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XB-ART-55421
EMBO Rep 2018 Dec 01;1912:. doi: 10.15252/embr.201846433.
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Calcineurin promotes APC/C activation at meiotic exit by acting on both XErp1 and Cdc20.

Heim A, Tischer T, Mayer TU.


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Vertebrate oocytes await fertilization arrested at metaphase of the second meiotic division. Fertilization triggers a transient calcium wave, which induces the activation of the anaphase-promoting complex/cyclosome (APC/C) and its co-activator Cdc20 resulting in the destruction of cyclin B and hence meiotic exit. Two calcium-dependent enzymes are implicated in fertilization-induced APC/CC dc20 activation: calcium-/calmodulin-dependent kinase type II (CaMKII) and calcineurin (CaN). While the role of CaMKII in targeting the APC/C inhibitor XErp1/Emi2 for destruction is well-established, it remained elusive how CaN affects APC/CC dc20 activation. Here, we discover that CaN contributes to APC/CC dc20 activation in Xenopus laevis oocytes by two independent but interrelated mechanisms. First, it facilitates the degradation of XErp1 by dephosphorylating it at a site that is part of a phosphorylation-dependent recruiting motif for PP2A-B'56, which antagonizes inhibitory phosphorylation of XErp1. Second, it dephosphorylates Cdc20 at an inhibitory site, thereby supporting its APC/C-activating function. Thus, our comprehensive analysis reveals that CaN contributes to timely APC/C activation at fertilization by both negatively regulating the APC/C inhibitory activity of XErp1 and positively regulating the APC/C-activating function of Cdc20.

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Species referenced: Xenopus laevis
Genes referenced: camk2g cdc20 fbxo43 ppp3ca ptpa
GO keywords: anaphase-promoting complex [+]

References [+] :
Busa, An elevated free cytosolic Ca2+ wave follows fertilization in eggs of the frog, Xenopus laevis. 1985, Pubmed, Xenbase