title: SOCS-3 is downregulated in progressive CKD patients and regulates proliferation in human renal proximal tubule cells in a STAT1/3 independent manner.
abstract: Proliferation and the sequence of epithelial to mesenchymal transition (EMT) and mesenchymal to epithelial transition (MET), called epithelial-mesenchymal-epithelial (EME) cycling are pivotal mechanisms of kidney repair and fibrosis. Furthermore, data suggest that dedifferentiation (EMT) is a prerequisite for proliferation of tubule cells. These processes have been shown to be regulated by STAT1/3 signaling. Suppressor of cytokine signaling-3 (SOCS-3) is a negative regulator of STAT1/3 signaling. Using a transcriptomics data set of patients with proteinuric kidney diseases we found that low levels of SOCS-3 RNA were associated with high-serum creatinine values in the long-term follow-up, which suggested a role of SOCS-3, regulated signaling in progression of chronic kidney disease. This result was validated in an independent cohort of patients with proteinuric nephropathies on protein level. In addition ∼60% of STAT target genes were differentially expressed in relation to stable kidney disease patients. Using two renal cellular models and SOCS-3 knockdown by short interfering RNA we investigated SOCS-3 effects on oncostatin M-induced STAT activation, differentiation and proliferation. SOCS-3 knockdown resulted in enhanced pSTAT1/3 phosphorylation and epithelial differentiation. The latter effect was only slightly enhanced by OSM treatment. Cellular proliferation was inhibited after SOCS-3 knockdown. This effect could not be further stimulated by OSM. Effects of SOCS-3 knockdown were not enhanced by downregulation of STAT1/3, suggesting a STAT independent effect on cell cycle regulators. Indeed, knockdown and overexpression of SOCS-3 were associated with decrease and increase of cyclin D1, -E and proliferation, respectively. In summary, SOCS-3 inhibits phosphorylation of pSTAT1/3 in renal tubule cells. Additionally, we show for the first time that-in vivo-loss of SOCS-3 is associated with unfavorable prognosis. In vitro, downregulation of SOCS-3 inhibits dedifferentiation (EMT) and cellular proliferation in kidney proximal tubule cells.
authors.affiliation: Department of Internal Medicine IV, Nephrology and Hypertension, Medical University Innsbruck, Innsbruck, Austria. Hannes.Neuwirt@i-med.ac.at
authors.forename: Hannes
authors.initials: H
authors.lastname: Neuwirt
authors.forename: Iris E
authors.initials: IE
authors.lastname: Eder
authors.forename: Martin
authors.initials: M
authors.lastname: Puhr
authors.forename: Michael
authors.initials: M
authors.lastname: Rudnicki
mesh_terms: D000328:Adult; D000818:Animals; D048708:Cell Growth Processes / Q000502:physiology; D002460:Cell Line; D019938:Cyclin D1 / Q000378:metabolism; D019927:Cyclin E / Q000378:metabolism; D015536:Down-Regulation; D005260:Female; D055785:Gene Knockdown Techniques; D006801:Humans; D007150:Immunohistochemistry; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D051436:Renal Insufficiency, Chronic / Q000378:metabolism* / Q000473:pathology; D015203:Reproducibility of Results; D050794:STAT1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D018709:Statistics, Nonparametric; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism*; D013552:Swine; D046888:Tissue Array Analysis
chemical_list: D019927:Cyclin E; C106644:SOCS3 protein, human; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D019938:Cyclin D1