and high curvatures on budding has remained unknown. Here, using the continuum elastic theory, the budding pathway is detailed under realistic conditions. The model enables a quantitative description of the budding process and the budded state of both ideally and nonideally mixed lipid nanoscale vesicles. It shows that budding is less favored in smaller vesicles but that lipid demixing can significantly reduce its energy barrier, and yet high compositional deviations of more than 7% between the bud and vesicle only occur with phase separation on the bud.</p>","PeriodicalId":8922,"journal":{"name":"Biophysical journal","volume":" ","pages":"1741-1746"},"PeriodicalIF":3.2,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12256894/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142823807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"How SNARE proteins generate force to fuse membranes.","authors":"Ioana C Butu, Dong An, Ben O'Shaughnessy","doi":"10.1016/j.bpj.2025.01.015","DOIUrl":"10.1016/j.bpj.2025.01.015","url":null,"abstract":"<p><p>Membrane fusion is central to fundamental cellular processes such as exocytosis, when an intracellular machinery fuses membrane-enclosed vesicles to the plasma membrane for content release. The core machinery components are the SNARE proteins. SNARE complexation pulls the membranes together, but the fusion mechanism remains unclear. A common view is that the complexation energy drives fusion, but how this energy is harvested for fusion is unexplained. Moreover, SNAREs likely fully assemble before fusion. Computer simulation is challenging, as even fast neurotransmitter release at neuronal synapses involves fusion on ms timescales, beyond the scope of atomistic or mildly coarse-grained approaches. Here, we used highly coarse-grained representations, allowing simulation of the ms timescales of physiological SNARE-driven fusion under physiological conditions. Due to constant collisions, the rod-like SNARE complexes spontaneously generated entropic forces ∼8 pN per SNARE that cleared the fusion site and squeezed the membranes with forces ∼19 pN per SNARE, catalyzing a hemifused stalk connection. Regrouping, five or more SNARE complexes exerted entropic tensions 2.5 pN/nm or greater, expanding the stalk into a hemifusion diaphragm (HD), followed by HD rupture and fusion. The entropic forces generated tensions ∼17-21 pN in the SNARE linker domains (LDs). Previous optical tweezer measurements suggest that, on the ms timescales of fusion, these LD tensions are sufficient to unzipper the LDs while leaving the C-terminal domain (CTD) marginally intact, which are both required for fusion. Consistent with a recent magnetic tweezers study, we propose that the CTD may be further stabilized by complexin for robust fusion. Our results explain how SNARE-generated forces fuse membranes and predict that more SNARE complexes exert higher net force so that fusion is faster, consistent with experimental electrophysiological studies at neuronal synapses. Thus, entropic forces evolve SNARE complexes into a fusogenic, partially unzippered state, squeeze membranes for hemifusion, and expand hemifusion connections for fusion.</p>","PeriodicalId":8922,"journal":{"name":"Biophysical journal","volume":" ","pages":"1815-1827"},"PeriodicalIF":3.2,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12256915/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143036367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dense-core vesicles contain exosomes in secretory cells.","authors":"Xin Wang, Gianvito Arpino, Ammar Mohseni, Christopher K E Bleck, Ling-Gang Wu","doi":"10.1016/j.bpj.2025.01.003","DOIUrl":"10.1016/j.bpj.2025.01.003","url":null,"abstract":"<p><p>Dense-core vesicles (DCVs) are found in various types of cells, such as neurons, pancreatic β- cells, and chromaffin cells. These vesicles release transmitters, peptides, and hormones to regulate diverse functions, such as the stress response, immune response, behavior, and blood glucose levels. In traditional electron microscopy after chemical fixation, it is often reported that the dense cores occupy a portion of the vesicle toward the center and are surrounded by a clear halo. With electron microscopy after cryofixation in adrenal chromaffin cells, we report here that we did not observe halos, but dense cores filling up the entire vesicles suggesting that halos are likely the product of chemical fixation. More importantly, we observed that a fraction of DCVs contained 36-168 nm clear-core vesicles. A similar fraction of DCVs labeled with fluorescent false neurotransmitter FFN 511 or the dense-core matrix protein chromogranin A (CGA) were colocalized with fluorescently labeled or endogenous CD63 or ALIX, the membrane or lumen marker of ∼40-160 nm exosomes. These results suggest that DCVs contain exosomes. Since exosomes are generally thought to reside within multivesicular bodies in the cytosol and are released to the extracellular space to mediate diverse cell-to-cell communications, our findings suggest that DCV fusion from many cell types is a new source for releasing exosomes to mediate intercellular communications. Given that DCV fusion mediates many physiological functions, such as stress responses, immune responses, behavior regulation, and blood glucose regulation, exosome release from DCV fusion might contribute to mediating these important functions.