Overexpression of aminopeptidase A abolishes the growth promoting effects of angiotensin II in cultured mouse mesangial cells.
Angiotensin II (Ang II) has diverse effects on the glomerular tuft such as regulation of glomerular hemodynamics and stimulation of mesangial cell growth, and may be one pivotal factor in the progression of renal disease. In order to locally inactivate Ang II, we overexpressed aminopeptidase A (E.C. 3.4.11.7; ATA), a peptidase involved in the conversion of Ang II into angiotensin III, in a mouse mesangial cell line (MMC) that normally does not exhibit this enzyme. Stable transfections were selected in medium containing G418. ATA-overexpressing clones ATA5 and ATA21 revealed mRNA, protein, and enzyme activity in contrast to wild-type MMCs or mock-transfected Neo3 cells (stably transfected with expression vectors without ATA cDNA). There was no difference in the binding of Ang II to its putative receptors in all cell lines. Ang II increased intracellular inositol 1,4,5-triphosphate (IP3) in Neo3, but not in ATA5 and ATA21 cells. In contrast to MMCs and Neo3 cells, Ang II failed to stimulate proliferation in ATA5 and ATA21 clones as measured by [3H] thymidine incorporation and direct cell counts. However, ATA5 and ATA21 revealed a mitogenic response not different from MMCs after stimulation 2% or 10% of fetal calf serum. Treatment of ATA5 and ATA21 with 0.1 mM of the ATA-inhibitor amastatin or an ATA-inhibiting specific monoclonal antibody restored the proliferative effect of Ang II, suggesting that surface activity of ATA is involved in the attenuated mitogenesis in these cell. Our study demonstrates that it is feasible to overexpress Ang II-degrading enzymes in cultured mesangial cells and that this overexpression attenuated some effect of exogenous Ang II. These experiments are a first step toward the development of novel strategies to selectively antagonize locally generated Ang II in the kidney.
Wolf
G
G
Department of Medicine, University of Hamburg, Germany. Wolf@UKE.Uni-Hamburg.de
Assmann
K J
KJ
Stahl
R A
RA
D000626:Aminopeptidases / Q000502:physiology*; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D043384:Glutamyl Aminopeptidase; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis; D051379:Mice; D011945:Receptors, Angiotensin / Q000032:analysis
D011945:Receptors, Angiotensin; D000804:Angiotensin II; D015544:Inositol 1,4,5-Trisphosphate; D000626:Aminopeptidases; D043384:Glutamyl Aminopeptidase