The natriuretic effect of uroguanylin (UGN) involves reduction of proximal tubule (PT) sodium reabsorption. However, the target sodium transporters as well as the molecular mechanisms involved in these processes remain poorly understood.
To address the effects on UGN on PT (Na(+)+K(+))ATPase and the signal transduction pathways involved in this effect, we used LLC-PK1 cells. The effects of UGN were determined through ouabain-sensitive ATP hydrolysis and immunoblotting assays during different experimental conditions.
We observed that UGN triggers cGMP/PKG and cAMP/PKA pathways in a sequential way. The activation of PKA leads to the inhibition of mTORC2 activity, PKB phosphorylation at S473, PKB activity and, consequently, a decrease in the mTORC1/S6K pathway. The final effects are decreased expression of the α1 subunit of (Na(+)+K(+))ATPase and inhibition of enzyme activity.
These results suggest that the molecular mechanism of action of UGN on sodium reabsorption in PT cells is more complex than previously thought. We propose that PKG-dependent activation of PKA leads to the inhibition of mTORC2/PKB/mTORC1/S6K pathway, an important signaling pathway involved in the mantainence of the PT sodium pump expression and activity.
The current results expand our understanding of the signal transduction pathways involved in the overall effect of UGN on renal sodium excretion.
Biochimica et biophysica acta. 2016 Apr 18 [Epub ahead of print]
Francisco J Arnaud-Batista, Diogo B Peruchetti, Thiago P Abreu, Nilberto R F do Nascimento, Gerhard Malnic, Manasses C Fonteles, Celso Caruso-Neves
Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Avenida Carlos Chagas Filho, 373, Cidade Universitária, Rio de Janeiro, Rio de Janeiro 21941-902, Brazil; Instituto Superior de Ciências Biomédicas, Universidade Estadual do Ceará, Avenida Dr. Silas Munguba, 1700, Campus do Itaperi, Fortaleza, Ceará 60714-903, Brazil., Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Avenida Carlos Chagas Filho, 373, Cidade Universitária, Rio de Janeiro, Rio de Janeiro 21941-902, Brazil., Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Avenida Carlos Chagas Filho, 373, Cidade Universitária, Rio de Janeiro, Rio de Janeiro 21941-902, Brazil., Instituto Superior de Ciências Biomédicas, Universidade Estadual do Ceará, Avenida Dr. Silas Munguba, 1700, Campus do Itaperi, Fortaleza, Ceará 60714-903, Brazil., Instituto de Ciências Biomédicas, Universidade de São Paulo, Avenida Prof. Lineu Prestes, 1524, Cidade Universitária "Armando Salles Oliveira", São Paulo, São Paulo 05508-900, Brazil., Instituto Superior de Ciências Biomédicas, Universidade Estadual do Ceará, Avenida Dr. Silas Munguba, 1700, Campus do Itaperi, Fortaleza, Ceará 60714-903, Brazil., Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Avenida Carlos Chagas Filho, 373, Cidade Universitária, Rio de Janeiro, Rio de Janeiro 21941-902, Brazil; Instituto Nacional de Ciência e Tecnologia em Biologia e Bioimagem, Avenida Carlos Chagas Filho, 373, Cidade Universitária, Rio de Janeiro, Rio de Janeiro 21941-902, Brazil. Electronic address: .