ClC-5, the electrogenic chloride/proton exchanger strongly expressed in renal proximal tubules, belongs to the endocytic macromolecular complex responsible for albumin and low-molecular-weight protein uptake. ClC-5 was found to be overexpressed in glomeruli of glomerulonephritis and in cultured human podocytes under albumin overload. The transcriptional regulation of human ClC-5 is not fully understood. Three functional promoters of various strengths and 11 different 5’ untranslated region (5’UTR) isoforms of CLCN5 messenger RNA (mRNA) were detected in the human kidney (variants 1–11). The aim of this study was to investigate the expression pattern of CLCN5 5’UTR variants and the CLCN5 common translated region in glomerulonephritis. The 5’UTR ends and the translated region of CLCN5 mRNA were analyzed using quantitative relative real-time PCR or quantitative comparative endpoint PCR with GAPDH as housekeeping gene in 8 normal kidneys and 12 renal biopsies from patients with glomerulonephritis. The expression profile for all variants in normal and glomerulonephritis biopsies was similar, and variant 3 and alternative variant 4 were the most abundantly expressed in both sets. In glomerulonephritis biopsies, isoforms under the control of a weak promoter (variants 4, 6 and 7) showed an increased expression leading to an increase in the CLCN5 translated region, underscoring their importance in kidney pathophysiology. Since weak promoters can be turned on by different stimuli, these data support the hypothesis that proteinuria could be one of the stimuli capable of starting a signaling pathway that induces an increase in CLCN5 transcription.
- gene expression
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MC and LG contributed equally.
Contributors FA and ET conceived the study. MC, LG and ET conducted the experiments. MC, LG and FA designed the experiments. LG, MC and DDP analyzed the data. GP provided assistance with the experimental methodology. MC, LG, FA and DDP wrote the manuscript. All authors approved the manuscript.
Funding This study was supported by the Rare Kidney Stone Consortium (5U54DK083908-04), which is part of the Rare Diseases Clinical Research Network (RDCRN), an initiative of the Office of Rare Diseases Research (ORDR). This consortium is funded through collaboration between the National Center for Advancing Translational Sciences (NCATS) and the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval All clinical investigations were conducted according to the principles expressed in the Declaration of Helsinki (latest revision 2013), and patients’ data were analyzed anonymously. All patients gave their informed, written consent. The study was approved by the ethics committee for experimental studies at Padua General Hospital, protocol number 0027778 (29/05/2012).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request. Clinical data and gene expression data will be available upon reasonable request by sending an email to firstname.lastname@example.org.
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