|Bovine, Chicken, D. melanogaster, Dog, Guinea Pig, Hamster, Human, Monkey, Mouse, Pig, Rat|
Application Methods: Flow Cytometry, Immunofluorescence (Immunocytochemistry), Immunoprecipitation, Western Blotting
Background: Akt, also referred to as PKB or Rac, plays a critical role in controlling survival and apoptosis (1-3). This protein kinase is activated by insulin and various growth and survival factors to function in a wortmannin-sensitive pathway involving PI3 kinase (2,3). Akt is activated by phospholipid binding and activation loop phosphorylation at Thr308 by PDK1 (4) and by phosphorylation within the carboxy terminus at Ser473. The previously elusive PDK2 responsible for phosphorylation of Akt at Ser473 has been identified as mammalian target of rapamycin (mTOR) in a rapamycin-insensitive complex with rictor and Sin1 (5,6). Akt promotes cell survival by inhibiting apoptosis through phosphorylation and inactivation of several targets, including Bad (7), forkhead transcription factors (8), c-Raf (9), and caspase-9. PTEN phosphatase is a major negative regulator of the PI3 kinase/Akt signaling pathway (10). LY294002 is a specific PI3 kinase inhibitor (11). Another essential Akt function is the regulation of glycogen synthesis through phosphorylation and inactivation of GSK-3α and β (12,13). Akt may also play a role in insulin stimulation of glucose transport (12). In addition to its role in survival and glycogen synthesis, Akt is involved in cell cycle regulation by preventing GSK-3β-mediated phosphorylation and degradation of cyclin D1 (14) and by negatively regulating the cyclin dependent kinase inhibitors p27 Kip1 (15) and p21 Waf1/Cip1 (16). Akt also plays a critical role in cell growth by directly phosphorylating mTOR in a rapamycin-sensitive complex containing raptor (17). More importantly, Akt phosphorylates and inactivates tuberin (TSC2), an inhibitor of mTOR within the mTOR-raptor complex (18,19).
|Guinea Pig, Human, Mouse|
Application Methods: Western Blotting
Background: Mammalian sterile-20-like (MST) kinases are upstream regulators of mitogen-activated protein kinase (MAPK) signaling pathways that regulate multiple cellular processes, including proliferation, apoptosis, migration, and cytoskeletal rearrangement (1). This family of serine/threonine kinases includes MST1 (STK4) and MST2 (STK3), two functionally related proteins with conserved amino-terminal kinase domains and carboxy-terminal regulatory domains that contain nuclear export signals (1-3). During apoptosis, caspase-mediated cleavage of MST1/2 removes the inhibitory regulatory domain, triggering autophosphorylation and activation of the kinase domain, which is translocated to the nucleus. Nuclear translocation of the active kinase induces chromatin condensation and other events associated with apoptotic progression (4).Research studies indicate that MST1/2 are orthologous to Drosophila Hippo (Hpo), one of the core regulatory proteins in the Hippo signaling pathway. This evolutionarily conserved program controls tissue growth and organ size by regulating cell proliferation, apoptosis, and stem cell self-renewal. The mammalian Hippo signaling pathway involves a kinase cascade, where the MST1/2 kinases and the SAV1 scaffold protein form a complex that leads to phosphorylation and activation of LATS1/2. The LATS1/2 kinases phosphorylate YAP and TAZ, promoting cytoplasmic sequestration and inhibition of these transcription coactivators (5).