title: Lipid rafts are required for signal transduction by angiotensin II receptor type 1 in neonatal glomerular mesangial cells.
abstract: Angiotensin II (ANG-II) receptors (AGTRs) contribute to renal physiology and pathophysiology, but the underlying mechanisms that regulate AGTR function in glomerular mesangium are poorly understood. Here, we show that AGTR1 is the functional AGTR subtype expressed in neonatal pig glomerular mesangial cells (GMCs). Cyclodextrin (CDX)-mediated cholesterol depletion attenuated cell surface AGTR1 protein expression and ANG-II-induced intracellular Ca(2+) ([Ca(2+)]i) elevation in the cells. The COOH-terminus of porcine AGTR1 contains a caveolin (CAV)-binding motif. However, neonatal GMCs express CAV-1, but not CAV-2 and CAV-3. Colocalization and in situ proximity ligation assay detected an association between endogenous AGTR1 and CAV-1 in the cells. A synthetic peptide corresponding to the CAV-1 scaffolding domain (CSD) sequence also reduced ANG-II-induced [Ca(2+)]i elevation in the cells. Real-time imaging of cell growth revealed that ANG-II stimulates neonatal GMC proliferation. ANG-II-induced GMC growth was attenuated by EMD 66684, an AGTR1 antagonist; BAPTA, a [Ca(2+)]i chelator; KN-93, a Ca(2+)/calmodulin-dependent protein kinase II inhibitor; CDX; and a CSD peptide, but not PD 123319, a selective AGTR2 antagonist. Collectively, our data demonstrate [Ca(2+)]i-dependent proliferative effect of ANG-II and highlight a critical role for lipid raft microdomains in AGTR1-mediated signal transduction in neonatal GMCs.
authors.affiliation: Department of Physiology, College of Medicine, University of Tennessee Health Science Center, 894 Union Avenue, Memphis, TN 38163 , USA. Electronic address: aadebiyi@uthsc.edu.
authors.forename: Adebowale
authors.initials: A
authors.lastname: Adebiyi
authors.affiliation: Department of Physiology, College of Medicine, University of Tennessee Health Science Center, 894 Union Avenue, Memphis, TN 38163 , USA.
authors.forename: Hitesh
authors.initials: H
authors.lastname: Soni
authors.affiliation: Department of Physiology, College of Medicine, University of Tennessee Health Science Center, 894 Union Avenue, Memphis, TN 38163 , USA.
authors.forename: Theresa A
authors.initials: TA
authors.lastname: John
authors.affiliation: Department of Physiology, College of Medicine, University of Tennessee Health Science Center, 894 Union Avenue, Memphis, TN 38163 , USA.
authors.forename: Fen
authors.initials: F
authors.lastname: Yang
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D018507:Gene Expression Regulation, Developmental; D008297:Male; D021962:Membrane Microdomains / Q000502:physiology*; D050527:Mesangial Cells / Q000378:metabolism* / Q000648:ultrastructure; D061251:Primary Cell Culture; D044140:Receptor, Angiotensin, Type 1 / Q000502:physiology*; D015398:Signal Transduction; D013552:Swine
chemical_list: D044140:Receptor, Angiotensin, Type 1; D002118:Calcium
keywords: Angiotensin II; Caveolin-1 scaffolding domain; Glomerular mesangial cells; Intracellular calcium; Lipid rafts; Proliferation