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Science. 1997 Oct 17;278(5337):471-4.

Inhibition of phosphatases and increased Ca2+ channel activity by inositol hexakisphosphate.

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Rolf Luft Center for Diabetes Research, Department of Molecular Medicine, Karolinska Institute, S-171 76 Stockholm, Sweden.


Inositol hexakisphosphate (InsP6), the dominant inositol phosphate in insulin-secreting pancreatic beta cells, inhibited the serine-threonine protein phosphatases type 1, type 2A, and type 3 in a concentration-dependent manner. The activity of voltage-gated L-type calcium channels is increased in cells treated with inhibitors of serine-threonine protein phosphatases. Thus, the increased calcium channel activity obtained in the presence of InsP6 might result from the inhibition of phosphatase activity. Glucose elicited a transient increase in InsP6 concentration, which indicates that this inositol polyphosphate may modulate calcium influx over the plasma membrane and serve as a signal in the pancreatic beta cell stimulus-secretion coupling.

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