Tuning a Master Kinase: How CaMKII variants are deployed and degraded Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) is a central signaling enzyme that regulates neuronal plasticity, fertilization, and cardiac function. Although its catalytic and oligomerization domains are highly conserved, extensive alternative splicing within a variable linker region generates numerous CaMKII proteoforms whose functional roles remain unclear.