</p>","PeriodicalId":8922,"journal":{"name":"Biophysical journal","volume":" ","pages":"1747-1752"},"PeriodicalIF":3.2,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12256873/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142982588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rab3gap1 palmitoylation cycling modulates cardiomyocyte exocytosis and atrial natriuretic peptide release.","authors":"Kobina Essandoh, Grace A Eramo, Arasakumar Subramani, Matthew J Brody","doi":"10.1016/j.bpj.2025.02.010","DOIUrl":"10.1016/j.bpj.2025.02.010","url":null,"abstract":"<p><p>Rab3 GTPase-activating protein 1 (Rab3gap1) hydrolyzes GTP on Rab3 to inactivate it and reinitiate the Rab3 cycle, which regulates exocytic release of neuropeptides and hormones from neuroendocrine cells and atrial natriuretic peptide (ANP) secretion by cardiomyocytes. Cysteine palmitoylation of Rab3gap1 by the Golgi-localized S-acyltransferase zDHHC9 was recently shown to hinder ANP release by impairing Rab3gap1-mediated nucleotide cycling on Rab3a. Here, we interrogate the cysteine residues of Rab3gap1 modified by palmitoylation and impacts on ANP secretion in cardiomyocytes. Although mutation of the previously identified cysteine (Cys)-678 site of Rab3gap1 alone was insufficient to elicit complete loss of Rab3gap1 palmitoylation in cardiomyocytes, combinatorial mutation of Cys-509, 510, 521, 522, and 678 (Rab3gap1^5CS) dramatically reduced Rab3gap1 palmitoylation. Notably, total cellular GTPase-activating protein (GAP) activity in cardiomyocytes was maintained with mutation of the Rab3gap1 palmitoylation sites as the Rab3gap1^5CS mutant substantially reduced steady-state Rab3a-GTP levels in cardiomyocytes similar to wild-type Rab3gap1. However, although expression of wild-type Rab3gap1 induced robust secretion of ANP and greatly enhanced phenylephrine-stimulated ANP release, the Rab3gap1^5CS palmitoylation-deficient mutant was incapable of promoting exocytosis and ANP release by cardiomyocytes. These data suggest Rab3gap1 cysteine palmitoylation may target Rab3gap1 to Rab3a for regulated GAP-mediated inactivation at specific intracellular membrane domains to modulate the Rab3 cycle and exocytosis. Collectively, these data support a role for Rab3gap1 palmitoylation cycling in spatiotemporal control of the Rab3 cycle to regulate exocytosis and ANP secretion by cardiomyocytes.</p>","PeriodicalId":8922,"journal":{"name":"Biophysical journal","volume":" ","pages":"1843-1855"},"PeriodicalIF":3.2,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12256842/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143424931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The AD3 locus of synaptotagmin-1 C2 domains modulates domain stability.","authors":"Matthew J Dominguez, Anthony A Bui, Johanna Villarreal, Adam Snow, Souvic Karmakar, Faraz M Harsini, Patrick J Rock, Anne M Rice, Kerry L Fuson, R Bryan Sutton","doi":"10.1016/j.bpj.2024.11.009","DOIUrl":"10.1016/j.bpj.2024.11.009","url":null,"abstract":"<p><p>Synaptotagmin-1 (syt1) functions as the Ca²⁺-dependent sensor that triggers the rapid and synchronous release of neurotransmitters from neurotransmitter-containing vesicles during neuronal exocytosis. The syt1 protein has two homologous tandem C2 domains that interact with phospholipids in a Ca²⁺-dependent manner. Despite the crucial role of syt1 in exocytosis, the precise interactions between Ca²⁺, syt1, and phospholipids are not fully understood. In a study involving recessive lethal mutations in the syt1 gene, a specific mutation named AD3 was generated in Drosophila syt1, resulting in a significant reduction in Ca²⁺-dependent exocytosis. Further investigation revealed that the AD3 mutation was a missense mutation located in a conserved consensus sequence within the C2B domain of Drosophila syt1. However, the biophysical impact of the AD3 mutation had not been analyzed. Our study uses x-ray crystallography, isothermal titration calorimetry, thermodynamic analysis, and molecular dynamics simulation to show that the primary defect caused by the AD3 mutation in the syt1 protein is reduced thermodynamic stability. This instability alters the population of Ca²⁺-receptive states, leading to two major consequences: decreased affinity for calcium ions and compromised stabilization of the domain normally enhanced by Ca²⁺. We conclude that this conserved residue acts as a structural constraint, delimiting the movement of loop 3 within the pocket and ultimately influencing the affinity of the calcium ion binding with the C2 domain.</p>","PeriodicalId":8922,"journal":{"name":"Biophysical journal","volume":" ","pages":"1771-1784"},"PeriodicalIF":3.2,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12256881/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142692620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Roles for PKC signaling in chromaffin cell exocytosis.","authors":"Xiaohuan Chen, Nicole A Bell, Breanna L Coffman, David R Giovannucci, Arun Anantharam","doi":"10.1016/j.bpj.2024.12.005","DOIUrl":"10.1016/j.bpj.2024.12.005","url":null,"abstract":"<p><p>Chromaffin cells of the adrenal medulla have an important role in the sympathetic stress response. They secrete catecholamines and other hormones into the bloodstream upon stimulation by the neurotransmitter pituitary adenylate cyclase-activating polypeptide (PACAP). PACAP causes a long-lasting and robust