American journal of physiology. Cell physiology最新文献

{"title":"The Theatrics of Collagens in the Myocardium: The Supreme Architect of the Fibrotic Heart.","authors":"Sanchari Chakraborty, Abhi Dutta, Antara Roy, Ashutosh Joshi, Trayambak Basak","doi":"10.1152/ajpcell.01043.2024","DOIUrl":"https://doi.org/10.1152/ajpcell.01043.2024","url":null,"abstract":"<p><p>Heart Failure (HF) mediated by cardiac fibrosis (CF) is characterized with an excessive accumulation of Collagen-based extracellular matrix (ECM) in the myocardium. CF is a common pathophysiological condition in many heart diseases and can be distinctly categorized into two types: replacement and interstitial. In ischemic heart diseases, sudden loss of cardiomyocytes leads to the replacement CF to prevent ventricular rupture. In contrast, excessive collagen deposition in the interstitial space between cardiomyocytes (often in response to pressure overload, chronic cardiac stress, hypertension, etc.) is termed interstitial CF. The progression of HF due to cardiac fibrosis is mainly driven by compromised diastolic function,resulting from increased stiffness of the heart wall muscle due to Collagen-based scar formation. Increased myocardium stiffness is primarily catalyzed by the differential crosslinking of deposited collagens forming the scar in the fibrotic heart. Although collagen deposition remained a hallmark of fibrosis, the pathophysiological progression due to biochemical alterations and mechanistic discrepancy of collagens across cardiac fibrosis subtypes remains elusive. With the advent of next-generation RNA sequencing and high-resolution mass-spectrometry, mechanistic insights into Collagen-mediated scar maturation have gained impetus. A deeper understanding of the spatio-cellular transcriptional heterogeneity and site-specific collagen post-translational modifications (PTMs) in manoeuvring ECM remodeling is gaining attention. The unexplored mechanisms of post-translational modifications and subsequent collagen crosslinking in various cardiac fibrosis may provide the prime target for therapeutic interventions. This review comprehensively summarizes the detailed pattern, role, signaling, and mechanical contributions of different collagens and their PTMs, including crosslinking patterns as newer therapeutic regimens during cardiac fibrosis.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":""},"PeriodicalIF":5.0,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143957996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Serine proteases and protease-activated receptors signaling in the kidney.","authors":"Mykhailo Fedoriuk, Mariia Stefanenko, Ruslan Bohovyk, Marharyta Semenikhina, Joshua H Lipschutz, Alexander Staruschenko, Oleg Palygin","doi":"10.1152/ajpcell.00143.2025","DOIUrl":"https://doi.org/10.1152/ajpcell.00143.2025","url":null,"abstract":"<p><p>Protease-activated receptors (PARs) are a subclass of G protein-coupled receptors activated by serine proteases via proteolytic cleavage, triggering intracellular signaling cascades that regulate various physiological processes. Recent research underscores the significance of serine proteases and PARs in renal physiology, particularly in glomerular cells, where they modulate podocyte function, mesangial matrix dynamics, and filtration barrier integrity. In this review, we discuss the current knowledge on the function of key serine proteases in the kidney, their interactions with specific PARs, with a focus on the glomerulus and pathological implications. Among PARs, PAR1 is the most abundantly expressed in the kidney and plays a pivotal role in renal pathology. Serine proteases such as thrombin, plasmin, and kallikrein interact with PARs to regulate renal function; however, dysregulation in this pathway may contribute to diabetic nephropathy, glomerulosclerosis, fibrosis, and chronic kidney disease. Overall, the role of PARs in glomerular pathophysiology represents a critical area of research with significant therapeutic implications. Continued investigation into the mechanisms of serine proteases and PARs is essential for advancing targeted therapies for glomerular disorders.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":""},"PeriodicalIF":5.0,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143956237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Short-term sustained hypoxia distinctly affects subpopulations of carotid body glomus cells from rats.","authors":"Pedro F Spiller, Henrique J N Morgan, Luiz C C Navegantes, Benedito H Machado, Melina P da Silva, Davi J A Moraes","doi":"10.1152/ajpcell.00967.2024","DOIUrl":"10.1152/ajpcell.00967.2024","url":null,"abstract":"<p><p>The main O₂ arterial chemoreceptors are the carotid bodies (CBs), which mediate hyperventilation in response to short-term sustained hypoxia (SH). CBs contain glomus cells expressing K⁺ channels, which are inhibited by hypoxia, leading to neurotransmitter release. ATP released by CBs and type II cells has