The regulation and activities of the multifunctional serine/threonine kinase Akt/PKB

The serine/threonine kinase Akt, or protein kinase B (PKB), has recently be en a focus of intense research. It appears that Akt/PKB lies in the crossro ads of multiple cellular signaling pathways and acts as a transducer of man y functions initiated by growth factor receptors that activate phosphatidyl inositol 3-kinase (PI 3-kinase). Akt/PKB is particularly important in media ting several metabolic actions of insulin. Another major activity of Akt/PK B is to mediate cell survival. In addition, the recent discovery of the tum or suppressor PTEN as an antagonist of PI 3-kinase and Akt/PKB kinase activ ity suggests that Akt/PKB is a critical factor in the genesis of cancer. Th us, elucidation of the mechanisms of Akt/PKB regulation and its physiologic al functions should be important for the understanding of cellular metaboli sm, apoptosis, and cancer. (C) 1999 Academic Press.