title: Angiotensin II stimulates fibronectin protein synthesis via a Gβγ/arachidonic acid-dependent pathway.
abstract: In rabbit proximal tubular cells, ANG II type 2-receptor (AT2)-induced arachidonic acid release is PLA2 coupled and dependent of G protein βγ (Gβγ) subunits. Moreover, ANG II activates ERK1/2 and transactivates EGFR via a c-Src-dependent mechanism. Arachidonic acid has been shown to mimic this effect, at least in part, by an undetermined mechanism. In this study, we determined the effects of ANG II on fibronectin expression in cultured rabbit proximal tubule cells and elucidated the signaling pathways associated with such expression. We found that ANG II and transfection of Gβγ subunits directly increased fibronectin protein expression, and this increase was inhibited by overexpression of β-adrenergic receptor kinase (βARK)-ct or DN-Src. Moreover, ANG II-induced fibronectin protein expression was significantly abrogated by the AT2 receptor antagonist PD123319. In addition, inhibition of cystolic PLA2 diminished ANG II-induced fibronectin expression. Endogenous arachidonic acid mimicked ANG II-induced fibronectin expression. We also found that overexpression of Gβγ subunits induced c-Src, ERK1/2, and EGFR tyrosine phosphorylation, which can be inhibited by overexpression of βARK-ct or DN-Src. Gβγ also induced c-Src SH2 domain association with the EGFR. Supporting these findings, in rabbit proximal tubular epithelium, immunoblot analysis indicated that βγ expression was significant. Interestingly, arachidonic acid- and eicosatetraenoic acid-induced responses were preserved in the presence of βARK-ct. This is the first report demonstrating the regulation of EGFR, ERK1/2, c-Src, and fibronectin by Gβγ subunits in renal epithelial cells. Moreover, this work demonstrates a role for Gβγ heterotrimeric proteins in ANG II, but not arachidonic acid, signaling in renal epithelial cells.
authors.affiliation: Department of Physiology, Arizona College of Osteopathic Medicine, Midwestern University, Glendale, Arizona; and lalexa@midwestern.edu.
authors.forename: Larry D
authors.initials: LD
authors.lastname: Alexander
authors.affiliation: Division of Nephrology and Hypertension, Department of Medicine, Case Western Reserve University School of Medicine and University Hospitals of Cleveland, Cleveland, Ohio.
authors.forename: Yaxian
authors.initials: Y
authors.lastname: Ding
authors.affiliation: Division of Nephrology and Hypertension, Department of Medicine, Case Western Reserve University School of Medicine and University Hospitals of Cleveland, Cleveland, Ohio.
authors.forename: Suganthi
authors.initials: S
authors.lastname: Alagarsamy
authors.affiliation: Division of Nephrology and Hypertension, Department of Medicine, Case Western Reserve University School of Medicine and University Hospitals of Cleveland, Cleveland, Ohio.
authors.forename: Xiaolan
authors.initials: X
authors.lastname: Cui
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D000081247:CSK Tyrosine-Protein Kinase; D002478:Cells, Cultured; D066246:ErbB Receptors / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism*; D044387:GTP-Binding Protein beta Subunits / Q000378:metabolism*; D044388:GTP-Binding Protein gamma Subunits / Q000378:metabolism*; D007093:Imidazoles / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008297:Male; D023421:Models, Animal; D011725:Pyridines / Q000494:pharmacology; D011817:Rabbits; D044139:Receptor, Angiotensin, Type 2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D005353:Fibronectins; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D007093:Imidazoles; D011725:Pyridines; D044139:Receptor, Angiotensin, Type 2; D000804:Angiotensin II; C073402:PD 123319; D016718:Arachidonic Acid; D066246:ErbB Receptors; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases
keywords: Gβγ; angiotensin II; arachidonic acid; c-Src, epidermal growth factor receptor transactivation; carboxyl terminus of β-adrenergic receptor kinase-1; mitogen-activated protein kinase