been considered essential for chemosensory processing under physiological and pathophysiological conditions. Although the systemic effects of chronic activation of CBs by SH are well known, the early (first 24 h) cellular and molecular mechanisms in CBs as well as the effects of short-term SH on populations of glomus cells are still poorly understood. Here, we show that SH (10% O₂ for 24 h) depolarizes the membrane potential of one population of glomus cells, mediated by increases in inward current, but does not affect the ATP release by CBs. In addition, SH promotes a reduction in their maximum outward current, mediated by voltage-gated K⁺ channels. SH also affected sensitivity to acute hypoxia in one glomus cell subpopulation. As for the content of mitochondrial proteins, we observed increases in the citrate synthase, Tom-20, and succinate dehydrogenase (mitochondrial complex II) per cell of CBs after SH. Our results demonstrate important cellular and molecular mechanisms of plasticity in CBs from rats after only 24 h of SH, which may contribute to the generation of cardiovascular and ventilatory adjustments observed in this experimental model.<b>NEW & NOTEWORTHY</b> Our study revealed two subpopulations of glomus cells of carotid bodies (CBs) with specific electrophysiological properties, which were differentially affected by short-term sustained hypoxia (SH; 10% O₂ for 24 h). Our experiments showed that SH also affected the sensitivity to acute hypoxia of these glomus cell subpopulations differently. Our molecular analyses allowed us to identify important adaptations in the content of CB mitochondrial proteins that participate in the Krebs cycle and form the electron transport chain.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":"C1346-C1365"},"PeriodicalIF":5.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143646948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A mechanism of CALHM1 ion channel gating.","authors":"Zhongming Ma, Usha Paudel, Maria Wang, J Kevin Foskett","doi":"10.1152/ajpcell.00925.2024","DOIUrl":"10.1152/ajpcell.00925.2024","url":null,"abstract":"<p><p>The calcium homeostasis modulator (CALHM) proteins comprise a family of six genes, some of which have been demonstrated to function as ion channels. CALHM1, the founding member, is an extracellular Ca²⁺- and voltage-gated large-pore nonselective ion channel. The mechanisms by which Ca²⁺ and voltage regulate CALHM1 channel gating are unknown. Cryo-electron microscopic structures of CALHM1 and its paralogs have provided little insight into these features, although they have suggested that the amino-termini, including an amino-terminal helix (NTH) and the first transmembrane helix (TM1), may possess significant flexibility. Here, we investigated the role of the amino-terminus in the gating regulation of human CALHM1 channels expressed in <i>Xenopus</i> oocytes. Deletion of the NTH and the proximal end of TM1 markedly reduced the voltage dependence of channel gating, whereas extracellular Ca²⁺ retained the ability to close the channel, indicating that the amino-terminus is not the Ca²⁺-regulated gate. Furthermore, inhibition of channel currents by ruthenium red was independent of the presence of the amino-terminus and was mediated by effects on channel gating rather than pore block. The introduction of a cysteine residue into the proximal end of TM1 enabled complete inhibition of the channel by a cross-linking reagent under conditions in which the channel was in a closed state. Our findings indicate that although the NTH plays a role in voltage-dependent gating, it does not act as the gate itself. Instead, our results suggest that the gate in CALHM1 is formed by proximal regions of the first transmembrane domain.<b>NEW & NOTEWORTHY</b> CALHM1 is a voltage- and extracellular Ca²⁺-regulated large-pore ion channel that plays an essential role in taste perception. The mechanisms that regulate the opening and the closing of the channel are unknown. Here we explored the role of the amino-terminal region of the channel in gating regulation. Our data define the roles of the amino-terminus in channel gating, establishing components essential for the opening and closing of the CALHM1 channel gate.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":"C1109-C1124"},"PeriodicalIF":5.