title: Cofilin interacts with ClC-5 and regulates albumin uptake in proximal tubule cell lines.
abstract: Receptor-mediated endocytosis is a constitutive high capacity pathway for the reabsorption of proteins from the glomerular filtrate by the renal proximal tubule. ClC-5 is a voltage-gated chloride channel found in the proximal tubule where it has been shown to be essential for protein uptake, based on evidence from patients with Dent's disease and studies in ClC-5 knockout mice. To further delineate the role of ClC-5 in albumin uptake, we performed a yeast two-hybrid screen with the C-terminal tail of ClC-5 to identify any interactions of the channel with proteins involved in endocytosis. We found that the C-terminal tail of ClC-5 bound the actin depolymerizing protein, cofilin, a result that was confirmed by GST-fusion pulldown assays. In cultured proximal tubule cells, cofilin was distributed in nuclear, cytoplasmic, and microsomal fractions and co-localized with ClC-5. Phosphorylation of cofilin by overexpressing LIM kinase 1 resulted in a stabilization of the actin cytoskeleton. Phosphorylation of cofilin in two proximal tubule cell models (porcine renal proximal tubule and opossum kidney) was also accompanied by a pronounced inhibition of albumin uptake. This study identifies a novel interaction between the C-terminal tail of ClC-5 and cofilin, an actin-associated protein that is crucial in the regulation of albumin uptake by the proximal tubule.
authors.affiliation: Department of Physiology, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA
authors.forename: Deanne H
authors.initials: DH
authors.lastname: Hryciw
authors.forename: Yinghong
authors.initials: Y
authors.lastname: Wang
authors.forename: Olivier
authors.initials: O
authors.lastname: Devuyst
authors.forename: Carol A
authors.initials: CA
authors.lastname: Pollock
authors.forename: Philip
authors.initials: P
authors.lastname: Poronnik
authors.forename: William B
authors.initials: WB
authors.lastname: Guggino
mesh_terms: D051339:Actin Depolymerizing Factors; D000199:Actins / Q000378:metabolism; D000418:Albumins / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D001693:Biological Transport, Active; D002460:Cell Line; D018118:Chloride Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D018374:LLC-PK1 Cells; D054461:Lim Kinases; D051379:Mice; D008840:Microfilament Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009893:Opossums; D010766:Phosphorylation; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013552:Swine; D020798:Two-Hybrid System Techniques
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D000418:Albumins; C097503:CLC-5 chloride channel; D018118:Chloride Channels; D004268:DNA-Binding Proteins; D008840:Microfilament Proteins; D011993:Recombinant Fusion Proteins; D011494:Protein Kinases; C515892:LIMK1 protein, human; D054461:Lim Kinases; C515893:Limk1 protein, mouse; D017346:Protein Serine-Threonine Kinases