Protein kinase C (PKC) is a family of phospholipid-dependent serine/threonine kinases that function in numerous different cell types. Based on their structural and activation characteristics, this protein family can be further classified into three subfamilies: conventional or classic PKC isozymes (cPKCs; α, βI, βII, and γ), novel or nonclassic PKC isozymes (nPKCs; δ, ε, η, and θ), and atypical PKC isozymes (aPKCs; ζ, ι, and λ). The activation of cPKCs requires diacylglycerol (DAG) as the primary activator along with phosphatidylserine (PS) and calcium (Ca2+) as cofactors of activation. The nPKCs are also regulated by DAG and PS but do not require Ca2+ for activation. In the case of aPKCs, their activity is stimulated only by PS and not by DAG and Ca2+.

PKC isozymes are involved in multiple signal transduction systems that respond to a variety of external stimulators, including hormones, growth factors, and other membrane receptor ligands. For this reason, PKC isozymes can act as therapeutic targets for several diseases, such as cardiovascular diseases (e.g., atherosclerosis, myocardial fibrosis, cardiac hypertrophy, and hypertension) (for reviews,), immune and inflammatory diseases (e.g., asthma, arthritis, and hepatitis) ,neurological diseases (e.g., Alzheimer’s disease and bipolar disorder) and metabolic disorders (e.g., obesity, insulin resistance, hyperglycemia, and hypercholesterolemia). Further, significant work has also explored the activation, mechanism, and function of PKC isozymes in the development and progression of multiple types of cancer.