Renal proximal tubule Na,K-ATPase is controlled by CREB-regulated transcriptional coactivators as well as salt-inducible kinase 1

Abstract

Sodium reabsorption by the kidney is regulated by locally produced natriuretic and anti-natriuretic factors, including dopamine and norepinephrine, respectively. Previous studies indicated that signaling events initiated by these natriuretic and anti-natriuretic factors achieve their effects by altering the phosphorylation of Na,K-ATPase in the renal proximal tubule, and that Protein Kinase A (PKA) and Calcium mediated signaling pathways are involved. The same signaling pathways also control the transcription of the Na,K-ATPase β subunit gene atp1b1 in renal proximal tubule cells. In this report, evidence is presented that 1) both the recently discovered cAMP-Regulated Transcriptional Coactivators (CRTCs), and Salt Inducible Kinase 1 (SIK1) contribute to the transcriptional regulation of atp1b1 in renal proximal tubule (RPT) cells, and 2) that renal effectors including norepinephrine, dopamine, prostaglandins and sodium play a role. Exogenously expressed CRTCs stimulate atp1b1 transcription. Evidence for a role of endogenous CRTCs includes the loss of transcriptional regulation of atp1b1 by a dominant negative CRTC, as well as by a CREB mutant, with an altered CRTC binding site. In a number of experimental systems, SIK phosphorylates CRTCs, which are then sequestered in the cytoplasm, preventing their nuclear effects. Consistent with such a role of SIK in primary RPT cells, atp1b1 transcription increased in the presence of a dominant negative SIK1, and in addition, regulation by dopamine, norepinephrine and monensin was disrupted by a dominant negative SIK1. These latter observations can be explained, if SIK1 is phosphorylated and inactivated in the presence of these renal effectors. Our results support the hypothesis that Na,K-ATPase in the renal proximal tubule is regulated at the transcriptional level via SIK1 and CRTCs by renal effectors, in addition to the previously reported control of the phosphorylation of Na,K-ATPase.

Data on Na,K-ATPase in primary cultures of renal proximal tubule cells treated with catecholamines

“…Following a chronic incubation with guanabenz, an α adrenergic agonist, an increase in Na,K-ATPase α and β subunit mRNAs was observed. This data supports the research article entitled, “Renal proximal tubule Na, K-ATPase is controlled by CREB regulated transcriptional coactivators as well as salt inducible kinase 1” (Taub et al 2015) [1] .…”

“…Primary cultures of rabbit kidney proximal tubule cells, were prepared as described previously [1 , 2] . Rabbits employed to obtain the primary cultures were used by procedures approved by the University at Buffalo Institutional Animal Care and Use Committee.…”

Gene Level Regulation of Na,K-ATPase in the Renal Proximal Tubule Is Controlled by Two Independent but Interacting Regulatory Mechanisms Involving Salt Inducible Kinase 1 and CREB-Regulated Transcriptional Coactivators

“…Consistent with the involvement of CRTCs, CRTC expression vectors (encoding for either CRTC1, CRTC2, or CRTC3) stimulated transcription in transient transfection studies with pHβ1-1141 Luc (a human Na,K-ATPase β1 promoter/luciferase construct) [ 6 , 38 ]. Initially, it was unclear which of these CRTCs was responsible for stimulating atp1b1 transcription, because Western analyses indicated that all three CRTCs are expressed in MDCK cells, as well as in primary cultures of rabbit RPT cells.…”

“…Initial studies concerning ouabain and signaling were conducted with cardiomyocytes. This report is concerned with Na,K-ATPase signaling by the CRTC/SIK1 pathway in the kidney, specifically the RPT [ 6 ].…”

Analysing the Expression of Eight Clock Genes in Five Tissues From Fasting and Fed Sows

“…In addition, this transcription factor regulates cell proliferation and differentiation ( Shen et al, 1997 ), adipogenesis ( Ozaki et al, 2012 ), cytokine production by T cells ( Lin et al, 2014 ), apoptosis ( Qian et al, 2012 ) and cellular senescence ( Qian et al, 2008 ). Similarly, the SIK1 gene performs a broad variety of functions related with inflammation ( Lombardi et al, 2016 ), steroidogenesis ( Hu et al, 2015 ), renal function ( Taub et al, 2015 ), vascular remodelling ( Bertorello et al, 2015 ) and glucose metabolism ( Patel et al, 2014 ), to mention a few, so its biological role goes far beyond the modulation of circadian rhythms and this is reflected in its variable pattern of expression across porcine tissues.…”