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ECB-ART-37478
Biochem J 2000 Jul 15;349Pt 2:489-99. doi: 10.1042/0264-6021:3490489.
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Activation of protein kinase C alters p34(cdc2) phosphorylation state and kinase activity in early sea urchin embryos by abolishing intracellular Ca2+ transients.

Suprynowicz FA , Groigno L , Whitaker M , Miller FJ , Sluder G , Sturrock J , Whalley T .


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The p34(cdc2) protein kinase, a universal regulator of mitosis, is controlled positively and negatively by phosphorylation, and by association with B-type mitotic cyclins. In addition, activation and inactivation of p34(cdc2) are induced by Ca(2+) and prevented by Ca(2+) chelators in permeabilized cells and cell-free systems. This suggests that intracellular Ca(2+) transients may play an important physiological role in the control of p34(cdc2) kinase activity. We have found that activators of protein kinase C can be used to block cell cycle-related alterations in intracellular Ca(2+) concentration ([Ca(2+)](i)) in early sea urchin embryos without altering the normal resting level of Ca(2+). We have used this finding to investigate whether [Ca(2+)](i) transients control p34(cdc2) kinase activity in living cells via a mechanism that involves cyclin B or the phosphorylation state of p34(cdc2). In the present study we show that the elimination of [Ca(2+)](i) transients during interphase blocks p34(cdc2) activation and entry into mitosis, while the elimination of mitotic [Ca(2+)](i) transients prevents p34(cdc2) inactivation and exit from mitosis. Moreover, we find that [Ca(2+)](i) transients are not required for the synthesis of cyclin B, its binding to p34(cdc2) or its destruction during anaphase. However, in the absence of interphase [Ca(2+)](i) transients p34(cdc2) does not undergo the tyrosine dephosphorylation that is required for activation, and in the absence of mitotic [Ca(2+)](i) transients p34(cdc2) does not undergo threonine dephosphorylation that is normally associated with inactivation. These results provide evidence that intracellular [Ca(2+)](i) transients trigger the dephosphorylation of p34(cdc2) at key regulatory sites, thereby controlling the timing of mitosis entry and exit.

???displayArticle.pubmedLink??? 10880348
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Genes referenced: LOC100887844 LOC115919910 LOC586799 pkcl2

References [+] :
Bitte, Isotopic labeling and analysis of phosphoproteins from mammalian ribosomes. 1974, Pubmed