Sisters Acts: Converging Signaling Between CaMKII and CaMKIV, Two Members of the Same Family

Calcium (Ca(2+)) is a universal second messenger that regulates a number of diverse cellular processes including cell proliferation, development, motility, secretion, learning and memory1, 2. A variety of stimuli, such as hormones, growth factors, cytokines, and neurotransmitters induce changes in the intracellular levels of Ca(2+). The most ubiquitous and abundant protein that serves as a receptor to sense changes in Ca(2+) concentrations is Calmodulin (CaM), thus mediating the role as second messenger of this ion. The Ca(2+)/CaM complex initiates a plethora of signaling cascades that culminate in alteration of cell functions. Among the many Ca(2+)/CaM binding proteins, the multifunctional protein kinases CaMKII and CaMKIV play pivotal roles in the cell.