Deficiency of polycystic kidney disease-1 gene (PKD1) expression increases A3 adenosine receptors in human renal cells: Implications for cAMP-dependent signalling and proliferation of PKD1-mutated cystic cells

Abstract

Cyst growth and expansion in autosomal dominant polycystic kidney disease (ADPKD) has been attributed to numerous factors, including ATP, cAMP and adenosine signalling. Although the role of ATP and cAMP has been widely investigated in PKD1-deficient cells, no information is currently available on adenosine-mediated signalling. Here we investigate for the first time the impact of abnormalities of polycystin-1 (PC1) on the expression and functional activity of adenosine receptors, members of the G-protein-coupled receptor superfamily. Pharmacological, molecular and biochemical findings show that a siRNA-dependent PC1-depletion in HEK293 cells and a PKD1-nonsense mutation in cyst-derived cell lines result in increased expression of the A(3) adenosine receptor via an NFkB-dependent mechanism. Interestingly, A(3) adenosine receptor levels result higher in ADPKD than in normal renal tissues. Furthermore, the stimulation of this receptor subtype with the selective agonist Cl-IB-MECA causes a reduction in both cytosolic cAMP and cell proliferation in both PC1-deficient HEK293 cells and cystic cells. This reduction is associated with increased expression of p21(waf) and reduced activation not only of ERK1/2, but also of S6 kinase, the main target of mTOR signalling. In the light of these findings, the ability of Cl-IB-MECA to reduce disease progression in ADPKD should be further investigated. Moreover, our results suggest that NFkB, which is markedly activated in PC1-deficient and cystic cells, plays an important role in modulating A(3)AR expression in cystic cells.

Purinergic signalling in the kidney in health and disease

“…It has been proposed that ATP is released from monocilia to act as an autocrine regulator via P2 receptors [138]. Deficiency of PKD-1 gene expression increases A 3 receptors in human renal cells [2]. The potential for cyst formation has been examined for two MDCK cell subclones, C7 cells that resemble principal cells and C11 cells that resemble α-intercalated cells [36].…”

The Dark Side of Extracellular ATP in Kidney Diseases

“…54 As far as the involvement of the adenosine receptor in polycystic kidney disease, PKD1-mutated cystic cells express increased levels of adenosine A 3A receptors. 55 Thus, cyst growth and expansion in polycystic kidney disease may be worsened by eATP and adenosine-mediated signaling, but it remains unclear whether this may lead to a clinically relevant therapeutic strategy.…”

Multidrug Therapy for Polycystic Kidney Disease: A Review and Perspective

“…Furthermore, cAMP levels may be also reduced by the stimulation of adenosine type 3 receptors (A3AR) which inhibits adenylyl cyclase and are overexpressed in ADPKD cystic cells and tissues [30]. The specific A3AR agonist Cl-IB-MECA is able to reduce cell proliferation by reduction of cAMP levels and ERK activity in ADPKD cystic cells [30].…”

“…The specific A3AR agonist Cl-IB-MECA is able to reduce cell proliferation by reduction of cAMP levels and ERK activity in ADPKD cystic cells [30]. Future studies on ADPKD animal models are necessary to establish if Cl-IB-MECA is effective also in vivo.…”