PKC

Protein kinase C (PKC) is a family of serine/threonine kinases that regulate a wide range of cellular processes by phosphorylating substrates involved in signal transduction. PKCs respond to diacylglycerol (DAG) and, in the conventional group, to calcium ions, attaching to membranes where many substrates reside. They exist as three major groups based on cofactor requirements: conventional (cPKCs: α, βI, βII, γ), which require both DAG and Ca2+; novel (nPKCs: δ, ε, η, θ), which require DAG but are calcium-independent; and atypical (aPKCs: ζ, ι/λ), which do not depend on DAG or Ca2+.

PKCs are synthesized as inactive cytosolic enzymes that become catalytically competent after maturation through phosphorylation and, upon activation, bind DAG and/or calcium to relieve autoinhibition. The regulatory regions include a C1 domain that binds DAG and phorbol esters, and a C2 domain in some isoforms that mediates calcium-dependent membrane association; the catalytic domain carries the substrate-binding site.

Functionally, PKCs regulate cell proliferation, differentiation, apoptosis, cytoskeletal dynamics, ion channel activity, and transcription factor signaling. They modulate pathways such as NF-κB and AP-1 and participate in insulin signaling, neuronal signaling, and immune responses. Because of their broad influence, PKCs have been implicated in diseases including cancer, cardiovascular disorders, diabetes, and neurodegeneration. Research has pursued isoform-selective inhibitors and activators, though no broad PKC inhibitor is approved for cancer therapy; several agents remain in preclinical or clinical evaluation.

Note: PKC is sometimes used to refer to other concepts in different fields, such as Public Key Cryptography, but in biology it denotes Protein Kinase C.