title: Isoforms, expression, glycosylation, and tissue distribution of CTL2/SLC44A2.
abstract: Antibodies to the solute carrier protein, CTL2/SLC44A2, cause hearing loss in animals, are frequently found in autoimmune hearing loss patients, and are implicated in transfusion-related acute lung injury. We cloned a novel CTL2/SLC44A2 isoform (CTL2 P1) from inner ear and identified an alternate upstream promoter and exon 1a encoding a protein of 704 amino acids which differs in the first 10-12 amino acids from the known exon 1b isoform (CTL2 P2; 706 amino acids). The expression of these CTL2/SLC44A2 isoforms, their posttranslational modifications in tissues and their localization in HEK293 cells expressing rHuCTL2/SLC44A2 were assessed. P1 and P2 isoforms with differing glycosylation are variably expressed in cochlea, tongue, heart, colon, lung, kidney, liver and spleen suggesting tissue specific differences that may influence function in each tissue. Because antibodies to CTL2/SLC44A2 have serious pathologic consequences, it is important to understand its distribution and modifications. Heterologous expression in X. laevis oocytes shows that while human CTL2-P1 does not transport choline, human CTL2-P2 exhibits detectable choline transport activity.
authors.affiliation: Kresge Hearing Research Institute, Department of Otolaryngology/Head and Neck Surgery, The University of Michigan, 1150 West Medical Center Drive, Room 5311 Medical Science I, Ann Arbor, MI 48109-5516, USA.
authors.forename: P K
authors.initials: PK
authors.lastname: Kommareddi
authors.forename: T S
authors.initials: TS
authors.lastname: Nair
authors.forename: L V
authors.initials: LV
authors.lastname: Thang
authors.forename: M M
authors.initials: MM
authors.lastname: Galano
authors.forename: E
authors.initials: E
authors.lastname: Babu
authors.forename: V
authors.initials: V
authors.lastname: Ganapathy
authors.forename: T
authors.initials: T
authors.lastname: Kanazawa
authors.forename: J B
authors.initials: JB
authors.lastname: McHugh
authors.forename: T E
authors.initials: TE
authors.lastname: Carey
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001327:Autoimmune Diseases; D002460:Cell Line; D003198:Computer Simulation; D007758:Ear, Inner / Q000378:metabolism; D006031:Glycosylation; D006168:Guinea Pigs; D034381:Hearing Loss; D006801:Humans; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D027701:Organic Cation Transport Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020033:Protein Isoforms; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014018:Tissue Distribution
chemical_list: D015703:Antigens, CD; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D027701:Organic Cation Transport Proteins; D020033:Protein Isoforms; C510732:SLC44A1 protein, human; C484524:SLC44A2 protein, human