Calpain facilitates GLUT4 vesicle translocation during insulin-stimulated glucose uptake in adipocytes.
Calpains are a family of non-lysosomal cysteine proteases. Recent studies have identified a member of the calpain family of proteases, calpain 10, as a putative diabetes-susceptibility gene that may be involved in the development of type 2 diabetes. Inhibition of calpain activity has been shown to reduce insulin-stimulated glucose uptake in isolated rat-muscle strips and adipocytes. In this report, we examine the mechanism by which calpain affects insulin-stimulated glucose uptake in 3T3-L1 adipocytes. Inhibition of calpain activity resulted in approx. a 60% decrease in insulin-stimulated glucose uptake. Furthermore, inhibition of calpain activity prevented the translocation of insulin-responsive glucose transporter 4 (GLUT4) vesicles to the plasma membrane, as demonstrated by fluorescent microscopy of whole cells and isolated plasma membranes; it did not, however, alter the total GLUT4 protein content. While inhibition of calpain did not affect the insulin-mediated proximal steps of the phosphoinositide 3-kinase pathway, it did prevent the insulin-stimulated cortical actin reorganization required for GLUT4 translocation. Specific inhibition of calpain 10 by antisense expression reduced insulin-stimulated GLUT4 translocation and actin reorganization. Based on these findings, we propose a role for calpain in the actin reorganization required for insulin-stimulated GLUT4 translocation to the plasma membrane in 3T3-L1 adipocytes. These studies identify calpain as a novel factor involved in GLUT4 vesicle trafficking and suggest a link between calpain activity and the development of type 2 diabetes.
Paul
David S
DS
Department of Nutrition, University of North Carolina School of Public Health, 2216A McGavran-Greenberg, Chapel Hill, NC 27599, USA.
Harmon
Anne W
AW
Winston
Courtney P
CP
Patel
Yashomati M
YM
D008841:Actin Cytoskeleton / Q000648:ultrastructure; D017667:Adipocytes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002154:Calpain / Q000037:antagonists & inhibitors / Q000502:physiology*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000494:pharmacology*; D007976:Leupeptins / Q000494:pharmacology; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D010766:Phosphorylation; D021381:Protein Transport / Q000187:drug effects; D015398:Signal Transduction; D022161:Transport Vesicles / Q000378:metabolism*
D015853:Cysteine Proteinase Inhibitors; D051275:Glucose Transporter Type 4; D007328:Insulin; D007976:Leupeptins; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C063261:acetylleucyl-leucyl-norleucinal; D002154:Calpain; C415197:calpain 10; D005947:Glucose