title: Hypertonicity increases CLC-5 expression in mouse medullary thick ascending limb cells.
abstract: Genetic studies indicated that mutations of the chloride channel CLC-5 in the kidney are responsible for a group of clinical disorders, collectively called Dent's disease. In the kidney, CLC-5 was found to be expressed in the proximal tubule, medullary thick ascending limb (mTAL) of loop of Henle, and intercalated cells of the collecting tubule. In proximal tubular cells, CLC-5 was found to play an important role in receptor-mediated endocytosis. However, the functional roles of CLC-5 in mTAL and collecting tubules remain unclear. Because mTAL is normally exposed to a hypertonic environment, we aimed to examine the effect of hypertonicity on CLC-5 expression in this nephron segment. Our studies revealed that exposure to hypertonicity (up to 550 mosM) increased CLC-5 mRNA and protein levels in a murine mTAL cell line (MTAL) but not in an opossum kidney (OK) proximal tubular cell line. A similar effect was also found in mouse kidneys, where CLC-5 expression was enhanced in renal medulla, but not cortex, after 48 h of water deprivation. We also tested the effect of hypertonicity on endocytotic activity and found that exposure to hypertonicity caused a significant decrease in cellular uptake of FITC-labeled albumin in OK but not in MTAL cells. Our results suggest that CLC-5 expression is upregulated by hypertonicity in mTAL cells but not in proximal tubular cells. We speculate that the increased CLC-5 levels in mTAL may serve to maintain the endocytotic activity in a hypertonic environment.
authors.affiliation: Renal Division, Department of Medicine, Olive View-UCLA Medical Center, Sylmar, CA 91342, USA. pctp@ucla.edu
authors.forename: Phuong-Chi
authors.initials: PC
authors.lastname: Pham
authors.forename: Olivier
authors.initials: O
authors.lastname: Devuyst
authors.forename: Phuong-Thu
authors.initials: PT
authors.lastname: Pham
authors.forename: Naoko
authors.initials: N
authors.lastname: Matsumoto
authors.forename: Remi N G
authors.initials: RN
authors.lastname: Shih
authors.forename: Oak D
authors.initials: OD
authors.lastname: Jo
authors.forename: Norimoto
authors.initials: N
authors.lastname: Yanagawa
authors.forename: Adam M
authors.initials: AM
authors.lastname: Sun
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D018118:Chloride Channels / Q000235:genetics* / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology; D015870:Gene Expression; D006982:Hypertonic Solutions / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000166:cytology; D008138:Loop of Henle / Q000166:cytology / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009893:Opossums; D012333:RNA, Messenger / Q000378:metabolism; D014868:Water Deprivation / Q000502:physiology*
chemical_list: C097503:CLC-5 chloride channel; D018118:Chloride Channels; D006982:Hypertonic Solutions; D012333:RNA, Messenger