The role of Ca2+and calmodulin in insulin signalling in mammalian skeletal muscle

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Abstract
The role of Ca2+ in mediating effects of insulin on skeletal muscle has been widely debated. It is believed that in skeletal muscle Ca2+ has a permissive role, necessary but not of prime importance in mediating the stimulatory actions of insulin. In this review, we present evidence that insulin causes a localized increase in the concentration of Ca2+. Specifically, insulin induces a rise in near‐membrane Ca2+ but not the bulk Ca2+ in the myoplasm. The rise in near‐membrane Ca2+ is because of an influx through channels that can be blocked by L‐type Ca2+ channel inhibitors. Calcium appears to exert some of its subsequent effects via calmodulin‐dependent processes as calmodulin inhibitors block the translocation of glucose transporters and other enzymes as well as the insulin‐stimulated increase in glucose transport.