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Ang II‐Inducible PDGF‐D Transcription Requires Ser/Thr Residues In The Second Zinc Finger Region of Sp1: Novel Phosphospecific Antibodies Demonstrate that Sp1 is Phosphorylated by SMC Injury
Author(s) -
Khachigian Levon M,
Berndt Michael C,
Tan Nicole Y
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.471.6
Subject(s) - sp1 transcription factor , phosphorylation , zinc finger , microbiology and biotechnology , protein kinase c , biology , angiotensin ii , platelet derived growth factor receptor , transcription factor , promoter , chemistry , gene expression , gene , biochemistry , receptor , growth factor
Sp1, the first identified and cloned transcription factor, regulates gene expression via multiple mechanisms including direct protein‐DNA interactions, protein‐protein interactions, chromatin remodelling and maintenance of methylation‐free CpG islands. Sp1 is itself regulated at different levels, for example, by glycosylation, acetylation and phosphorylation by kinases such as the atypical protein kinase C‐zeta. Although Sp1 controls the basal and inducible regulation of many genes, the post‐translational processes regulating its function and their relevance to pathology are not well understood. Here we have used a variety of approaches to identify 3 amino acids (Thr668, Ser670 and Thr681) in the zinc finger (ZNF) domain of Sp1 that are modified by PKC‐zeta, and have generated novel anti‐peptide antibodies recognising the PKC‐zeta‐phosphorylated form of Sp1. Angiotensin II (Ang II), which activates PKC‐zeta phosphorylation (at Thr410) via the Ang II Type I receptor, stimulates Sp1 phosphorylation and increases Sp1 binding to the PDGF‐D promoter. All 3 residues in Sp1 (Thr668, Ser670 and Thr681) are required for Sp1‐dependent PDGF‐D activation in response to Ang II. Immunohistochemical analysis revealed that phosphorylated Sp1 is expressed in SMCs of human atherosclerotic plaques, and is dynamically expressed together with PDGF‐D in SMCs of the injured rat carotid artery wall. This study provides new insights into the regulatory mechanisms controlling the PKC‐zeta‐phospho‐Sp1 axis and Ang II‐inducible gene expression.