Inhibition of Protein Kinase CβII Increases Glucose Uptake in 3T3-L1 Adipocytes through Elevated Expression of Glucose Transporter 1 at the Plasma Membrane

• Published in: Molecular endocrinology (Baltimore, Md.) Md.), 2003-07, Vol.17 (7), p.1230-1239
• Main Authors: Bosch, Remko R, Bazuine, Merlijn, Wake, Michelle M, Span, Paul N, Olthaar, André J, Schürmann, Annette, Maassen, J. Antonie, Hermus, Ad R. M. M, Willems, Peter H. G. M, Sweep, C. G. J. (FRED)
• Format: Article
• Language: English
• ISSN: 0888-8809; 1944-9917
• DOI: 10.1210/me.2003-0057

The mechanism via which diacylglycerol-sensitive protein kinase Cs (PKCs) stimulate glucose transport in insulin-sensitive tissues is poorly defined. Phorbol esters, such as phorbol-12-myristate-13-acetate (PMA), are potent activators of conventional and novel PKCs. Addition of PMA increases the rate of glucose uptake in many different cell systems. We attempted to investigate the mechanism via which PMA stimulates glucose transport in 3T3-L1 adipocytes in more detail. We observed a good correlation between the rate of disappearance of PKCβII during prolonged PMA treatment and the increase in glucose uptake. Moreover, inhibition of PKCβII with a specific myristoylated PKCβC2–4 peptide inhibitor significantly increased the rate of glucose transport. Western blot analysis demonstrated that both PMA treatment and incubation with the myristoylated PKCβC2–4 pseudosubstrate resulted in more glucose transporter (GLUT)-1 but not GLUT-4 at the plasma membrane. To our knowledge, we are the first to demonstrate that inactivation of PKC, most likely PKCβII, elevates glucose uptake in 3T3-L1 adipocytes. The observation that PKCβII influences the rate of glucose uptake through manipulation of GLUT-1 expression levels at the plasma membrane might reveal a yet unidentified regulatory mechanism involved in glucose homeostasis.