Nutrients Induce Different Ca2+ Signals in Cytosol and Nucleus in Pancreatic β-Cells

Abstract

Specific activation of Ca2+-dependent functions is achieved by the particular dynamics and local restriction of Ca2+ signals. It has been shown that changes in amplitude, duration, or frequency of Ca 2+ signals modulate gene transcription. Thus, Ca2+ variations should be finely controlled within the nucleus. Although a variety of mechanisms in the nuclear membrane have been demonstrated to regulate nuclear Ca2+, the existence of an autonomous Ca2+ homeostasis within the nucleus is still questioned. In the pancreatic β-cell, besides their effect on insulin secretion, Ca2+ messages generated by nutrients also exert their action on gene expression. However, the dynamics of these Ca2+ 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 β-cells were monitored using spot confocal microscopy. We show that nutrients trigger Ca2+ signals of higher amplitude in the nucleus than in the cytosol. These amplitude-modulated Ca2+ signals transmitted to the nucleus might play an important role in the control of gene expression in the pancreatic β-cell.