Kinase-dependent Regulation of Inositol 1,4,5-Trisphosphate-dependent Ca2+ Release during Oocyte Maturation*

AUTOR(ES)

Sun, Lu

FONTE

American Society for Biochemistry and Molecular Biology

RESUMO

Fertilization induces a species-specific Ca2+ transient with specialized spatial and temporal dynamics, which are essential to temporally encode egg activation events such as the block to polyspermy and resumption of meiosis. Eggs acquire the competence to produce the fertilization-specific Ca2+ transient during oocyte maturation, which encompasses dramatic potentiation of inositol 1,4,5-trisphosphate (IP3)-dependent Ca2+ release. Here we show that increased IP3 receptor (IP3R) sensitivity is initiated at the germinal vesicle breakdown stage of maturation, which correlates with maturation promoting factor (MPF) activation. Extensive phosphopeptide mapping of the IP3R resulted in ∼70% coverage and identified three residues, Thr-931, Thr-1136, and Ser-114, which are specifically phos pho ryl a ted during maturation. Phospho-specific antibody analyses show that Thr-1136 phos pho ryl a tion requires MPF activation. Activation of either MPF or the mitogen-activated protein kinase cascade independently, functionally sensitizes IP3-dependent Ca2+ release. Collectively, these data argue that the kinase cascades driving meiotic maturation potentiates IP3-dependent Ca2+ release, possibly trough direct phos pho ryl a tion of the IP3R.

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