GLUT-4 degradation rate: reduction in rat adipocytes in fasting and streptozotocin-induced diabetes.
With the use of [3H]leucine pulse-chase and immunoprecipitation methods, we measured the rate of GLUT-4 degradation in rat adipocytes in the steady state at 37 degrees C. We also studied the relationship of the reduced GLUT-4 levels observed in fasted and streptozotocin (STZ)-induced diabetic rats on degradation. GLUT-4 degradation was a simple, first-order decay process. The decay was describable by a single, first-order rate constant (k). A k value of 0.061/h was estimated in control rat adipocytes. In the adipocytes of fasted and STZ-induced diabetic rats, cellular GLUT-4 contents were reduced to 36 and 43% of the control, respectively. The rates of GLUT-4 degradation were also reduced significantly, with kappa values of 0.038 and 0.041/h, respectively. These changes were reversible; the decreased values returned to control values when GLUT-4 contents were normalized by refeeding and insulin injection. These findings demonstrate the presence of a posttranslational mechanism in rat adipocytes that reduces the GLUT-4 degradation rate constant when the cellular GLUT-4 level is reduced by a pretranslational defect.
Kim
S S
SS
Biophysical Laboratory, Veterans Administration Medical Center, Buffalo, New York.
Bae
J W
JW
Jung
C Y
CY
D017667:Adipocytes / Q000378:metabolism*; D000821:Animal Feed; D000818:Animals; D002469:Cell Separation; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D005215:Fasting; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000494:pharmacology; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values
D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495694:Slc2a4 protein, rat