Development of a new model system to dissect isoform specific Akt signaling in adipocytes

Akt kinases are critical signal transducers mediating insulin action. Genetic studies revealed that Akt1 and Akt2 signaling differentially contribute to sustain lipid and glucose homeostasis; howeverAkt isoform-specific effectors remain elusive due to the lack of a suitable model system to mechanistically interrogate Akt isoform-specific signaling. To overcome those technical limitations we developed a novel model system that provides acute and specific control of signaling by Akt isoforms. We generated mutants of Akt1 and Akt2 resistant to the allosteric Akt inhibitor MK-2206. We then developed adipocyte cell lines, in which endogenous Akt1 or Akt2 has been replaced by their corresponding drug-resistant Akt mutant. Treatment of those cells with MK-2206 allowed for acute and specific control of either Akt1 or Akt2 function. Our data showed that Akt1W80A and Akt2W80A mutants are resistant to MK-2206, dynamically regulated by insulin and able to signal to Akt downstream effectors. Analyses of insulin action in this cellular system showed that Akt1 and Akt2 are both able to mediate insulin regulation of the transcription factor FoxO1 and the glucose transporter GLUT4, revealing a redundant role for these Akt kinases in the control of glucose transport into fat cells. In contrast, Akt1 signaling is uniquely required for adipogenesis, by controlling the mitotic clonal expansion of preadipocytes that precedes white adipose cell differentiation. Our data provide new insights into th...
Source: BJ Signal - Category: Biochemistry Authors: Tags: BJ Signal Source Type: research