Regulation of GLUT1‐mediated glucose and dehydroascorbic acid (DHA) transport

Abstract

The GLUT1 PDZ‐binding motif that plays a role in GLUT1 localization contains a reported phosphorylation site, S490, for ataxia telangiectasia mutated (ATM). The objective of this study is to determine whether ATM and/or modification of GLUT1 S490 affect GLUT1 localization, trafficking, and transport activity. Mouse extensor digitorum longus (EDL) muscles were excised from wild type and ATM −/− mice and then subjected to a DHA transport assay. ATM inhibition by KU55933 or CP466722 or ATM dysfunction (ATM−/−) in EDL resulted in reduced DHA transport (~30–65%, p<0.05). Also, L6 myoblasts were transfected with FLAG tagged GLUT1 (FLAG‐GLUT1) or FLAG‐GLUT1 S490A and S490D site mutants. ATM inhibition significantly diminished cell surface FLAG‐GLUT1 (~20–80%, p<0.05) and glucose transport in L6 myotubes (~50%, p<0.05) with a concomitant reduction in GLUT1 externalization (~20%, p<0.05). The S490D mutation increased cell surface GLUT1 (~35%, p<0.05) as well as GLUT1‐mediated glucose transport (~2‐fold, p<0.05), while S490A had opposite effects. These results provide evidence that ATM and GLUT1 S490 mutations affect cell surface GLUT1 and GLUT1‐mediated transport. Supported by USPHS award 1R15DK091904.