Conventional PKCs regulate the temporal pattern of Ca²⁺ oscillations at fertilization in mouse eggs

In mammalian eggs, sperm-induced Ca²⁺ oscillations at fertilization are the primary trigger for egg activation and initiation of embryonic development. Identifying the downstream effectors that decode this unique Ca²⁺ signal is essential to understand how the transition from egg to embryo is coordinated. Here, we investigated whether conventional PKCs (cPKCs) can decode Ca²⁺ oscillations at fertilization. By monitoring the dynamics of GFP-labeled PKCα and PKCγ in living mouse eggs, we demonstrate that cPKCs translocate to the egg membrane at fertilization following a pattern that is shaped by the amplitude, duration, and frequency of the Ca²⁺ transients. In addition, we show that cPKC translocation is driven by the C2 domain when Ca²⁺ concentration reaches 1–3 μM. Finally, we present evidence that one physiological function of activated cPKCs in fertilized eggs is to sustain long-lasting Ca²⁺ oscillations, presumably via the regulation of store-operated Ca²⁺ entry.