What Is Protein Kinase C?

Protein kinase C (PKC)

Protein kinase C

Protein kinase C (PKC)

Protein kinase C is

10 mammalian tissues have been identified (8-3), which are divided into three groups: A, B, and C. Group A is called classic or conventional PKC (cPKC), including , I, II and subclasses, in which I and have high homology, are formed by different splicing of the same mRNA, and the molecular weight of group A members is 76-78kDa. Group B is a new type of PKC (novel PKC, nPKC), including , , (L) and subclasses, with a molecular weight of 77-83 kDa. Group C is atypical PKC (atypicalPKC, aPKC), which consists of and subclasses, and has a smaller molecular weight of 67 kDa.

Molecular structure of PKC subclass

All subclasses of PKC consist of a single peptide chain (Figure 8-11), with a molecular weight of approximately 67-83 kDa, and their structure can be divided into four conserved regions C1-C4 (mPKC and aPKC lack the C2 region) and five Variable zone V1-V5. The C1 region in the base may be a membrane-bound region and contains a cysteine-rich random repeat sequence Cys-X2-Cys-X13 (14) -Cys-X2-Cys-X7-Cys-X7-Cys (X represents any An amino acid), this sequence is related to many metal-proteins and

Protein kinase C is a cytoplasmic enzyme. In unstimulated cells, PKC is mainly distributed in the cytoplasm in an inactive conformation. Once there is a second messenger, PKC will become a membrane-bound enzyme. It can activate enzymes in the cytoplasm and participate in the regulation of biochemical reactions. It can also act on transcription factors in the nucleus and participate in the regulation of gene expression. Versatile enzyme. ^[3]

Control of glucose metabolism

In liver cells, protein kinase C and protein kinase A cooperate to phosphorylate glycogen synthetase, inhibit glucose-polymerizing enzyme activity, and promote glycogen metabolism

cAMP-mediated promotion of glycogen decomposition and inhibition of glycogen synthesis are caused by the combination of glucagon receptors and -adrenergic receptors with the corresponding hormones; and IP3, DAG, and Ca2 + -mediated promotion of glycogen degradation Glycogen synthesis is caused by alpha-adrenergic receptors and adrenaline. cAMP activates protein kinase A, while IP3, DAG, and Ca2 + activate protein kinase C. ^[2]

Control of cell differentiation

Myogenin is a transcription factor that plays a key role in muscle cell differentiation. In myoblasts, protein kinase C can phosphorylate myogenins, inhibit the ability of myogenins to bind to DNA, and thus prevent cells from differentiating into muscle fibers.

Involved in gene expression regulation

Protein kinase C can participate in the control of gene expression in at least two ways. One way is that protein kinase activates a phosphorylated cascade system that phosphorylates MAP protein kinase. Phosphorylated MAP protein kinase phosphorylates the gene regulatory protein Elk-1 and activates it. Activated Elk-1 binds to a short DNA sequence (called the serum response element, SRE) and then co-regulates gene expression with another factor (the serum response factor, SRF). Another approach is the phosphorylation of protein kinases and activation of the inhibitory protein I-B, which releases the gene regulatory protein NF--B and enters the nucleus to activate the transcription of specific genes. ^[4]

Participation in long-term suppression (LTD)

Long-term cerebellar inhibition of LTD is due to PKC activation indirectly or directly causing phosphorylation of AMPA receptors, which converts AMPA receptors into a stable desensitized state or internalizes the receptors, resulting in LTD ^[5]

Besides

Some people believe that PKC can catalyze proteins that are not catalyzed by other kinases, such as the phosphorylation of proteins involved in secretion and proliferation. It can also activate the Na + -K + exchange system, reduce intracellular H +, increase the pH in the cytoplasm, and improve the operation of the Na + / K + pump. Protein kinase C plays a very important role in cell growth, differentiation, cell metabolism, and transcriptional activation. ^[4] The decrease in PKC activity is also closely related to tumors. ^[3]