| First Author | Xu Y | Year | 2016 |
| Journal | J Cell Sci | Volume | 129 |
| Issue | 10 | Pages | 2085-95 |
| PubMed ID | 27076519 | Mgi Jnum | J:246198 |
| Mgi Id | MGI:5924420 | Doi | 10.1242/jcs.174805 |
| Citation | Xu Y, et al. (2016) Optogenetic activation reveals distinct roles of PIP3 and Akt in adipocyte insulin action. J Cell Sci 129(10):2085-95 |
| abstractText | Glucose transporter 4 (GLUT4; also known as SLC2A4) resides on intracellular vesicles in muscle and adipose cells, and translocates to the plasma membrane in response to insulin. The phosphoinositide 3-kinase (PI3K)-Akt signaling pathway plays a major role in GLUT4 translocation; however, a challenge has been to unravel the potentially distinct contributions of PI3K and Akt (of which there are three isoforms, Akt1-Akt3) to overall insulin action. Here, we describe new optogenetic tools based on CRY2 and the N-terminus of CIB1 (CIBN). We used these 'Opto' modules to activate PI3K and Akt selectively in time and space in 3T3-L1 adipocytes. We validated these tools using biochemical assays and performed live-cell kinetic analyses of IRAP-pHluorin translocation (IRAP is also known as LNPEP and acts as a surrogate marker for GLUT4 here). Strikingly, Opto-PIP3 largely mimicked the maximal effects of insulin stimulation, whereas Opto-Akt only partially triggered translocation. Conversely, drug-mediated inhibition of Akt only partially dampened the translocation response of Opto-PIP3 In spatial optogenetic studies, focal targeting of Akt to a region of the cell marked the sites where IRAP-pHluorin vesicles fused, supporting the idea that local Akt-mediated signaling regulates exocytosis. Taken together, these results indicate that PI3K and Akt play distinct roles, and that PI3K stimulates Akt-independent pathways that are important for GLUT4 translocation. |
