Synapses of amphids defective (SAD-A) kinase promotes glucose-stimulated insulin secretion through activation of p21-activated kinase (PAK1) in pancreatic beta-Cells.
Article Details
- CitationCopy to clipboard
Nie J, Sun C, Faruque O, Ye G, Li J, Liang Q, Chang Z, Yang W, Han X, Shi Y
Synapses of amphids defective (SAD-A) kinase promotes glucose-stimulated insulin secretion through activation of p21-activated kinase (PAK1) in pancreatic beta-Cells.
J Biol Chem. 2012 Jul 27;287(31):26435-44. doi: 10.1074/jbc.M112.378372. Epub 2012 Jun 5.
- PubMed ID
- 22669945 [ View in PubMed]
- Abstract
The p21-activated kinase-1 (PAK1) is implicated in regulation of insulin exocytosis as an effector of Rho GTPases. PAK1 is activated by the onset of glucose-stimulated insulin secretion (GSIS) through phosphorylation of Thr-423, a major activation site by Cdc42 and Rac1. However, the kinase(s) that phosphorylates PAK1 at Thr-423 in islet beta-cells remains elusive. The present studies identified SAD-A (synapses of amphids defective), a member of AMP-activated protein kinase-related kinases exclusively expressed in brain and pancreas, as a key regulator of GSIS through activation of PAK1. We show that SAD-A directly binds to PAK1 through its kinase domain. The interaction is mediated by the p21-binding domain (PBD) of PAK1 and requires both kinases in an active conformation. The binding leads to direct phosphorylation of PAK1 at Thr-423 by SAD-A, triggering the onset of GSIS from islet beta-cells. Consequently, ablation of PAK1 kinase activity or depletion of PAK1 expression completely abolishes the potentiating effect of SAD-A on GSIS. Consistent with its role in regulating GSIS, overexpression of SAD-A in MIN6 islet beta-cells significantly stimulated cytoskeletal remodeling, which is required for insulin exocytosis. Together, the present studies identified a critical role of SAD-A in the activation of PAK1 during the onset of insulin exocytosis.