Endothelin-1 induction of Glut1 transcription in 3T3-L1 adipocytes involves distinct PKCε- and p42/p44 MAPK-dependent pathways

We have shown previously that chronic exposure to endothelin-1 (ET-1) may stimulate GLUT1-mediated glucose transport in 3T3-L1 adipocytes via both protein kinase C (PKC)- and mitogen-activated protein kinase (p42/p44 MAPK)-dependent pathways. In the present study, by using a luciferase reporter driven by Glut1 promoter and enhancers (pLuc-GT1/E1/E2) and various constitutively active and dominant negative mutants of PKC isoforms, we identified PKCε as the PKC isoform involved. In addition, we provide evidence that there is no direct interaction between ET-1 activated PKCε and MAPK, at least at the kinase activity level. Furthermore, investigations employing deletion mutants of pLuc-GT1/E1/E2 to locate the putative ET-1 responsive sites and inhibitory agents to suppress the activities of putative transcription factors suggested that transcription factors CREB, Sp1 and NF-κB were involved. In summary, the results of this study indicate that ET-1 induction of Glut1 transcription involves distinct PKCε- and MAPK-dependent pathways, as well as downstream transcription factors CREB, Sp1 and NF-κB.