Endothelin-1 induces glut1 transcription through enhanced interaction between Sp1 and NF-kappaB transcription factors.

We have shown previously that endothelin-1 (ET-1) induction of Glut1 transcription is mediated by ET-1 responsive elements on enhancer 2, via both protein kinase Cepsilon (PKCepsilon)- and p42/p44 mitogen-activated protein kinase (MAPK)-dependent pathways. In the present study, we further explored the molecular mechanism involved. By using mutation constructs of luciferase reporter driven by Glut1 promoter/enhancers, chromatin immunoprecipitation and co-immunoprecipitation experiments, we were able to demonstrate that cooperative interaction between NF-kappaB and Sp1 were required to enhance Glut1 transcription in response to ET-1. While ET-1 may induce Sp1 expression via both PKC-and MAPK-dependent pathways, activation of NF-kappaB by ET-1 is mediated by a PKCepsilon/reactive oxygen species (ROS) cascade. Taken together, these results suggest that by activating NF-kappaB via PKCepsilon/ROS cascade and increasing Sp1 expression through both PKCepsilon- and MAPK-dependent pathways, ET-1 may activate Glut1 transcription by enhancing interaction between nuclear NF-kappaB and Sp1 as well as their binding to enhancer 2.