secretory response from chromaffin cells. However, the cellular mechanisms by which PACAP causes secretion remain unclear. Our previous work showed that the secretory response to PACAP relies on signaling through phospholipase C epsilon (PLCε). The objective of this study was to clarify the role of signaling events downstream of PLCε. Here, it is demonstrated that a brief exposure of chromaffin cells to PACAP caused diacylglycerol (DAG) production-a process that was dependent on PLCε activity. DAG then activated protein kinase C (PKC), prompting its redistribution to the plasma membrane. PKC activation was important for the increases in cytosolic Ca²⁺ and exocytosis that were evoked by PACAP. Indeed, pharmacological inhibition of PKC with NPC 15437, a competitive inhibitor of DAG binding, significantly disrupted the secretory response. NPC 15437 application also eliminated PACAP-stimulated effects on the readily releasable pool size, the Ca²⁺ sensitivity of granule fusion, and the voltage dependence of Ca²⁺ channel activation. Quantitative PCR revealed PKCβ, PKCε, and PKCμ to be highly expressed in the mouse chromaffin cell. Genetic knockdown of PKCβ and PKCε disrupted PACAP-evoked secretion, while knockdown of PKCμ had no measurable effect. This study highlights important roles for PKC signaling in a highly regulated pathway for exocytosis that is stimulated by PACAP.</p>","PeriodicalId":8922,"journal":{"name":"Biophysical journal","volume":" ","pages":"1785-1797"},"PeriodicalIF":3.2,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12256897/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142784048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Vesicle docking and fusion pore modulation by the neuronal calcium sensor Synaptotagmin-1.","authors":"Maria Tsemperouli, Sudheer Kumar Cheppali, Félix Rivera-Molina, David Chetrit, Ane Landajuela, Derek Toomre, Erdem Karatekin","doi":"10.1016/j.bpj.2024.12.023","DOIUrl":"10.1016/j.bpj.2024.12.023","url":null,"abstract":"<p><p>Synaptotagmin-1 (Syt1) is a major calcium sensor for rapid neurotransmitter release in neurons and hormone release in many neuroendocrine cells. It possesses two tandem cytosolic C2 domains that bind calcium, negatively charged phospholipids, and the neuronal SNARE complex. Calcium binding to Syt1 triggers exocytosis, but how this occurs is not well understood. Syt1 has additional roles in docking dense-core vesicles (DCVs) and synaptic vesicles to the plasma membrane and in regulating fusion pore dynamics. Thus, Syt1 perturbations could affect release through vesicle docking, fusion triggering, fusion pore regulation, or a combination of these. Here, using a human neuroendocrine cell line, we show that neutralization of highly conserved polybasic patches in either C2 domain of Syt1 impairs both DCV docking and efficient release of serotonin from DCVs. Interestingly, the same mutations resulted in larger fusion pores and faster release of serotonin during individual fusion events. Thus, Syt1's roles in vesicle docking, fusion triggering, and fusion pore control may be functionally related.</p>","PeriodicalId":8922,"journal":{"name":"Biophysical journal","volume":" ","pages":"1798-1814"},"PeriodicalIF":3.2,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12256845/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142885160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fluidic shear stress alters clathrin dynamics and vesicle formation in endothelial cells.","authors":"Tomasz J Nawara, Jie Yuan, Leslie D Seeley, Elizabeth Sztul, Alexa L Mattheyses","doi":"10.1016/j.bpj.2024.06.007","DOIUrl":"10.1016/j.bpj.2024.06.007","url":null,"abstract":"<p><p>Endothelial cells (ECs) experience a variety of highly dynamic mechanical stresses. Among others, cyclic stretch and increased plasma membrane tension inhibit clathrin-mediated endocytosis (CME) in non-ECs. It remains elusive how ECs maintain CME in these biophysically unfavorable conditions. Previously, we have used simultaneous two-wavelength axial ratiometry (STAR) microscopy to show that endocytic dynamics are similar between statically cultured human umbilical vein endothelial cells (HUVECs) and fibroblast-like Cos-7 cells. Here, we asked whether biophysical stresses generated by blood flow influence CME. We used our data processing platform-DrSTAR-to examine if clathrin dynamics are altered in HUVECs after experiencing fluidic shear stress (FSS). We found that HUVECs cultivated under a physiological level of FSS had increased clathrin dynamics compared with static controls. FSS increased both clathrin-coated vesicle formation and nonproductive flat clathrin lattices by 2.3-fold and 1.9-fold, respectively. The curvature-positive events had significantly delayed curvature initiation relative to clathrin recruitment in flow-stimulated cells, highlighting a shift toward flat-to-curved clathrin transitions in vesicle formation. Overall, our findings indicate that clathrin dynamics and clathrin-coated vesicle formation can be modulated by the local physiological environment and represent an important regulatory mechanism.</p>","PeriodicalId":8922,"journal":{"name":"Biophysical journal","volume":" ","pages":"1763-1770"},"PeriodicalIF":3.2,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12256901/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141295456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}