Extracellular glucose level regulates dependence on 78 for cell surface localization of multipass transmembrane proteins in HeLa cells

Abstract

Many human-cultured cell lines survive glucose starvation, but the underlying mechanisms remain unclear. Here, we searched for proteins required for cellular adaptation to glucose-limited conditions and identified several endoplasmic reticulum chaperones in the glucose-regulated protein (GRP) family as proteins enriched in the cellular membrane. Surprisingly, these proteins, which are required for cell surface localization of GLUT1 under high-glucose conditions, become dispensable for targeting GLUT1 to the surface upon glucose starvation. In marked contrast, cell surface localization of single-pass transmembrane proteins, such as epidermal growth factor receptor and CD98, is not disturbed by GRP78 depletion regardless of the extracellular glucose level. These results indicate that the extracellular glucose level regulates dependence on the GRPs for cell surface localization of multipass transmembrane proteins.