Protein kinase b

Protein kinase B, also known as AKT(Acutely transforming retrovirus AT8 oncogene), is a central component in the metabolic signal transduction of insulin. Active protein kinase B phosphorylates numerous effector proteins.

Upon activation, AKT migrates to the cytoplasm and nucleus where it phosphorylates, activates, or inhibits many downstream targets to regulate various cellular functions. AKT inhibits the GTPase-activating protein (GAP) activity of tuberous sclerosis complex 1 (TSC1) and the TSC2 complex by phosphorylating the TSC2 tuberin protein, leading to the accumulation and activation of the mTOR complex.

In adipose tissue and liver, protein kinase initiates the hydrolysis of cAMP through phosphorylation, leading to a decrease in the intracellular level of cAMP. In the liver, protein kinase B is required for insulin-mediated inhibition of gluconeogenesis. Thus, glycogen synthase 3 is phosphorylated and thus inactivated.

Protein kinase B thus stimulates glycogen synthesis. Insulin in turn leads to the stimulation of protein kinase 3.

In skeletal muscle, protein kinase B phosphorylates the Rab GTPase-activating protein AS160.