title: Inducible Expression of Claudin-1 in Glomerular Podocytes Generates Aberrant Tight Junctions and Proteinuria through Slit Diaphragm Destabilization.
abstract: The tight junction (TJ) has a key role in regulating paracellular permeability to water and solutes in the kidney. However, the functional role of the TJ in the glomerular podocyte is unclear. In diabetic nephropathy, the gene expression of claudins, in particular claudin-1, is markedly upregulated in the podocyte, accompanied by a tighter filtration slit and the appearance of TJ-like structures between the foot processes. However, there is no definitive evidence to show slit diaphragm (SD) to TJ transition in vivo Here, we report the generation of a claudin-1 transgenic mouse model with doxycycline-inducible transgene expression specifically in the glomerular podocyte. We found that induction of claudin-1 gene expression in mature podocytes caused profound proteinuria, and with deep-etching freeze-fracture electron microscopy, we resolved the ultrastructural change in the claudin-1-induced SD-TJ transition. Notably, immunolabeling of kidney proteins revealed that claudin-1 induction destabilized the SD protein complex in podocytes, with significantly reduced expression and altered localization of nephrin and podocin proteins. Mechanistically, claudin-1 interacted with both nephrin and podocin through cis- and trans-associations in cultured cells. Furthermore, the rat puromycin aminonucleoside nephrosis model, previously suspected of undergoing SD-TJ transition, exhibited upregulated expression levels of claudin-1 mRNA and protein in podocytes. Together, our data attest to the novel concept that claudins and the TJ have essential roles in podocyte pathophysiology and that claudin interactions with SD components may facilitate SD-TJ transition that appears to be common to many nephrotic conditions.
authors.affiliation: Department of Internal Medicine, Renal Division, ygong@dom.wustl.edu jhou@wustl.edu.|Department of Cell Biology, Center for Investigation of Membrane Excitability Diseases, and.
authors.forename: Yongfeng
authors.initials: Y
authors.lastname: Gong
authors.affiliation: Department of Internal Medicine, Renal Division.|Department of Cell Biology, Center for Investigation of Membrane Excitability Diseases, and.
authors.forename: Abby
authors.initials: A
authors.lastname: Sunq
authors.affiliation: Department of Cell Biology, Washington University Medical School, St. Louis, Missouri.
authors.forename: Robyn A
authors.initials: RA
authors.lastname: Roth
authors.affiliation: Department of Internal Medicine, Renal Division, ygong@dom.wustl.edu jhou@wustl.edu.|Department of Cell Biology, Center for Investigation of Membrane Excitability Diseases, and.
authors.forename: Jianghui
authors.initials: J
authors.lastname: Hou
mesh_terms: D000818:Animals; D062445:Claudin-1 / Q000096:biosynthesis*; D007678:Kidney Glomerulus / Q000166:cytology; D008297:Male; D050199:Podocytes / Q000378:metabolism* / Q000648:ultrastructure*; D011507:Proteinuria / Q000209:etiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019108:Tight Junctions / Q000473:pathology*
chemical_list: D062445:Claudin-1
keywords: claudin; podocyte; protein interaction; proteinuria; slit diaphragm; tight junction