These findings identify MG29 as a critical regulator of SOCE and lipid signaling in skeletal muscle and suggest that its age-related decline contributes to sarcopenia by disrupting triad membrane organization and excitation–contraction coupling.
Abstract
Sarcopenia is characterized by progressive loss of skeletal muscle mass and function and is a major contributor to frailty, disability, and mortality in older adults. Store-operated calcium entry (SOCE) is a crucial regulator of skeletal muscle calcium homeostasis, and impaired SOCE has been linked to age-related muscle weakness. Here, we identify the synaptophysin family member synaptophysin-like protein 2, also known as mitsugumin 29 (MG29; encoded by the human gene SYPL2 and the mouse ortholog Mg29), as a key organizer of triad membrane cholesterol and lipid signaling required for normal SOCE during aging. Using Mg29−/− mice as a model of accelerated sarcopenia, together with RNA interference against Mg29 in adult muscle and primary myotubes, we quantified changes in muscle morphology, contractile function, SOCE activity, and targeted lipidomic profiles. Reduced MG29 expression led to decreased muscle fiber cross-sectional area, reduced specific force, blunted SOCE, and marked alterations in membrane cholesterol content and fatty acid-derived lipid mediators. Cholesterol depletion by methyl-β-cyclodextrin in wild-type myotubes produced SOCE defects similar to those observed in aged wild-type and young Mg29−/− muscles, indicating that MG29-dependent maintenance of membrane cholesterol is required for normal SOCE. Acute Mg29 knockdown also altered myogenic differentiation, the expression of calcium-handling and stress-response genes, and the release and consumption of specific polyunsaturated fatty acid-derived lipid mediators. Together, these findings identify MG29 as a critical regulator of SOCE and lipid signaling in skeletal muscle and suggest that its age-related decline contributes to sarcopenia by disrupting triad membrane organization and excitation–contraction coupling.
Sarcopenia, the age-related loss of skeletal muscle mass and strength, is a major cause of frailty and disability, with neuromuscular denervation as a key contributor. Bioactive lipid mediators, including lipid hydroperoxides and oxylipins, contribute to denervation-induced muscle atrophy and dysfunction. Here, we identify calcium-independent phospholipase A2β (iPLA2β) as a novel regulator of store-operated calcium ion (Ca2+) entry (SOCE), a critical process for maintaining Ca2+ homeostasis via stromal interaction molecule 1 (STIM1) and Orai1 coupling in skeletal muscle. Using muscle-specific iPLA2β knockout (miPLA2βKO) mice, we show that iPLA2β interacts with STIM1-Orai1 coupling to modulate SOCE. Denervation elevates iPLA2β, hyperactivating SOCE and causing Ca2+ overload through oxidative impairment of regulators such as SERCA. iPLA2β deletion normalizes SOCE, preserves Ca2+ homeostasis, and protects against denervation-induced muscle mass (5%) and strength loss (50%). These findings reveal that iPLA2β may be a critical link between oxidative stress and Ca2+ dysregulation and a promising target for mitigating muscle dysfunction during denervation.
Hongyang Xu, S. Bhaskaran, Jacob L. Brown et al.· Science Advances· 0 citations
Sarcopenia is characterized by the progressive loss of skeletal muscle mass and strength, accompanied by impaired regenerative capacity. This study examined age-related changes in skeletal muscle regeneration and the associated expression of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and myogenin (MyoG). Male C57BL/6 mice aged 3, 13, and 23 months were subjected to barium chloride (BaCl2)-induced tibialis anterior muscle injury. In parallel, C2C12 cells were exposed to repeated low-dose hydrogen peroxide (H2O2) to induce senescence-associated changes under oxidative stress, and the effect of the TWEAK inhibitor L524 was evaluated. Muscle mass and grip strength showed age-dependent declines. Following BaCl2 injury, MyoD expression was induced similarly across age groups, whereas MyoG and embryonic myosin heavy chain expression significantly decreased with advancing age. TWEAK expression increased in injured muscle with age, while p-4E-BP1 showed no clear age-dependent change. In C2C12 cells, repeated H2O2 exposure at 100 μM, which maintained cell viability above 90%, induced senescence-associated changes, reduced myotube formation, increased TWEAK expression, and decreased MyoG expression, whereas treatment with the TWEAK inhibitor L524 attenuated the H2O2-associated reduction in MyoG expression. Collectively, these findings suggest that TWEAK signaling may be associated with oxidative stress and age-related impairments in muscle regeneration.
Jin-Hwa Kim, Hyun-Tae Kim, Jeong-won Kim et al.· Experimental Gerontology· 0 citations
A spatial transcriptomic atlas of skeletal muscle from young and aged mice is presented, resolving transcriptional reprogramming across fiber types and tissue compartments and revealing alterations in sarcomeric organization, excitation-contraction coupling, oxidative stress responses, and fiber type-specific metabolic rewiring.
