Retinoic acid utilizes CREB and USF1 in a transcriptional feed-forward loop in order to stimulate MKP1 expression in human immunodeficiency virus-infected podocytes

Authors:
Lu TC, Wang Z, Feng X, Chuang P, Fang W, Chen Y, Neves S, Maayan A, Xiong H, Liu Y, Iyengar R, Klotman PE, He JC
In:
Source: Mol Cell Biol
Publication Date: (2008)
Issue: 28(18): 5785-94
Research Area:
Cancer Research/Cell Biology
Cells used in publication:
Podocyte, mouse
Species: mouse
Tissue Origin: kidney
Platform:
Nucleofector® I/II/2b
Abstract
Nef induced podocyte proliferation and dedifferentiation via MAPK1,2 activation plays a role in HIV nephropathy pathogenesis. All-trans retinoic acid (atRA) reverses the HIV-induced podocyte phenotype by activating cAMP/PKA and inhibiting MAPK1,2. Here we show that atRA, through cAMP and PKA, triggers a feed-forward loop involving CREB and USF1 to induce biphasic stimulation of MKP1. AtRA stimulated CREB and USF1 binding to the MKP1 gene promoter as shown by gel shifting and Chromatin immunoprecipitation assays. CREB directly mediated the early phase of atRA-induced MKP1 stimulation; whereas the later phase was mediated by CREB indirectly through induction of USF1. These findings were confirmed by reporter gene assay using MKP1 promoter with mutation of CRE or Ebox binding sites. Consistent with these findings, the biological effects of atRA on podocytes were inhibited by silencing either MKP1, CREB, or USF1 with siRNA. AtRA also induced CREB phosphorylation, MKP1 expression, and reduced MAPK1,2 phosphorylation in kidneys of HIV-1 transgenic mice. We conclude that atRA induces sustained activation of MKP1 to suppress Nef-induced activation of Src-MAPK1,2 pathway, thus returning the podocyte to a more differentiated state. The mechanism involves a feed-forward loop where activation of one TF (CREB) leads to induction of a second TF (USF1).