Nutrients induce different Ca(2+) signals in cytosol and nucleus in pancreatic beta-cells.

Abstract

Specific activation of Ca(2+)-dependent functions is achieved by the particular dynamics and local restriction of Ca(2+) signals. It has been shown that changes in amplitude, duration, or frequency of Ca(2+) signals modulate gene transcription. Thus, Ca(2+) variations should be finely controlled within the nucleus. Although a variety of mechanisms in the nuclear membrane have been demonstrated to regulate nuclear Ca(2+), the existence of an autonomous Ca(2+) homeostasis within the nucleus is still questioned. In the pancreatic beta-cell, besides their effect on insulin secretion, Ca(2+) messages generated by nutrients also exert their action on gene expression. However, the dynamics of these Ca(2+) signals in relation to nuclear function have been explored little in islet cells. In the current study, Ca(2+) changes both in the nucleoplasm and in the cytosol of INS-1 and pancreatic beta-cells were monitored using spot confocal microscopy. We show that nutrients trigger Ca(2+) signals of higher amplitude in the nucleus than in the cytosol. These amplitude-modulated Ca(2+) signals transmitted to the nucleus might play an important role in the control of gene expression in the pancreatic beta-cell.