An inositol 1,4,5-trisphosphate-sensitive Ca2+ pool in liver nuclei.

AUTOR(ES)

Nicotera, P

RESUMO

Recent studies in our laboratory have revealed the existence of an ATP- and calmodulin-dependent Ca2+ uptake system in rat liver nuclei that can promote increases in the free Ca2+ concentration in the nuclear matrix. In the present investigation we show that liver nuclei possess a marked ability to sequester and buffer Ca2+, suggesting a potential role for the nucleus in the regulation of the cytosolic free Ca2+ concentration. In addition, we demonstrate that the intracellular messenger, inositol 1,4,5-trisphosphate [Ins-(1,4,5)P3], stimulates the release of a fraction of the nuclear Ca2+ and transiently lowers the intranuclear free Ca2+ concentration. The Ins(1,4,5)P3-stimulated Ca2+ release is followed by Ca2+ reuptake into an inositol phosphate-insensitive nuclear compartment. Together, these results demonstrate that liver nuclei contain, at least, two Ca2+ pools, one of which is releasable by Ins(1,4,5)P3. These findings are consistent with a role for the nucleus in the modulation of the cytosolic free Ca2+ level by agonists and suggest that the control of the nuclear Ca2+ load by second messengers may participate in the regulation of intranuclear Ca2(+)-dependent processes by hormones and other agents.

Documentos Relacionados

• Inositol 1,4,5-trisphosphate-sensitive Ca2+ release across nonvacuolar membranes in cauliflower.
• "Calciosome," a cytoplasmic organelle: the inositol 1,4,5-trisphosphate-sensitive Ca2+ store of nonmuscle cells?
• Diffusion of inositol 1,4,5-trisphosphate but not Ca2+ is necessary for a class of inositol 1,4,5-trisphosphate-induced Ca2+ waves.
• Technique for in situ measurement of calcium in intracellular inositol 1,4,5-trisphosphate-sensitive stores using the fluorescent indicator mag-fura-2.
• Inositol 1,4,5-tris-phosphate activation of inositol tris-phosphate receptor Ca2+ channel by ligand tuning of Ca2+ inhibition