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During exercise, defects in calcium (Ca2+) release have been proposed to impair muscle function. Here, we show that during exercise in mice and humans, the major Ca2+ release channel required for excitation–contraction coupling (ECC) in skeletal muscle, the ryanodine receptor (RyR1), is progressively PKA-hyperphosphorylated, S-nitrosylated, and depleted of the phosphodiesterase PDE4D3 and the RyR1 stabilizing subunit calstabin1 (FKBP12), resulting in "leaky" channels that cause decreased exercise tolerance in mice.

Mice with skeletal muscle-specific calstabin1 deletion or PDE4D deficiency exhibited significantly impaired exercize capacity. A small molecule (S107) that prevents depletion of calstabin1 from the RyR1 complex improved force generation and exercise capacity, reduced Ca2+-dependent neutral protease calpain activity and plasma creatine kinase levels.

Taken together, these data suggest a possible mechanism by which Ca2+ leak via calstabin1-depleted RyR1 channels leads to defective Ca2+ signaling, muscle damage, and impaired exercise capacity.

Source: Proceedings of the National Academy of Sciences, Feb 12, 2008, vol 105 #6 pp 2198-2202. PMID: 18268335, by Bellinger AM, Marks AR, Reiken S, Dura M, Murphy PW, Deng SX, Landry DW, Nieman D, Lehnart SE, Samaru M, La Campagne A. Columbia University College of Physicians and Surgeons, New York, NY, USA. [E-mail: arm42@columbia.edu]