Angiotensin II-induced activation of c-Ret signaling is critical in ureteric bud branching morphogenesis.
The renin-angiotensin system (RAS) plays a critical role in ureteric bud (UB) and kidney morphogenesis. Mutations in the genes encoding components of the RAS cause a spectrum of congenital abnormalities of the kidney and urinary tract (CAKUT). However, the mechanisms by which aberrations in the RAS result in CAKUT are poorly understood. Given that c-Ret receptor tyrosine kinase (RTK) is a major inducer of UB branching, the present study tested the hypothesis that angiotensin (Ang) II-induced activation of c-Ret plays a critical role in UB branching morphogenesis. E12.5 mice metanephroi were grown for 24h in the presence or absence of Ang II, Ang II AT(1) receptor (AT(1)R) antagonist candesartan, phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 or ERK1/2 inhibitor PD98059. Ang II increased the number of UB tips (61+/-2.4 vs. 45+/-4.3, p<0.05) compared with control. Quantitative RT-PCR analysis demonstrated that Ang II increased c-Ret mRNA levels in the kidney (1.35+/-0.05 vs. 1.0+/-0, p<0.01) and in the UB cells (1.28+/-0.04 vs. 1.0+/-0, p<0.01) compared to control. This was accompanied by increased Tyr(1062)Ret phosphorylation by Ang II (5.5+/-0.9 vs. 1.8+/-0.4 relative units, p<0.05). In addition, treatment of UB cells with Ang II (10(-5)M) increased phosphorylation of Akt compared to control (213+/-16 vs. 100+/-20%, p<0.05). In contrast, treatment of metanephroi or UB cells with candesartan decreased c-Ret mRNA levels (0.72+/-0.06 vs. 1.0+/-0, p<0.01; 0.68+/-0.07 vs. 1.0+/-0, p<0.05, respectively) compared with control. Ang II-induced UB branching was abrogated by LY294002 (24+/-2.6 vs. 37+/-3.0, p<0.05) or PD98059 (33+/-2.0 vs. 48+/-2.2, p<0.01). These data demonstrate that Ang II-induced UB branching depends on activation of Akt and ERK1/2. We conclude that cross-talk between the RAS and c-Ret signaling plays an important role in the development of the renal collecting system.
Song
Renfang
R
Department of Pediatrics, Hypertension and Renal Center of Excellence, Tulane University Health Sciences Center, New Orleans, LA 70112, USA.
Spera
Melissa
M
Garrett
Colleen
C
Yosypiv
Ihor V
IV
D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D002867:Chromones / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors; D005419:Flavonoids / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D009924:Organ Culture Techniques / Q000379:methods; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051096:Proto-Oncogene Proteins c-ret / Q000378:metabolism*; D012084:Renin-Angiotensin System; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014513:Ureter / Q000196:embryology* / Q000502:physiology; D018631:ras Proteins / Q000378:metabolism
D002867:Chromones; D005419:Flavonoids; D009025:Morpholines; D000804:Angiotensin II; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019869:Phosphatidylinositol 3-Kinases; D051096:Proto-Oncogene Proteins c-ret; D048049:Extracellular Signal-Regulated MAP Kinases; D018631:ras Proteins; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one