title: Knockdown of natriuretic peptide receptor-A enhances receptor C expression and signalling in vascular smooth muscle cells.
abstract: OBJECTIVE
  Natriuretic peptide receptor-A (NPR-A) knockout mice exhibited an increased blood pressure that may also be attributed to the up-regulation of NPR-C and associated signalling; however, the interaction between the two receptors has not been investigated. In the present study, we investigated the effect of knockdown of NPR-A using NPR-A antisense (AS) on the expression of NPR-C and adenylyl cyclase (AC) signalling in A10 vascular smooth muscle cells (VSMC).
  
  
  RESULTS
  The receptor and G protein expression was determined by western blotting, and AC activity was determined by measuring [(32)P]cAMP formation from [α-(32)P]ATP. Treatment of A10 VSMC with NPR-A AS decreased NPR-A and enhanced NPR-C expression without altering the levels of angiotensin II AT1 and muscarinic M2 receptors. In addition, siRNA-NPR-A also resulted in the up-regulation of NPR-C. The re-expression of NPR-A in AS-treated cells reversed the enhanced expression of NPR-C to control levels. In addition, NPR-C-, AT1, and M2 receptor-mediated inhibition of AC and Giα protein expression was enhanced in AS-treated cells, whereas NPR-A-mediated cyclic GMP (cGMP) formation and Gsα-mediated stimulation of AC were significantly reduced. Pertussis toxin treatment attenuated the AS-induced enhanced inhibition of AC to control levels. Furthermore, the enhanced levels of NPR-C and Giα proteins were reversed to control levels by 8-bromo-cGMP (8Br-cGMP) and PD98059, an MEK inhibitor. In addition, 8Br-cGMP also attenuated AS-induced enhanced ERK1/2 phosphorylation to control levels.
  
  
  CONCLUSIONS
  These results demonstrate that knockdown of NPR-A up-regulates the expression of NPR-C, Giα proteins, and NPR-C-linked AC signalling and suggests a cross-talk between NPR-A and NPR-C.
authors: Department of Physiology, Faculty of Medicine,  University of Montreal, C.P. 6128, Succ. Centre-ville, Montreal, QC,  Canada H3C 3J7.
authors: Yuan
authors: Y
authors: Li
authors: Padma
authors: P
authors: Madiraju
authors: Madhu B
authors: MB
authors: Anand-Srivastava
mesh_terms: D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000502:physiology; D000818:Animals; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000032:analysis; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000502:physiology; D020935:MAP Kinase Signaling System; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D037342:Pertussis Toxin / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D020239:Receptor Cross-Talk; D044140:Receptor, Angiotensin, Type 1 / Q000032:analysis; D043585:Receptor, Muscarinic M2 / Q000032:analysis; D017461:Receptors, Atrial Natriuretic Factor / Q000032:analysis / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D034741:RNA, Small Interfering; D044140:Receptor, Angiotensin, Type 1; D043585:Receptor, Muscarinic M2; D037342:Pertussis Toxin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D000262:Adenylyl Cyclases; D017461:Receptors, Atrial Natriuretic Factor; C091715:atrial natriuretic factor receptor A; C073616:atrial natriuretic factor receptor C; D006152:Cyclic GMP