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143466639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transient angiotensin-converting enzyme inhibition confers sex-specific protection against angiotensin II-induced cardiac remodeling.","authors":"Alexandra M Garvin, Dana B Floyd, Alexis C Bailey, Merry L Lindsey, Chad C Carroll, Taben M Hale","doi":"10.1152/ajpcell.00753.2024","DOIUrl":"10.1152/ajpcell.00753.2024","url":null,"abstract":"<p><p>Hypertension increases the prevalence of heart failure to a greater extent in women than men. The fibrotic remodeling of the left ventricle (LV) is a major contributor to increased myocardial stiffness and eventual decrease in cardiac function. Cardiac fibrosis can be prevented in the spontaneously hypertensive rat (SHR) by transient angiotensin-converting enzyme inhibitors (ACEi) in males. Whether transient ACEi also protects against fibrosis in females is not known. In the present study, we evaluated angiotensin II (Ang II)-induced cardiac fibrosis and related signaling in male and female SHR to determine how these responses are altered by prior transient ACEi treatment. Relative changes in blood pressure response to both ACEi and Ang II were similar between sexes, whereas Ang II-induced cardiac hypertrophy was attenuated by prior ACEi in males only. Ang II-induced changes in gene expression for collagens I, III, and IV were attenuated by prior ACEi in males but not females. Despite these sex-specific differences, prior ACEi-attenuated Ang II-induced increases in fibrogenic proteins [phosphorylated SMAD3/SMAD3, periostin, and lysyl oxidase (LOX)] and pro-oxidative proteins (NOX2 and NOX4), as well as hydroxyproline (HYP) content similarly in both sexes. Interestingly, a positive correlation between angiotensin II type 1 (AT1) receptor gene expression and <i>Col1a1</i> in Ang II-treated males is absent in the female SHRs. The observed sex differences in the protection afforded by prior ACEi suggest altered signaling for collagen deposition that may lead to a greater understanding of the sex-dependent efficacy of antihypertensive drugs.<b>NEW & NOTEWORTHY</b> Here, we determine, for the first time that female spontaneously hypertensive rats are responsive to transient angiotensin-converting enzyme inhibitor (ACEi) treatment. Prior work showed that transient ACEi treatment induced persistent protection against a future stimulus in males. Here, Ang II-induced cardiac fibrosis was attenuated by transient ACEi treatment in both sexes. Notably, the underlying mechanism of action is sex-dependent. Specifically, changes in collagen deposition in male but not female hearts correlate with collagen gene expression.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":"C1303-C1317"},"PeriodicalIF":5.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143584380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Functional coupling of Piezo1 channels and Ca²⁺-activated ion channels in the plasma membrane: fine-tunable interplay with wide-range signaling effects.","authors":"Valeriia Y Vasileva, Anastasia V Sudarikova, Vladislav I Chubinskiy-Nadezhdin","doi":"10.1152/ajpcell.00094.2025","DOIUrl":"10.1152/ajpcell.00094.2025","url":null,"abstract":"<p><p>Ca²⁺ is a universal second messenger in living cells, and its concentration should be precisely localized to provide the outstanding specificity of signal transduction. The conception of Ca²⁺ micro- and nanodomains in which Ca²⁺ ions could control the activity of various Ca²⁺-dependent molecules was postulated: the Ca²⁺-permeable ion channels in the plasma membrane provide a pathway for Ca²⁺ entry from the extracellular milieu into the cytosol regulating the activity of Ca²⁺-dependent molecules, that is, functionally colocalized Ca²⁺-activated ion channels. These channel complexes of different molecular compositions were observed in the cells of different origins; thus, the phenomenon of ion channel coupling is thought to be a universal property of living cells. Piezo1 is a mechanosensitive Ca²⁺-permeable ion channel that plays a pivotal role in cellular mechanotransduction and is integrated into various signaling cascades regulating the activity of Ca²⁺-dependent molecules. Here, we summarized recent experimental data on the presence and role of functional complexes of Piezo1 with Ca²⁺-activated channels of different origins and highlighted the complex molecular mechanisms that could control the channel coupling in the plasma membrane.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":"C1338-C1345"},"PeriodicalIF":5.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143656087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The vitamin D₃ hormone, 1,25(OH)₂D₃, regulates fibroblast growth factor 23 (FGF23) production in human skin cells.","authors":"Franz Ewendt, Zorica Janjetovic, Tae-Kang Kim, Alisa A Mobley, Anna A Brożyna, Senthilkumar Ravichandran, Adrian Fabisiak, Pawel Brzeminski, Rafal R Sicinski, Gabriele I Stangl, Robert C Tuckey, Andrzej T Slominski","doi":"10.1152/ajpcell.00827.2024","DOIUrl":"10.1152/ajpcell.00827.2024","url":null,"abstract":"<p><p>The bone hormone fibroblast growth factor 23 (FGF23) regulates renal phosphate reabsorption and the enzymatic production of active vitamin D₃ [1,25(OH)₂D₃]. Therefore, FGF23 production in bone cells is closely regulated by 1,25(OH)₂D₃ acting via the vitamin D receptor (VDR). Skin cells can produce hydroxyvitamin D₃ metabolites from its precursor D₃ made through ultraviolet B light exposure. Interestingly, the expression of Fgf23 has been found in rodent skin, but its expression, regulation, and role in human skin are