C-Peptide Increases Na,K-ATPase Expression via PKC- and MAP Kinase-Dependent Activation of Transcription Factor ZEB in Human Renal Tubular CellsReportar como inadecuado




C-Peptide Increases Na,K-ATPase Expression via PKC- and MAP Kinase-Dependent Activation of Transcription Factor ZEB in Human Renal Tubular Cells - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Background

Replacement of proinsulin C-peptide in type 1 diabetes ameliorates nerve and kidney dysfunction, conditions which are associated with a decrease in Na,K-ATPase activity. We determined the molecular mechanism by which long term exposure to C-peptide stimulates Na,K-ATPase expression and activity in primary human renal tubular cells HRTC in control and hyperglycemic conditions.

Methodology-Principal Findings

HRTC were cultured from the outer cortex obtained from patients undergoing elective nephrectomy. Ouabain-sensitive rubidium 86Rb+ uptake and Na,K-ATPase activity were determined. Abundance of Na,K-ATPase was determined by Western blotting in intact cells or isolated basolateral membranes BLM. DNA binding activity was determined by electrical mobility shift assay EMSA. Culturing of HRTCs for 5 days with 1 nM, but not 10 nM of human C-peptide leads to increase in Na,K-ATPase α1-subunit protein expression, accompanied with increase in 86Rb+ uptake, both in normal- and hyperglycemic conditions. Na,K-ATPase α1-subunit expression and Na,K-ATPase activity were reduced in BLM isolated from cells cultured in presence of high glucose. Exposure to1 nM, but not 10 nM of C-peptide increased PKCε phosphorylation as well as phosphorylation and abundance of nuclear ERK1-2 regardless of glucose concentration. Exposure to 1 nM of C-peptide increased DNA binding activity of transcription factor ZEB AREB6, concomitant with Na,K-ATPase α1-subunit mRNA expression. Effects of 1 nM C-peptide on Na,K-ATPase α1-subunit expression and-or ZEB DNA binding activity in HRTC were abolished by incubation with PKC or MEK1-2 inhibitors and ZEB siRNA silencing.

Conclusions-Significance

Despite activation of ERK1-2 and PKC by hyperglycemia, a distinct pool of PKCs and ERK1-2 is involved in regulation of Na,K-ATPase expression and activity by C-peptide. Most likely C-peptide stimulates sodium pump expression via activation of ZEB, a transcription factor that has not been previously implicated in C-peptide-mediated signaling. Importantly, only physiological concentrations of C-peptide elicit this effect.



Autor: Dana Galuska, Sergej Pirkmajer, Romain Barrès, Karin Ekberg, John Wahren, Alexander V. Chibalin

Fuente: http://plos.srce.hr/



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