Protein kinase C (conventional and novel isoforms) (PKC)

Protein kinase C (PKC) is a family of serine/threonine kinases that play a pivotal role in translating extracellular signals into various cellular responses. The conventional (alpha, beta, gamma) and novel (delta, epsilon, eta, theta) isoforms are specifically defined by their regulatory C1 domains, which serve as the binding site for the lipid second messenger diacylglycerol (DAG) (UniProt: P17252, P05771). Binding of DAG or exogenous ligands like phorbol esters to the C1 domain induces a conformational change that allows the enzyme to translocate to the cell membrane and become catalytically active. Conventional isoforms additionally require calcium for activation, whereas novel isoforms do not. PKC signaling is frequently dysregulated in diseases such as cancer, where it can drive proliferation or survival, and in diabetes, where PKC-beta overactivation contributes to vascular complications (PubMed: 26774338). Therapeutic strategies targeting the C1 domain include the use of bryostatins and ingenol derivatives, which can modulate PKC activity or induce its down-regulation through chronic exposure (PubChem: CID 5311110). This dual mechanism of activation and subsequent degradation makes the C1 domain a unique site for therapeutic intervention in oncology and immunology.

Other names

cPKCnPKCDiacylglycerol-sensitive Protein Kinase CPhorbol ester receptor

Drugs targeting the C1 domain act as molecular mimetics of the second messenger diacylglycerol (DAG), binding to the cysteine-rich C1A or C1B subdomains to induce membrane translocation and activation, which is often followed by the proteolytic down-regulation of the enzyme.