Inositol 1,4,5-trisphosphate receptor 1, a widespread Ca2+ channel, is a novel substrate of polo-like kinase 1 in eggs

Abstract To initiate embryo development, the sperm induces in the egg release of intracellular calcium ([Ca 2+ ] i ). During oocyte maturation, the inositol 1,4,5-trisphosphate receptor (IP 3 R1), the channel implicated, undergoes modifications that enhance its function. We found that IP 3 R1 becomes phosphorylated during maturation at an MPM-2 epitope and that this persists until the fertilization-associated [Ca 2+ ] i responses cease. We also reported that maturation without ERK activity diminishes IP 3 R1 MPM-2 reactivity and [Ca 2+ ] i responses. Here, we show that IP 3 R1 is a novel target for Polo-like kinase1 (Plk1), a conserved M-phase kinase, which phosphorylates it at an MPM-2 epitope. Plk1 and IP 3 R1 interact in an M-phase preferential manner, and they exhibit close co-localization in the spindle/spindle poles area. This co-localization is reduced in the absence of ERK activity, as the ERK pathway regulates spindle organization and IP 3 R1 cortical re-distribution. We propose that IP 3 R1 phosphorylation by Plk1, and possibly by other M-phase kinases, underlies the delivery of spatially and temporally regulated [Ca 2+ ] i signals during meiosis/mitosis and cytokinesis.