title: Krüppel-like factor 4 (KLF4/GKLF) is a target of bone morphogenetic proteins and transforming growth factor beta 1 in the regulation of vascular smooth muscle cell phenotype.
abstract: Vascular smooth muscle cell (VSMC) differentiation and phenotypic modulation is characterized by changes in mRNA expression for smooth muscle (SM) marker contractile proteins such as alpha-SM actin and SM22 alpha. Transforming growth factor beta1 (TGF-beta 1) is a potent VSMC differentiation factor; however, it is not known if other TGF-beta-superfamily members, in particular the bone morphogenetic proteins (BMPs), modulate VSMC phenotype. Here we demonstrate that a large subset of TGF-beta-superfamily members and their type I receptors are differentially co-expressed as VSMC phenotype changes during fetal/neonatal development and that BMP2, -4, and -6 reciprocally regulate SM-marker mRNA and protein expression in vitro. BMP2 and BMP6 decrease expression of the SM markers alpha-SM actin, SM22alpha, and calponin in rat VSMCs, whereas BMP4 increases their expression. The effects of BMP-2, -4, and -6 on SM marker gene transcription are mediated through a consensus TGF-beta-controlling element, the TCE, which is common to regulatory regions of SM-marker genes. Moreover, co-treatment experiments revealed that BMP-2, -4, and -6 each inhibit TGF-beta 1-modulated increases in SM22alpha reporter gene activity. Regardless of whether they positively or negatively regulate SM marker expression, TGF-beta 1 and BMP-2, -4, and -6 all induced binding of the Krüppel-like transcription factor, GKLF/KLF4, to the TGF-beta control element. Induction of KLF4 was confirmed by immunocytochemistry and Western blotting, which revealed that a lower molecular weight KLF4 protein is induced after treatment with TGF-beta-superfamily members. Taken together, our results demonstrate that multiple members of the TGF-beta superfamily act in concert to modulate VSMC phenotype.
authors.affiliation: University of Cambridge, Department of Medicine, Addenbrooke's Centre for Clinical Investigation Level 6, Box 110 Addenbrooke's Hospital, Hills Rd., Cambridge CB2 2QQ, United Kingdom.
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: King
authors.forename: Valentine P
authors.initials: VP
authors.lastname: Iyemere
authors.forename: Peter L
authors.initials: PL
authors.lastname: Weissberg
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Shanahan
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism*; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D010641:Phenotype; D051381:Rats; D011921:Rats, Inbred WKY; D014157:Transcription Factors / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D000199:Actins; D019485:Bone Morphogenetic Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; C000715469:Klf4 protein, rat; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D014157:Transcription Factors; D016212:Transforming Growth Factor beta