The regulatory domains of cPKC isoforms (cPKCα: cPKC-alpha; cPKCβI: cPKC-beta I, cPKCβII: cPKC-beta II; and cPKCγ: cPKC-gamma) contain a C1 domain consisting of tandem ~50 amino acid long sequences termed C1A and C1B. The C1A and C1B subdomains each have six cysteines and two histidines that coordinate two Zn 2+ ions. The cPKCβII enzyme is an alternatively spliced version of cPKCβI. The C1A/C1B motifs function as a DAG-/PMA-binding motif (PMA: phorbol myristic acid). The regulatory domains of the cPKC isoforms also contain a C2 domain that binds anionic phospholipids in a calcium-dependent manner. All the cPKC isoforms require DAG, Ca 2+ , and phospholipids for activation.
One of the most important functions of cell signaling is to control and maintain normal physiological balance within the body. Activation of different signaling pathways leads to diverse physiological responses, such as cell proliferation, death, differentiation, and metabolism. In the last few years signal transduction therapy has become one of the most important areas of modern drug research. In a healthy organism, the processes of cellular growth and differentiation are tightly controlled, but in the pathological state, are uncoupled in such a way as to result in further damage-causing signals, or the growth of the malfunctioning cells. Proliferation of damaged or malfunctioning cells is often a key factor in the generation of disorders such as cancer , infectious diseases, inflammation, arteriosclerosis, arthritis , and neurodegenerative diseases .