unclear. Therefore, we investigated whether hydroxyvitamin D₃ metabolites regulate FGF23 in human skin cells. Primary adult and neonatal epidermal keratinocytes (HEKn), melanocytes (HEMn), dermal fibroblasts (HDFn), as well as human melanoma cells, HaCaT, HaCaT VDR KO, and A431 epidermoid cells, were used to assess <i>FGF23</i> gene expression (quantitative reverse-transcription real-time PCR), cellular FGF23 protein (Western blot), or secreted FGF23 protein (ELISA) after treatment with hydroxyvitamin D₃ metabolites. HaCaT cells treated with recombinant FGF23 were used to explore its function in skin. Human skin cells can synthesize FGF23. Treatment with 1,25(OH)₂D₃ significantly increased <i>FGF23</i> mRNA levels in HaCaT and HDFn cells, and moderately in HEKn cells, mediated in part by the VDR. It also moderately enhanced mRNA levels of the FGF23-processing enzyme <i>GALNT3</i> and stimulated secretion of hormonally active FGF23 from HaCaT cells. Treatment of HaCaT cells with FGF23 increased mRNA levels of the cholesterol- and vitamin D-metabolizing enzymes, <i>CYP11A1</i> and <i>CYP27A1</i>. In conclusion, human skin cells express and secrete FGF23, which is regulated by 1,25(OH)₂D₃ acting in part by the VDR. FGF23 affects the expression of cutaneous sterol-metabolizing enzymes.<b>NEW & NOTEWORTHY</b> This study shows for the first time the expression and secretion of the FGF23 hormone by human skin cells. In addition, we identified the active vitamin D₃ hormone, 1,25(OH)₂D₃, to be a potent regulator of dermal FGF23 expression and protein secretion, partly involving the vitamin D receptor. Furthermore, we provide initial evidence demonstrating that FGF23 upregulates the gene expression of <i>CYP11A1</i> and <i>CYP27A1</i> in keratinocytes.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":"C1177-C1192"},"PeriodicalIF":5.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143584310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dysfunctional mitochondrial bioenergetics sustains drug resistance in cancer cells.","authors":"Davide Gnocchi, Dragana Nikolic, Silvia Russo, Maria Laura Matrella, Rosa R Paparella, Sujeet Kumar, Subhas S Karki, Carlo Sabbà, Tiziana Cocco, Simona Lobasso, Antonio Mazzocca","doi":"10.1152/ajpcell.00538.2024","DOIUrl":"10.1152/ajpcell.00538.2024","url":null,"abstract":"<p><p>Resistance to drugs is one of the major issues affecting the response to pharmacological treatments for tumors. Different mechanisms have been proposed to explain the development of cancer drug resistance (CDR), and several approaches to overcome it have been suggested. However, the biological basis of CDR remains unclear. Here, we investigated whether mitochondrial damage and consequent mitochondrial dysfunction are major causes of drug resistance in different tumors. To this end, we used cell lines from three tumors: hepatocellular carcinoma, breast cancer, and colon cancer. We then applied a protocol that recapitulates chemotherapy regimens in patients, rendering each cell line resistant to the drug commonly used in their respective treatments. The combination of cellular respiration analysis, gene expression analysis of cytochrome c oxidase isoforms, and mass spectrometry assessment of cardiolipin (CL) reveals that mitochondrial dysfunction is the underlying cause of the resistant phenotype. Importantly, we disclosed for the first time the rapid inhibition of oxidative phosphorylation (OXPHOS) by l-lactate, the major product of fermentation. Finally, we demonstrated that inhibition of lactic acid fermentation and activation of OXPHOS can increase drug sensitivity in all tested drug-resistant cancer cells. Taken together, our results suggest that inhibiting fermentation and enhancing mitochondrial function in cancer cells may be a concrete option to control the worrisome phenomenon of CDR.<b>NEW & NOTEWORTHY</b> Cancer drug resistance (CDR) is increasingly becoming a concerning clinical problem. The mechanisms behind the onset of CDR are still not well defined. In this study, we demonstrated that a treatment mimicking long-term clinical protocols with commonly used chemotherapeutic agents promotes mitochondrial bioenergetic dysfunction, leading to the acquisition of CDR. In a future perspective, interventions aimed at inhibiting fermentation and restoring OXPHOS efficiency may offer tangible opportunities to reduce the clinical burden of CDR.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":"C1150-C1159"},"PeriodicalIF":5.