BSTA promotes mTORC2-mediated phosphorylation of Akt1 to suppress expression of FoxC2 and stimulate adipocyte differentiation.

Science signaling 2013 Jan 08

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Phosphorylation and activation of Akt1 is a crucial signaling event that promotes adipogenesis. However, neither the complex multistep process that leads to activation of Akt1 through phosphorylation at Thr³⁰⁸ and Ser⁴⁷³ nor the mechanism by which Akt1 stimulates adipogenesis is fully understood. We found that the BSD domain-containing signal transducer and Akt interactor (BSTA) promoted phosphorylation of Akt1 at Ser⁴⁷³ in various human and murine cells, and we uncovered a function for the BSD domain in BSTA-Akt1 complex formation. The mammalian target of rapamycin complex 2 (mTORC2) facilitated the phosphorylation of BSTA and its association with Akt1, and the BSTA-Akt1 interaction promoted the association of mTORC2 with Akt1 and phosphorylation of Akt1 at Ser⁴⁷³ in response to growth factor stimulation. Furthermore, analyses of bsta gene-trap murine embryonic stem cells revealed an essential function for BSTA and phosphorylation of Akt1 at Ser⁴⁷³ in promoting adipocyte differentiation, which required suppression of the expression of the gene encoding the transcription factor FoxC2. These findings indicate that BSTA is a molecular switch that promotes phosphorylation of Akt1 at Ser⁴⁷³ and reveal an mTORC2-BSTA-Akt1-FoxC2-mediated signaling mechanism that is critical for adipocyte differentiation.

Citation

Yixin Yao, Milind Suraokar, Bryant G Darnay, Brett G Hollier, Tattym E Shaiken, Takayuki Asano, Chien-Hung Chen, Benny H-J Chang, Yiling Lu, Gordon B Mills, Dos Sarbassov, Sendurai A Mani, James L Abbruzzese, Shrikanth A G Reddy. BSTA promotes mTORC2-mediated phosphorylation of Akt1 to suppress expression of FoxC2 and stimulate adipocyte differentiation. Science signaling. 2013 Jan 08;6(257):ra2