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bioRxiv · 10.1101/2024.01.12.575391

Loss of calpain 3 dysregulates store-operated calcium entry and its exercise response in mice

Villani, K. R.·Zhong, R.·Henley-Beasley, C. S.·Rastelli, G.·Boncompagni, S.·Barton, E. R.·Wei-LaPierre, L.
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Abstract

Limb-Girdle Muscular Dystrophy 2A (LGMD2A) is caused by mutations in the CAPN3 gene encoding Calpain 3, a skeletal-muscle specific, Ca2+-dependent protease. Localization of Calpain 3 within the triad suggests it contributes to Ca2+ homeostasis. Through live-cell Ca2+ measurements, muscle mechanics, immunofluorescence, and electron microscopy (EM) in Capn3 deficient (C3KO) and wildtype (WT) mice, we determined if loss of Calpain 3 altered Store-Operated Calcium Entry (SOCE) activity. Direct Ca2+ influx measurements revealed loss of Capn3 elicits elevated resting SOCE and increased resting cytosolic Ca2+, supported by high incidence of calcium entry units (CEUs) observed by EM. C3KO and WT mice were subjected to a single bout of treadmill running to elicit SOCE. Within 1HR post-treadmill running, C3KO mice exhibited diminished force production in extensor digitorum longus muscles and a greater decay of Ca2+ transients in flexor digitorum brevis muscle fibers during repetitive stimulation. Striking evidence for impaired exercise-induced SOCE activation in C3KO mice included poor colocalization of key SOCE proteins, stromal-interacting molecule 1 (STIM1) and ORAI1, combined with disappearance of CEUs in C3KO muscles. These results demonstrate that Calpain 3 is a key regulator of SOCE in skeletal muscle and identify SOCE dysregulation as a contributing factor to LGMD2A pathology.

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Villani, K. R., Zhong, R., Henley-Beasley, C. S., Rastelli, G., Boncompagni, S., Barton, E. R., Wei-LaPierre, L.. 2024-01-15. Loss of calpain 3 dysregulates store-operated calcium entry and its exercise response in mice. https://doi.org/10.1101/2024.01.12.575391

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