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143031716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cellular and molecular contractile function in aged human skeletal muscle is altered by phosphate and acidosis and partially reversed with an ATP analog.","authors":"Aurora D Foster, Chad R Straight, Philip C Woods, Christopher Lee, Jane A Kent, Stuart R Chipkin, Edward P Debold, Mark S Miller","doi":"10.1152/ajpcell.00332.2024","DOIUrl":"10.1152/ajpcell.00332.2024","url":null,"abstract":"<p><p>Skeletal muscle fatigue occurs, in part, from the accumulation of hydrogen (H⁺) and phosphate (P_i); however, the molecular basis through which these ions inhibit function is not fully understood. Therefore, we examined the effects of these metabolites on myosin-actin cross-bridge kinetics and mechanical properties in skeletal muscle fibers from older (65-75 yr) adults. Slow-contracting myosin heavy chain (MHC) I and fast-contracting MHC IIA fibers were examined under control (5 mM P_i, pH 7.0) and fatigue (30 mM P_i, pH 6.2) conditions at maximal calcium-activation [5 mM adenosine triphosphate (ATP)] and rigor (0 mM ATP). In MHC I and IIA fibers, fatigue decreased force per fiber size (23%-37%), which was accompanied by reduced strongly bound myosin head characteristics (number and/or stiffness; 21%-47%) and slower cross-bridge kinetics [longer myosin attachment times (22%-46%) and reduced rates of force production (20%-33%)] compared with control. MHC I myofilaments became stiffer with fatigue, a potential mechanism to increase force production. In rigor, which causes the myosin that can bind actin to be strongly bound, fatigue decreased force per fiber size (32%-33%) in MHC I and IIA fibers, indicating less force was generated per cross bridge. By replacing ATP with 2-deoxy-ATP, the fatigue-induced slowing of cross-bridge kinetics in MHC I and IIA fibers was reversed, and reduced force production in MHC I fibers was partially improved, revealing potential mechanisms to help mitigate fatigue in older adults. Overall, our results identify novel fiber type-specific changes in cross-bridge kinetics, force per cross bridge, and myofilament stiffness that help explain fatigue in older adults.<b>NEW & NOTEWORTHY</b> Skeletal muscle fatigue is caused, in part, by increased production of phosphate and hydrogen ions, resulting in decreased force generation. We found that reduced force in fibers from older adults was due to altered function of myosin and actin, including slower protein interactions and reduced force per myosin head. Additionally, an ATP analog, dATP, partially reversed contractile dysfunction induced by increased phosphate and hydrogen, improving force production and altering myosin-actin interactions dependent upon fiber type.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":"C1220-C1233"},"PeriodicalIF":5.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143565776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Activity and function of the endothelial sodium channel is regulated by the effector domain of MARCKS-like protein 1 in mouse aortic endothelial cells.","authors":"Ling Yu, Niharika Bala, Van-Anh L Nguyen, Leah Kessler, John F LaDisa, Abdel A Alli","doi":"10.1152/ajpcell.00425.2024","DOIUrl":"10.1152/ajpcell.00425.2024","url":null,"abstract":"<p><p>Enhanced endothelial sodium channel (EnNaC) functioning causes an increase in vessel stiffness. Here, we investigated the regulation of EnNaC in mouse aortic endothelial cells (mAoECs) by the actin cytoskeleton and lipid raft association protein myristoylated alanine-rich C-kinase substrate-like protein 1 (MLP1). We hypothesized that mutation of specific amino acid residues within the effector domain of MLP1 or loss of association between MLP1 and the anionic phospholipid phosphate PIP2 would significantly alter membrane association and EnNaC activity in mAoECs. mAoECs transiently transfected with a mutant MLP1 construct (three serine residues in the effector domain replaced with aspartate residues) showed a significant decrease in EnNaC activity compared with cells transfected with wild-type MLP1. Compared with vehicle treatment, mAoECs treated with the PIP2 synthesis blocker wortmannin showed less colocalization of EnNaC and MLP1. In other experiments, Western blot and densitometric analysis showed a significant decrease in MLP1 and caveolin-1 protein expression in mAoECs treated with wortmannin compared with vehicle. Finally, wortmannin treatment decreased sphingomyelin content and increased membrane fluidity in mAoECs. Taken together, these results suggest that constitutive phosphorylation of MLP1 attenuates the function of EnNaC in aortic endothelial cells by a mechanism involving a decrease in association with MLP1 and EnNaC at the membrane, whereas deletion of PIP2 decreases MLP1 expression and overall membrane fluidity.<b>NEW & NOTEWORTHY</b> In this study, we investigated the functional role of myristoylated alanine-rich C-kinase substrate-like protein 1 (MLP1) phosphorylation in regulating endothelial sodium channel (EnNaC) activity using mouse aortic endothelial cells for the first time. The results from this study will help elucidate the molecular mechanism by which aortic stiffness is regulated by EnNaC.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":"C1101-C1108"},"PeriodicalIF":5.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143466698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}