RyR isoforms and fibre type-specific expression of proteins controlling intracellular calcium concentration in skeletal muscles.

Muscle fibres which shorten with high maximum shortening velocity also exhibit fast kinetics of contraction, i.e. short values of time to peak tension and time to half relaxation. This short review aims to discuss the molecular basis of such correlation, to reach, based on the available literature, an answer to the question whether there is a correlation in expression of proteins determining shortening velocity, myosin isoforms in the first place, and proteins controlling cytosolic calcium concentration and its variations at rest or during contraction. Although the isoforms of RyR, the sarcoplasmic calcium release channels, do not show a tightly coordinated expression with myosin isoforms, other proteins involved in controlling intracellular calcium do. This is likely sufficient to guarantee the correlation between maximum shortening velocity and speed of isometric contraction.