Transactivation of the epidermal growth factor receptor by angiotensin II in glomerular podocytes

Nephron Exp Nephrol. 2006;103(3):e109-18. doi: 10.1159/000092196. Epub 2006 Mar 22.

Abstract

Background/aims: Activation of angiotensin II (ANG2) receptors stimulates extracellular signal-regulated kinases (ERKs) that, in some cell systems, are mediated by transactivating the epidermal growth factor (EGF) receptor (EGFR) through mechanisms involving matrix metalloprotease (MMP)-stimulated processing of heparin-binding EGF (HB-EGF) from its precursor.

Methods: The signaling pathways linked to ANG2-dependent ERK activation were determined in an immortalized mouse podocyte cell line by monitoring ANG2-stimulated phosphorylation of ERK1/2.

Results: ANG2 induced transient ERK phosphorylation that was maximal at 5 min and then rapidly dissipated. ANG2-dependent ERK activation was inhibited by: (1) the type-1 ANG2-selective antagonist losartan; (2) the type-2 ANG2-selective antagonist PD123319; (3) an inhibitor of MMP2/9; (4) the EGFR kinase inhibitor AG1478, and (5) the HB-EGF antagonists CRM197 and heparin. ANG2-dependent ERK activation was mediated by both protein kinase C (PKC)- and calcium-dependent mechanisms and was associated with tyrosine phosphorylation of EGFR. To determine if ANG2-dependent HB-EGF release could act in a paracrine fashion on adjacent cells, HEK293 cells were stably transfected with green fluorescent protein-tagged ERK2 (GFP-ERK2). In stably transfected HEK293 cells, EGF stimulated phosphorylation of endogenous ERK1/2 as well as GFP-ERK2. In contrast, ANG2 had no effect on ERK phosphorylation in stably transfected HEK293 cells. When podocytes were co-cultured with stably transfected HEK293 cells, however, treatment with ANG2 rapidly stimulated GFP-ERK2 phosphorylation. Both the MMP2/9 inhibitor and AG1478 attenuated ANG2-dependent phosphorylation of GFP-ERK2 in the co-culture system.

Conclusions: These data indicate that ERK activation is induced by ANG2 in podocytes by mechanisms involving ANG2-dependent release of HB-EGF which, in turn, may act in an autocrine and paracrine fashion to stimulate ERK activity.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Angiotensin II / pharmacology*
  • Angiotensin II Type 1 Receptor Blockers / pharmacology
  • Angiotensin II Type 2 Receptor Blockers
  • Animals
  • Cell Line
  • Coculture Techniques
  • Enzyme Activation / drug effects
  • Enzyme Activation / physiology
  • Epidermal Growth Factor / metabolism
  • Epidermal Growth Factor / pharmacology
  • ErbB Receptors / genetics*
  • Green Fluorescent Proteins / genetics
  • Heparin-binding EGF-like Growth Factor
  • Humans
  • Imidazoles / pharmacology
  • Intercellular Signaling Peptides and Proteins
  • Kidney Glomerulus / cytology
  • Kidney Glomerulus / metabolism*
  • Losartan / pharmacology
  • Metalloproteases / antagonists & inhibitors
  • Mice
  • Mitogen-Activated Protein Kinase 1 / genetics
  • Mitogen-Activated Protein Kinases / metabolism
  • Phosphorylation / drug effects
  • Podocytes / drug effects*
  • Podocytes / metabolism*
  • Protease Inhibitors / pharmacology
  • Pyridines / pharmacology
  • Recombinant Fusion Proteins / metabolism
  • Time Factors
  • Transcriptional Activation*

Substances

  • Angiotensin II Type 1 Receptor Blockers
  • Angiotensin II Type 2 Receptor Blockers
  • HBEGF protein, human
  • Hbegf protein, mouse
  • Heparin-binding EGF-like Growth Factor
  • Imidazoles
  • Intercellular Signaling Peptides and Proteins
  • Protease Inhibitors
  • Pyridines
  • Recombinant Fusion Proteins
  • Angiotensin II
  • PD 123319
  • Green Fluorescent Proteins
  • Epidermal Growth Factor
  • ErbB Receptors
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinases
  • Metalloproteases
  • Losartan