title: Insulin and chromium picolinate induce translocation of CD36 to the plasma membrane through different signaling pathways in 3T3-L1 adipocytes, and with a differential functionality of the CD36.
abstract: Chromium picolinate (CrPic) has been indicated to activate glucose transporter 4 (GLUT4) trafficking to the plasma membrane (PM) to enhance glucose uptake in 3T3-L1 adipocytes. In skeletal and heart muscle cells, insulin directs the intracellular trafficking of the fatty acid translocase/CD36 to induce the uptake of cellular long-chain fatty acid (LCFA). The current study describes the effects of CrPic and insulin on the translocation of CD36 from intracellular storage pools to the PM in 3T3-L1 adipocytes in comparison with that of GLUT4. Immunofluorescence microscopy and immunoblotting revealed that both CD36 and GLUT4 were expressed and primarily located intracellularly in 3T3-L1 adipocytes. Upon insulin or CrPic stimulation, PM expression of CD36 increased in a similar manner as that for GLUT4; the CrPic-stimulated PM expression was less strong than that of insulin. The increase in PM localization for these two proteins by insulin paralleled LCFA ([1-(14)C]palmitate) or [(3)H]deoxyglucose uptake in 3T3-L1 adipocytes. The induction of the PM expression of GLUT4, but not CD36, or substrate uptake by insulin and CrPic appears to be additive in adipocytes. Furthermore, wortmannin completely inhibited the insulin-stimulated translocation of GLUT4 or CD36 and prevented the increased uptake of glucose or LCFA in these cells. Taken together, for the first time, these findings suggest that both insulin and CrPic induce CD36 translocation to the PM in 3T3-L1 adipocytes and that their translocation-inducing effects are not additive. The signaling pathway inducing the translocations is different, apparently resulting in a differential activity of CD36.
authors: Department of Pharmacology, Shanghai Medical College, Fudan University, Shanghai 200032, China. 061101069@fudan.edu.cn
authors: Yiqun
authors: Y
authors: Wang
authors: Masja M
authors: MM
authors: Van Oort
authors: Minghui
authors: M
authors: Yao
authors: Dick J
authors: DJ
authors: Van der Horst
authors: Kees W
authors: KW
authors: Rodenburg
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D018955:CD36 Antigens / Q000378:metabolism*; D016466:CHO Cells; D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism*; D006224:Cricetinae; D003847:Deoxyglucose / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D015151:Immunoblotting; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D008856:Microscopy, Fluorescence; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism; D010848:Picolinic Acids / Q000494:pharmacology*; D021381:Protein Transport / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D018955:CD36 Antigens; D051275:Glucose Transporter Type 4; D007328:Insulin; D010848:Picolinic Acids; D003847:Deoxyglucose; D058539:Phosphatidylinositol 3-Kinase; C030614:picolinic acid