Calcium handling in muscle fibres of mice and men: evolutionary adaptation in different species to optimize performance and save energy

摘要

Skeletal muscle fibre specialization is a critical step towards the optimization of the contractile performance. Molecular structure and functional parameters differ among muscle fibres to obtain the best response to specific functional demands. This versatile diversity has been developed during phylogenesis and evolution, but further refinement still occurs during ontogenesis and even in adult life as muscle fibres are endowed with a powerful plasticity. The diversity among muscle fibres, however, has clear borders defined by the consistency between functional parameters and structural features (Schiaffmo & Reggiani, 2011). For example, force generation ability must be matched by the strength of the cytoskeleton, the myo-tendinous connections and the transversal interfibre connections to withstand mechanical stress without damage. Another example is the necessary match between the kinetic properties of calcium-mediated activation, myofibrillar contractile response and metabolic support. Such consistency is required among functional compartments, as well as within each compartment: for example a balance is necessary between the amount of calcium releasable, SERCA activity to take it up and calsequestrin content in order to maintain a low concentration gradient and avoid leakage.