Regulation by phosphorylation of reversible association of a myristoylated protein kinase C substrate with the plasma membrane.

Protein kinase C (PKC) transduces receptor-mediated signals by phosphorylating membrane-bound substrates which then act as effectors of specific cellular responses. The myristoylated alanine-rich C kinase substrate (MARCKS) is a specific PKC substrate which has been implicated in macrophage activation, neuro-secretion and growth factor-dependent mitogenesis. Myristoylation of MARCKS is required for effective binding to the plasma membrane where it colocalizes with PKC. Here we report that PKC-dependent phosphorylation displaces MARCKS from the membrane and that its subsequent dephosphorylation is accompanied by its reassociation with the membrane. This cycle of phosphorylation-dependent membrane attachment and detachment of a myristoylated protein represents a novel mechanism of reversible membrane targeting. As MARCKS is a calmodulin- and actin-binding protein (ref. 8, and J. Hartwig et al., manuscript submitted), the cycle of membrane attachment/detachment represents a mechanism through which PKC might reversibly regulate actin-membrane interaction.