title: Angiotensin II signaling and HB-EGF shedding via metalloproteinase in glomerular mesangial cells.
abstract: BACKGROUND
  Angiotensin II (Ang II) has been implicated in the development of glomerulosclerosis by stimulating fibronectin (FN) synthesis. The processing and release of heparin binding-endothelin growth factor (HB-EGF) are activated by protein kinase C (PKC) and Ca2+ signaling. We studied the roles of HB-EGF and endothelial growth factor (EGF) receptor (EGFR) in Ang II-induced FN expression using mesangial cells.
  
  
  METHODS
  Mesangial cells were prepared from mouse kidneys by the explant method and cells were used at passages 4 and 5.
  
  
  RESULTS
  Ang II stimulated FN mRNA levels dose-dependently with a maximal increase (3.4-fold) after 12 hours of incubation. This action was completely inhibited by PKC inhibitors and slightly blocked by Ca2+ chelating agents. FN mRNA accumulation by Ang II was abolished by tyrosine kinase inhibitors, a specific inhibitor for EGFR (AG1478) and extracellular signal-regulated kinase (ERK) inactivation. Addition of neutralizing anti-HB-EGF antibody, as well as pretreatment with heparin or the metalloproteinase inhibitor batimastat abolished induction of FN expression by Ang II. In mesangial cells stably transfected with a chimeric construct containing HB-EGF and alkaline phosphatase (ALP) genes, ALP activity in incubation medium was rapidly increased by Ang II (1.7-fold at 0.5 min) and reached a 4.1-fold increase at two minutes. Ang II phosphorylated EGFR (maximal at 2 min) and ERK (maximal at 8 min) in a PKC- and metalloproteinase-dependent manner. Ang II stimulated the expression and release of transforming growth factor-beta (TGF-beta) via EGFR-mediated signaling, and the released TGF-beta also contributed to Ang II-mediated FN expression via EGFR transactivation.
  
  
  CONCLUSIONS
  Ang II-mediated FN expression was regulated by autocrine effects of HB-EGF and TGF-beta, suggesting a novel paradigm for cross-talk between Ang II and growth factor receptor signaling pathways.
authors.affiliation: Department of Medicine II, Kansai Medical University, Osaka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Uchiyama-Tanaka
authors.forename: H
authors.initials: H
authors.lastname: Matsubara
authors.forename: Y
authors.initials: Y
authors.lastname: Nozawa
authors.forename: S
authors.initials: S
authors.lastname: Murasawa
authors.forename: Y
authors.initials: Y
authors.lastname: Mori
authors.forename: A
authors.initials: A
authors.lastname: Kosaki
authors.forename: K
authors.initials: K
authors.lastname: Maruyama
authors.forename: H
authors.initials: H
authors.lastname: Masaki
authors.forename: Y
authors.initials: Y
authors.lastname: Shibasaki
authors.forename: S
authors.initials: S
authors.lastname: Fujiyama
authors.forename: A
authors.initials: A
authors.lastname: Nose
authors.forename: O
authors.initials: O
authors.lastname: Iba
authors.forename: T
authors.initials: T
authors.lastname: Hasagawa
authors.forename: E
authors.initials: E
authors.lastname: Tateishi
authors.forename: S
authors.initials: S
authors.lastname: Higashiyama
authors.forename: T
authors.initials: T
authors.lastname: Iwasaka
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D002478:Cells, Cultured; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000502:physiology; D005353:Fibronectins / Q000235:genetics; D005920:Glomerular Mesangium / Q000166:cytology / Q000378:metabolism*; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D008666:Metalloendopeptidases / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism / Q000502:physiology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D044140:Receptor, Angiotensin, Type 1; D011945:Receptors, Angiotensin / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000235:genetics; D015854:Up-Regulation
chemical_list: D005353:Fibronectins; C587884:Hbegf protein, mouse; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D011945:Receptors, Angiotensin; D016212:Transforming Growth Factor beta; D000804:Angiotensin II; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D008666:Metalloendopeptidases; D013755:Tetradecanoylphorbol Acetate