title: Differential phosphorylation of calreticulin affects AT1 receptor mRNA stability in VSMC.
abstract: The AT1 receptor plays a pivotal role for the pathogenesis of hypertension and atherosclerosis. AT1 receptor expression is regulated posttranscriptionally via destabilization of the AT1 receptor mRNA by mRNA binding proteins. Recently, we identified calreticulin as a novel binding protein within the 3'untranslated region of the AT1 receptor mRNA. Calreticulin phosphorylation is essential for binding of the AT1 receptor mRNA. In crosslink experiments, we identified src kinase as the key enzyme for calreticulin phosphorylation. Overexpression of src sense DNA resulted in vascular smooth muscle cells (VSMC) in destabilization, overexpression of src antisense resulted in stabilisation of the AT1 receptor mRNA. Furthermore, phosphorylation/dephosphorylation sites of calreticulin and their impact on the AT1 receptor mRNA stability were investigated. VSMC were stimulated with AngII before tyrosine phosphorylation as well as serine phosphorylation of calreticulin were analysed via immunoprecipitation. Stimulation of VSMC with AngII resulted in enhanced tyrosine and reduced serine phosphorylation. Both effects are essential for AT1 mRNA stability as assessed by use of pharmacological inhibitors of serine dephosphorylation (cantharidin/ocadaic acid) or tyrosine phosphorylation (tyrphostin/orthovanadat). These findings imply an important role of serine dephosphorylation and tyrosine phosphorylation on calreticulin mediated AT1 receptor mRNA stability.
authors.affiliation: Medizinische Klinik und Poliklinik II, Innere Medizin, Universitätsklinikum Bonn, Sigmund Freud Strasse 25, 53105 Bonn, Germany. cornelius.mueller@ukb.uni-bonn.de
authors.forename: Cornelius F H
authors.initials: CF
authors.lastname: Mueller
authors.forename: Kerstin
authors.initials: K
authors.lastname: Wassmann
authors.forename: Anja
authors.initials: A
authors.lastname: Berger
authors.forename: Stefan
authors.initials: S
authors.lastname: Holz
authors.forename: Sven
authors.initials: S
authors.lastname: Wassmann
authors.forename: Georg
authors.initials: G
authors.lastname: Nickenig
mesh_terms: D020413:3' Untranslated Regions / Q000378:metabolism; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D037282:Calreticulin / Q000378:metabolism*; D002193:Cantharidin / Q000494:pharmacology; D002478:Cells, Cultured; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D020871:RNA Stability; D051381:Rats; D044140:Receptor, Angiotensin, Type 1 / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D020413:3' Untranslated Regions; D037282:Calreticulin; D047428:Protein Kinase Inhibitors; D044140:Receptor, Angiotensin, Type 1; D000804:Angiotensin II; D014443:Tyrosine; D012694:Serine; D019061:src-Family Kinases; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D002193:Cantharidin