Contractile Proteins and Pancreatic Beta-cell Secretion

Much indirect evidence suggests, but does not prove, that insulin secretion depends on contractile proteins similar to those of skeletal muscle and cilia. Such proteins constitute a molecular basis for the emiocytotic extrusion of insulin granules. It is likely that the secretory machinery is complex, requiring over eight proteins. The available evidence is consistent with a model of saltatory granule movement oriented by microtubules and powered by actomyosin contraction in response to elevations in cytosol calcium. Because most diabetics secrete some insulin and because relatively little of the stored B-cell insulin is released in response to hyperglycemia, further research into the molecular mechanism of insulin granule release is needed.