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Cloning and expression of a rat Smad1: Regulation by TGFß and modulation by the ras/MEK pathway
Author(s) -
Yue Jianbo,
Hartsough Melanie T.,
Frey Randall S.,
Frielle Thomas,
Mulder Kathleen M.
Publication year - 1999
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/(sici)1097-4652(199903)178:3<387::aid-jcp13>3.0.co;2-8
Subject(s) - r smad , biology , phosphorylation , smad2 protein , signal transduction , microbiology and biotechnology , transforming growth factor , bone morphogenetic protein , mutant , kinase , mapk/erk pathway , receptor , cell culture , endogeny , smad , gene , biochemistry , growth factor , genetics , tgf alpha
A new family of signaling intermediates for TGFß superfamily members and other growth factors has recently been identified and termed Smads. It has been suggested that the Smad1 subfamily is regulated primarily by the TGFß superfamily member bone morphogenetic protein (BMP). Here we demonstrate that TGFß induced phosphorylation of endogenous Smad1 in untransformed IECs and that the RI and RII TGFß receptors were detectable in Smad1 immunocomplexes. Expression of a dominant‐negative mutant of Ras inhibited the ability of TGFß to phosphorylate endogenous Smad1. In a separate series of experiments, we have cloned a rat homologue of the drosophila mad gene (termed RSmad1) by screening an intestinal epithelial cell (IEC) cDNA library. By using an in vitro kinase assay with RSmad1 as the substrate, we demonstrate that the TGFß receptor complex can directly phosphorylate RSmad1. We show, further, that a dominant‐negative mutant of MEK1 inhibited the ability of RSmad1 to induce the TGFß‐responsive reporter p3TP‐Lux in a human breast cancer cell line. Collectively, our data demonstrate that TGFß can regulate Smad1 and that the Ras and MEK signaling components are partially required for the ability of TGFß to regulate Smad1. J. Cell. Physiol. 178:387–396, 1999. © 1999 Wiley‐Liss, Inc.