Identification of a proline-rich Akt substrate as a 14-3-3 binding partner

Area of Science:

• Molecular Biology
• Cell Signaling
• Biochemistry

Background:

• Akt (protein kinase B) is a key downstream effector of the phosphatidylinositol 3-kinase pathway.
• Akt plays critical roles in insulin signaling, cell growth, apoptosis inhibition, and cell transformation.
• The full range of Akt substrates and their functions are not completely understood.

Purpose of the Study:

• To identify and characterize novel substrates of Akt.
• To investigate the role of PRAS40 as a potential Akt substrate.
• To elucidate the relationship between Akt phosphorylation, PRAS40, and 14-3-3 binding.

Main Methods:

• Utilized 14-3-3 binding assays and antibodies recognizing Akt phosphorylation consensus sites.
• Performed in vitro phosphorylation assays with purified Akt and PRAS40.
• Investigated PRAS40 phosphorylation in cells with inducible Akt activation and in Akt1/Akt2 knockout cells.

Main Results:

• Identified a 40-kDa proline-rich protein, PRAS40, as a major Akt substrate.
• Demonstrated that Akt directly phosphorylates PRAS40 at a site consistent with in vivo phosphorylation.
• Showed that Akt activation is sufficient to induce PRAS40 phosphorylation, and Akt-deficient cells have reduced PRAS40 phosphorylation.
• Confirmed that PRAS40 phosphorylation by Akt results in its binding to 14-3-3 proteins.

Conclusions:

• PRAS40 is a novel substrate of Akt.
• Akt-mediated phosphorylation of PRAS40 is a key event regulating its interaction with 14-3-3 proteins.
• This discovery provides new insights into the Akt signaling pathway and its downstream effectors.