Background: Healthy skeletal muscle can undergo structural remodeling following exercise to ensure that intracellular calcium stores and force generation capacity are maintained. This includes T-tubule elongation and Sarcoplasmic Reticulum (SR) formation of flat, parallel stacks to form Calcium Entry Units (CEUs) that enable Store Operated Calcium Entry (SOCE) and underly functional benefits. Muscles from Calpain-3 knockout (C3KO) mice exhibit heightened CEUs at rest, which decrease in abundance after treadmill running. It is unknown which proteins regulate remodeling in healthy skeletal muscle and if and/or how they are affected with loss of CAPN3.
Objective: We used discontinuous density sucrose gradients to enrich for the junctional sarcoplasmic reticulum and utilized liquid chromatography, mass-spectrometry (LC/MS) aimed to identify proteins involved in the SR remodeling in WT and C3KO mice.
Results: LC/MS revealed numerous junctional SR proteins that differ after exercise or loss of CAPN3. Among these hits were four proteins involved in Ca2+ regulation and/or SR/ER stabilization: Store-operated Ca2+ entry regulatory associated factor (SARAF), Calumenin, TMCO1, and Lunapark. Their protein abundance altered with either exercise, loss of CAPN3, or both.
Conclusions: This study provides insight into regulators of healthy skeletal muscle’s exercise response to exercise and a new understanding of proteins affected by loss of CAPN3.
Work was supported by the Coalition to Cure Calpain 3