Veronica Ruggieri, Andrea Bracaglia, Lorenza Esposito et al.· iScience· 0 citations
Age‐related sarcopenia is characterized by a progressive decline in skeletal muscle mass and function, with satellite cell dysfunction representing a central pathogenic mechanism. Diosgenin, a steroidal saponin derived from plants of the Dioscorea genus, has demonstrated potential anti‐aging properties; however, its role in sarcopenia remains unclear. In this study, naturally aged C57BL/6J mice and a D‐galactose (D‐gal)–induced senescent C2C12 cell model were employed to systematically investigate the effects of diosgenin on muscle function, satellite cell dynamics, and the sirtuin 1 (SIRT1)/peroxisome proliferator‐activated receptor gamma coactivator‐1 alpha (PGC‐1α) signaling pathway. Diosgenin treatment significantly improved forelimb grip strength and exercise endurance, increased the gastrocnemius muscle index, and enlarged muscle fiber cross‐sectional area in aged mice. Mechanistically, diosgenin upregulated the expression of myokines meteorin‐like protein (METRNL) and insulin‐like growth factor 1 (IGF‐1) at both mRNA and protein levels, increased the number of proliferative satellite cells positive for paired box 7 (Pax7) and Ki67, and enhanced the expression of myogenic markers, including myogenic factor 5 (Myf5), Pax7, and myosin heavy chain II (MyHC II). These effects were mediated by direct activation of SIRT1, leading to deacetylation of PGC‐1α. Notably, pharmacological inhibition of SIRT1 with EX527 markedly abrogated the diosgenin‐induced effects. Molecular docking and cellular thermal shift assays further confirmed the direct interaction between diosgenin and SIRT1. Collectively, these findings demonstrate that diosgenin alleviates age‐related sarcopenia by activating the SIRT1/PGC‐1α signaling pathway to promote satellite cell proliferation and myogenic differentiation, highlighting its potential as a promising therapeutic candidate for sarcopenia.
Xin Zeng, Han-Wen Ding, Ziye Li et al.· Aging Cell· 0 citations
Background & aims Disuse-induced skeletal muscle atrophy is a major clinical challenge lacking effective targeted therapies. Sarco/endoplasmic reticulum Ca2+-ATPase 2 (SERCA2) is essential for calcium homeostasis in skeletal muscle, but whether its C674 active site contributes to muscle atrophy remains unclear. This study investigated the role of SERCA2 C674 inactivation in skeletal muscle atrophy and the underlying mechanisms. Methods Oxidized SERCA2 (C674–SO3H) expression was assessed in atrophied muscles from bedridden patients and in a murine hindlimb suspension (HLS) model. A SERCA2 C674S knock-in (SKI) mouse model was generated to mimic irreversible oxidation in vivo. Transcriptomic and proteomic analyses, together with in vitro experiments in C2C12 myoblasts and in vivo interventions using Losartan or adeno-associated virus serotype 9 (AAV9)-mediated shRNA, were performed to define downstream signaling pathways and therapeutic potential. Results Total SERCA2 protein levels were unchanged in atrophied muscles from patients and HLS mice, whereas C674–SO3H expression was significantly increased. SKI mice developed spontaneous skeletal muscle atrophy, with reduced myofiber cross-sectional area and impaired muscle strength. Multi-omics analyses showed that SERCA2 dysfunction activated the renin-angiotensin system (RAS)-dependent TGF-β/Smad pathway and markedly upregulated S100a4. Mechanistically, S100a4 interacted with Smad3 and acted as a key downstream effector promoting oxidative stress, inflammation, and muscle protein degradation-related pathways. In vivo treatment with Losartan or AAV9-mediated S100a4 knockdown alleviated local inflammation, fibrosis, and muscle atrophy in both SKI and HLS mice. Conclusions The oxidative inactivation of the SERCA2 C674 site constitutes a novel mechanism driving skeletal muscle atrophy. The SERCA2-RAS-TGF-β/Smad-S100a4 signaling axis emerges as a highly promising therapeutic target for mitigating disuse-induced skeletal muscle wasting.
Fei Nan, Siyao Liu, Shunyi Lei et al.· Redox Biology· 0 citations
Parkinson’s disease (PD) is widely regarded as a disorder of dopaminergic neurons that involves mitochondrial dysfunction, impaired mitophagy, and oxidative stress. However, the nature and significance of skeletal muscle pathology remain unclear. In this study, we used Caenorhabditis elegans, which lack muscle stem cells in adulthood, to examine the effects of PDR-1/Parkin deficiency on mitochondrial homeostasis and motor function under conditions where muscle regeneration does not occur. Silencing of pdr-1 attenuated age-related mitochondrial fragmentation in body-wall muscle cells but was associated with later impairments in locomotor activity and loss of nuclear GFP signals, suggesting progressive muscle cell damage. By day 2 of adulthood, mitochondrial reactive oxygen species (mtROS) levels were elevated in muscle cells subjected to pdr-1 RNAi, and in the pdr-1(gk448) mutant this mtROS elevation was accompanied by a reduction in mitochondrial membrane potential (ΔΨm). In vivo imaging further revealed elevated mitochondrial Ca2+ levels ([Ca2+]mito) in PDR-1-deficient muscle cells. Moreover, the mtROS increase associated with PDR-1 deficiency was suppressed in mcu-1 mutants. These findings support a model in which MCU-1-dependent elevation of [Ca2+]mito contributes to oxidative mitochondrial defects in PDR-1/Parkin-deficient muscle.
Masahiro Kawasumi, Mika Teranishi· Antioxidants· 0 citations