calpain and Sarcopenia

Topics: Aging; Animals; Calcium; Calcium Channels, L-Type; Calpain; Cations, Divalent; Cell Nucleus; Gene Expression Regulation; Humans; Mice; Muscle Strength; Muscle, Skeletal; Muscular Atrophy, Spinal; Ryanodine Receptor Calcium Release Channel; Sarcopenia; Sarcoplasmic Reticulum; Signal Transduction; Sulfonamides; Troponin T

Sarcopenia, the age-related loss of muscle mass, is a highly-debilitating consequence of aging. In this investigation, we show sarcopenia is greatly reduced by muscle-specific overexpression of calpastatin, the endogenous inhibitor of calcium-dependent proteases (calpains). Further, we show that calpain cleavage of specific structural and regulatory proteins in myofibrils is prevented by covalent modification of calpain by nitric oxide (NO) through S-nitrosylation. We find that calpain in adult, non-sarcopenic muscles is S-nitrosylated but that aging leads to loss of S-nitrosylation, suggesting that reduced S-nitrosylation during aging leads to increased calpain-mediated proteolysis of myofibrils. Further, our data show that muscle aging is accompanied by loss of neuronal nitric oxide synthase (nNOS), the primary source of muscle NO, and that expression of a muscle-specific nNOS transgene restores calpain S-nitrosylation in aging muscle and prevents sarcopenia. Together, the findings show that in vivo reduction of calpain S-nitrosylation in muscle may be an important component of sarcopenia, indicating that modulation of NO can provide a therapeutic strategy to slow muscle loss during old age.

Topics: Aging; Animals; Calcium-Binding Proteins; Calpain; Gene Expression; Humans; Mice; Muscle, Skeletal; Myofibrils; Nitric Oxide; Nitric Oxide Synthase Type I; Protein Isoforms; Proteolysis; Sarcopenia

Aging is associated with a progressive and involuntary loss of muscle mass also known as sarcopenia. This condition represents a major public health concern. Although sarcopenia is well documented, the molecular mechanisms of this condition still remain unclear. The calcium-dependent proteolytic system is composed of calcium-dependent cysteine proteases named calpains. Calpains are involved in a large number of physiological processes such as muscle growth and differentiation, and pathological conditions such as muscular dystrophies. The aim of this study was to determine the involvement of this proteolytic system in the phenotype associated with sarcopenia by identifying key proteins (substrates or regulators) interacting with calpains during muscle aging. Immunoprecipitations coupled with proteomic analyses and protein identification by mass spectrometry have been undertaken. Reverse co-immunoprecipitation, cellular colocalisation by confocal microscopy and calpain-dependent in vitro proteolysis of several of the identified proteins have been also carried out. We identified ATP synthase subunit alpha and alpha actinin 3 as key partners of calpains during muscle aging. Such interactions would suggest that calpains are implicated in many processes altered during aging including cytoskeletal disorganisation and mitochondrial dysfunction.

Topics: Actinin; Aging; Animals; Apoptosis; Blotting, Western; Calpain; Gene Expression Regulation, Developmental; Immunoprecipitation; In Situ Nick-End Labeling; Isoenzymes; Male; Muscle Proteins; Muscle, Skeletal; Protein Binding; Proteomics; Proton-Translocating ATPases; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; Ryanodine Receptor Calcium Release Channel; Sarcopenia; Time Factors