Dioleoylphosphoethanolamine Retains Cell Surface GLUT4 by Inhibiting PKCα-Driven Internalization

Abstract

Background/aims: Phosphatidylethanolamine, a component of the plasma membrane, regulates diverse cellular processes. The present study investigated the role of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) in the trafficking of the glucose transporter GLUT4 and the glucose homeostasis.

Methods: Monitoring of GLUT4 trafficking, GLUT4 internalization assay, and glucose uptake assay were carried out using differentiated 3T3-L1-GLUT4myc adipocytes. Akt1/2 and PKC isozymes were knocked-down by transfecting each siRNA. Cell-free PKC assay and in situ PKCα assay with a FRET probe were carried out. Oral glucose tolerance test (OGTT) was performed using BKS.Cg-+Lepdb/+Lebdb/Jcl mice, an animal model of type 2 diabetes mellitus (DM).

Results: DOPE increased cell surface localization of the glucose transporter GLUT4 in differentiated 3T3-L1-GLUT4myc adipocytes, regardless of Akt activation. Likewise, PKCα deficiency increased cell surface localization of GLUT4, that occludes the effect of DOPE. DOPE clearly suppressed phorbol 12-myristate 13-acetate-induced PKCα activation in the cell-free and in situ PKC assay. DOPE and PKCα deficiency cancelled endocytic internalization of GLUT4 localized on the plasma membrane after insulin stimulation. DOPE significantly enhanced glucose uptake into cells. A similar effect was obtained by knocking-down PKCα, that occludes the effect of DOPE. In OGTT, oral administration with DOPE effectively restricted an increase in the blood glucose levels after glucose loading in type 2 DM model mice.

Conclusion: The results of the present study show that DOPE retains cell surface GLUT4 by suppressing PKCα-driven endocytic internalization of GLUT4, to enhance glucose uptake into cells and restrict an increase in the blood glucose levels after glucose loading in type 2 DM.

Keywords: Dioleoylphosphatidylethanolamine; Endocytic internalization; GLUT4; Glucose uptake; PKCα.