title: A variant of the Ca2+-activated Cl channel Best3 is expressed in mouse exocrine glands.
abstract: Fluid secretion by exocrine glands requires the activation of an apical Ca2+-dependent Cl channel, the molecular identity of which is unknown. We found that mouse exocrine glands expressed an alternately spliced variant of Best3, a member of the Bestrophin (Vmd2) Ca2+-activated Cl channel gene family, whereas the heart expressed full-length Best3. The spliced transcript lacked exons 2, 3 and 6 (Best3-Delta2,3,6) and is predicted to generate an in-frame protein missing the entire cytoplasmic N terminus, the initial two transmembrane domains and part of the first intracellular loop. In addition to exocrine glands, the Best3-Delta2,3,6 splice variant transcript was detected in lung, testis and kidney. The parotid gland and heart expressed proteins of the predicted size for Best3-Delta2,3,6 and full-length Best3, respectively, that targeted to the plasma membrane in HEK293 cells. HEK293 cells expressing Best3 displayed Ca2+-dependent Cl(-) currents that were sensitive to the Cl channel blocker DIDS. In contrast, no Ca2+-dependent Cl(-) currents were detected in cells expressing Best3-Delta2,3,6. Cotransfection of Best3-Delta2,3,6 with Best3 or Best2 (also expressed in salivary gland acinar cells) had no significant effects on the currents generated by either of these Ca2+-dependent Cl channels. Our results demonstrate that exocrine glands express a unique splice variant of Best3. Nevertheless, Best3-Delta2,3,6 does not produce Ca2+-dependent Cl(-) currents, nor does it regulate the activity of Best2 or the full-length Best3 channel.
authors.affiliation: Center for Oral Biology, Medical Center, University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave., Box 611, Rochester, NY 14642, USA.
authors.forename: Alaka
authors.initials: A
authors.lastname: Srivastava
authors.forename: Victor G
authors.initials: VG
authors.lastname: Romanenko
authors.forename: Mireya
authors.initials: M
authors.lastname: Gonzalez-Begne
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Catalán
authors.forename: James E
authors.initials: JE
authors.lastname: Melvin
mesh_terms: D017398:Alternative Splicing / Q000502:physiology*; D000818:Animals; D000075002:Bestrophins; D002460:Cell Line; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D018118:Chloride Channels / Q000096:biosynthesis* / Q000235:genetics; D005088:Exocrine Glands / Q000378:metabolism*; D005136:Eye Proteins / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D007473:Ion Channels; D051379:Mice; D009928:Organ Specificity / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology
chemical_list: C491856:Best1 protein, mouse; C497463:Best2 protein, mouse; D000075002:Bestrophins; D018118:Chloride Channels; D005136:Eye Proteins; D007473:Ion Channels