title: The presence of bestrophin-1 modulates the Ca2+ recruitment from Ca2+ stores in the ER.
abstract: Bestrophin-1, mainly analyzed in overexpression experiments, functions as Ca(2+)-dependent Cl(-) channel. Analysis of endogenously expressed bestrophin-1 suggested an influence on intracellular Ca(2+). The aim of the study is to analyze the influence of endogenously expressed bestrophin-1 on Ca(2+) homeostasis. Primary cultures of retinal pigment epithelial (RPE) cells were established from wild-type and bestrophin-1-deficient mice. Intracellular free Ca(2+) ([Ca(2+)](i)) was recorded by Ca(2+) imaging; through immunocytochemistry and differential centrifugation, subcellular localization of bestrophin-1 was analyzed. RPE cells of bestrophin-1-deficient mice showed higher levels of resting [Ca(2+)](i) than cells from wild-type mice. In cells from knockout mice and wild-type mice, ATP led to increases in [Ca(2+)](i) subsequent to phospholipase C activation. ATP-induced Ca(2+) in bestrophin-1-deficient mice rose faster and decayed slower. In cells from wild-type mice, ATP led to [Ca(2+)](i) increase via depletion of Ca(2+) from thapsigargin-sensitive stores. In cells from bestrophin-1-deficient mice, ATP-dependent increase in [Ca(2+)](i) resulted in 40% of cells from depletion of bafilomycin-sensitive and in 60% from thapsigargin-sensitive Ca(2+) stores. After differential centrifugation, bestrophin-1 was found in fractions enriched of ClC-3 Cl channel and myosin-7A. Co-localization analysis of bestrophin-1, with beta-catenin or pan-cadherin, in fresh sections of porcine retina, revealed bestrophin-1 in the basolateral membrane. A portion of endogenously expressed bestrophin-1,localized in the endoplasmic reticulum, influenced uptake of Ca(2+) into Ca(2+) stores. Therefore, bestrophin-1 possibly conducts Cl(-) as counter ion for Ca(2+) uptake into cytosolic Ca(2+) stores.
authors.affiliation: Experimental Eye Research, Eye Hospital, University Hospital Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Rudgar
authors.initials: R
authors.lastname: Neussert
authors.forename: Claudia
authors.initials: C
authors.lastname: Müller
authors.forename: Vladimir M
authors.initials: VM
authors.lastname: Milenkovic
authors.forename: Olaf
authors.initials: O
authors.lastname: Strauss
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000075002:Bestrophins; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D002712:Chlorides / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D006706:Homeostasis; D007150:Immunohistochemistry; D007473:Ion Channels; D018942:Macrolides / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D055213:Retinal Pigment Epithelium / Q000187:drug effects / Q000378:metabolism*; D013552:Swine; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: C491856:Best1 protein, mouse; D000075002:Bestrophins; D002712:Chlorides; D004791:Enzyme Inhibitors; D005136:Eye Proteins; D007473:Ion Channels; D018942:Macrolides; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D010738:Type C Phospholipases; D000252:Calcium-Transporting ATPases; D002118:Calcium
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