title: Mature N-linked glycans facilitate UT-A1 urea transporter lipid raft compartmentalization.
abstract: The UT-A1 urea transporter is a glycoprotein with two different glycosylated forms of 97 and 117 kDa. In this study, we found the 117-kDa UT-A1 preferentially resides in lipid rafts, suggesting that the glycosylation status may interfere with UT-A1 lipid raft trafficking. This was confirmed by a site-directed mutagenesis study in MDCK cells. The nonglycosylated UT-A1 showed reduced localization in lipid rafts. By using sugar-specific binding lectins, we further found that the UT-A1 in nonlipid rafts contained a high amount of mannose, as detected by concanavalin A, while the UT-A1 in lipid rafts was the mature N-acetylglucosamine-containing form, as detected by wheat germ agglutinin. In the inner medulla (IM) of diabetic rats, the more abundant 117-kDa UT-A1 in lipid rafts was the mature glycosylation form, with high amounts of N-acetylglucosamine and sialic acid. In contrast, in the IM of normal rats, the predominant 97-kDa UT-A1 was the form enriched in mannose. Functionally, inhibition of glycosylation by tunicamycin or elimination of the glycosylation sites by mutation significantly reduced UT-A1 activity in oocytes. Taken together, our study reveals a new role of N-linked glycosylation in regulating UT-A1 activity by promoting UT-A1 trafficking into membrane lipid raft subdomains.
authors.affiliation: Renal Division, Department of Medicine, Emory University, Atlanta, GA 30322, USA. gchen3@emory.edu
authors.forename: Guangping
authors.initials: G
authors.lastname: Chen
authors.forename: Ashley G
authors.initials: AG
authors.lastname: Howe
authors.forename: Gang
authors.initials: G
authors.lastname: Xu
authors.forename: Otto
authors.initials: O
authors.lastname: Fröhlich
authors.forename: Janet D
authors.initials: JD
authors.lastname: Klein
authors.forename: Jeff M
authors.initials: JM
authors.lastname: Sands
mesh_terms: D000818:Animals; D002451:Cell Compartmentation; D002460:Cell Line; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism; D004285:Dogs; D005260:Female; D006031:Glycosylation; D066298:In Vitro Techniques; D007685:Kidney Tubules, Collecting / Q000378:metabolism; D008297:Male; D021962:Membrane Microdomains / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012794:Sialic Acids / Q000737:chemistry; D014981:Xenopus; D000096982:Urea Transporters
chemical_list: D026901:Membrane Transport Proteins; D011134:Polysaccharides; D011994:Recombinant Proteins; D012794:Sialic Acids; D000096982:Urea Transporters