Effects of AMPK activators on the sub-cellular distribution of fatty acid transporters CD36 and FABPpm

Abstract

In heart and skeletal muscle, enhanced contractile activity induces an increase in the uptake of glucose and long-chain fatty acids (LCFA) via an AMP-activated protein kinase (AMPK)-regulated mechanism. AMPK activation induces glucose uptake through translocation of glucose transporter 4 (GLUT4) from intracellular pools to the plasma membrane (PM). AMPK-mediated LCFA uptake has been suggested to be regulated by a similar translocation of the LCFA transporters CD36 and plasma membrane-associated fatty acid binding protein (FABPpm). In contrast to the well-characterized GLUT4 translocation, documentation of the proposed translocation of both LCFA transporters is rudimentary. Therefore, we adopted a cell culture system to investigate the localization of CD36 and FABPpm compared with GLUT4, in the absence and presence of AMPK activators oligomycin and AICAR. To this end, intact Chinese hamster ovary (CHO) cells stably expressing CD36 or myc-tagged GLUT4 (GLUT4myc) were used; FABPpm is endogenously expressed in CHO cells. Immuno-fluorescence microscopy revealed that CD36 PM localization resembled that of GLUT4, while FABPpm localized to other PM domains. Upon stimulation with oligomycin or AICAR, CD36 translocated (1.5-fold increase) to a PM location similar to that of GLUT4myc. In contrast, the PM FABPpm content did not change upon AMPK activation. Thus, for the first time in intact cells, we present evidence for AMPK-mediated translocation of CD36 from intracellular pools to the PM, similar to GLUT4, whereas FABPpm is not relocated.