Downhill Running Decreases the Acetylation of Tubulins and Impairs Autophagosome Degradation in Rat Skeletal Muscle

Abstract

PurposeThis study was designed to probe the effect of downhill running on microtubule acetylation and autophagic flux in rat skeletal muscle.MethodsSprague–Dawley rats were subjected to an exercise protocol of a 90-min downhill run with a slope of −16° and a speed of 16 m·min−1, and then the soleus was sampled at 0, 12, 24, 48, and 72 h after exercise. Protein expression levels of microtubule-associated protein 1 light chain 3 (LC3), p62/sequestosome 1 (p62), α-tubulin, and acetylated α-tubulin (AcK40 α-tubulin) were detected by Western blotting. Alpha-tubulin was costained with AcK40 α-tubulin or cytoplasmic dynein intermediate chain in a single muscle fiber, and LC3 was costained with lysosomal-associated membrane protein 1 in cryosections. To assess autophagic flux in vivo, colchicine or vehicle was injected intraperitoneally 3 d before the exercise experiment, and the protein levels of LC3 and p62 were measured by Western blotting.ResultsDownhill running induced a significant increase in the protein levels of LC3-II and p62, whereas the level and proportion of AcK40 α-tubulin were markedly decreased. Furthermore, the amount of dynein on α-tubulin was decreased after downhill running, and autophagosomes accumulated in the middle of myofibrils. Importantly, LC3-II flux was decreased after downhill running compared with that in the control group.ConclusionsA bout of downhill running decreases microtubule acetylation, which may impair dynein recruitment and autophagosome transportation, causing blocked autophagic flux.

High-intensity interval training alleviates exhaustive exercise-induced HSP70-assisted selective autophagy in skeletal muscle

“…However, in prolonged, strenuous, and eccentric exercise, with the increase in muscle damage and unfolding protein response, proteasome system would be overloaded leading to accumulation of these proteins. So that autophagy might arise for producing more defined degradation targets [ 6 , 7 ]. Under this circumstance, p62 is recruited to bind accumulated substrates and degrade them through selective autophagy [ 8 ].…”