title: Functional assembly and purinergic activation of bestrophins.
abstract: Proteins of the bestrophin family produce Ca(2+)-activated Cl(-) currents and regulate voltage-gated Ca(2+) channels. Bestrophin 1 was first identified in the retinal pigment epithelium. Four human paralogs (hBest1-hBest4) exist, and for some bestrophins, dimeric and heterotetrameric structures have been proposed. Here, we demonstrate that hBest1-hBest4 induce Cl(-) conductances of different amplitudes when expressed in HEK293 cells and when activated through purinergic stimulation. hBest1 mutants that are known to cause autosomal dominant macular dystrophy (Best disease) did not produce a Cl(-) current. Bestrophins were colocalized and showed molecular and functional interaction in HEK293 cells, overexpressing hBest1 and hBest2 or hBest4. Interaction was confirmed in airway epithelial cells coexpressing endogenous bestrophins. A fraction of hBest2 and hBest4 was expressed in the membrane, while most of hBest1 was found in the endoplasmic reticulum. Nevertheless, hBest1 has a clear role for the adenosine triphosphate (ATP; or uridine triphosphate)-induced Cl(-) current in both HEK293 and Calu-3 cells. Since native epithelial tissues typically express several bestrophin paralogs, these proteins may exist as heterooligomeric structures.
authors.affiliation: Institut für Physiologie, Universität Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
authors.forename: Vladimir M
authors.initials: VM
authors.lastname: Milenkovic
authors.forename: René Barro
authors.initials: RB
authors.lastname: Soria
authors.forename: Fadi
authors.initials: F
authors.lastname: Aldehni
authors.forename: Rainer
authors.initials: R
authors.lastname: Schreiber
authors.forename: Karl
authors.initials: K
authors.lastname: Kunzelmann
mesh_terms: D000075002:Bestrophins; D020013:Calcium Signaling / Q000502:physiology; D002460:Cell Line; D018118:Chloride Channels / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D005136:Eye Proteins / Q000502:physiology*; D006801:Humans; D007668:Kidney / Q000166:cytology; D018408:Patch-Clamp Techniques; D055503:Protein Multimerization; D055213:Retinal Pigment Epithelium / Q000502:physiology
chemical_list: C113133:BEST1 protein, human; C465970:BEST2 protein, human; C465971:BEST4 protein, human; D000075002:Bestrophins; D018118:Chloride Channels; D002712:Chlorides; D005136:Eye Proteins