Cell adhesion molecule IGPR-1 activates AMPK connecting cell adhesion to energy sensing and autophagy

Abstract

Immunoglobulin (Ig) and proline-rich receptor-1 (IGPR-1) is a cell adhesion molecule that regulates angiogenesis and endothelial barrier function. IGPR-1 is activated by shear stress and mediates endothelial cells response to shear stress. Autophagy plays critical roles in the maintenance of endothelial cells in response to cellular stress caused by blood flow. However, whether IGPR-1 is activated in response to, and mediates autophagy remains unknown. In this study, we demonstrate that IGPR-1 is activated by autophagy inducing stimuli, such as amino acid starvation, nutrient deprivation, rapamycin and lipopolysaccharide (LPS). We have identified I{kappa}B kinase{beta} (IKK{beta}) as a key serine/threonine kinase activated by autophagy stimuli and mediates phosphorylation of IGPR-1 at Ser220. Activation of IGPR-1, in turn, stimulates phosphorylation of AMP-activated protein kinase (AMPK), which leads to phosphorylation of key pro-autophagy proteins, ULK1 and Beclin-1 (BECN1), increased LC3-II levels and accumulation of LC3 punctum. This study demonstrates that IGPR-1 is activated by and regulates autophagy, connecting cell adhesion to autophagy, a finding that has important significance for autophagy-driven pathologies such cardiovascular diseases and cancer.