title: InsP₃receptors and Orai channels in pancreatic acinar cells: co-localization and its consequences.
abstract: Orai1 proteins have been recently identified as subunits of SOCE (store-operated Ca²⁺ entry) channels. In primary isolated PACs (pancreatic acinar cells), Orai1 showed remarkable co-localization and co-immunoprecipitation with all three subtypes of IP₃Rs (InsP₃ receptors). The co-localization between Orai1 and IP₃Rs was restricted to the apical part of PACs. Neither co-localization nor co-immunoprecipitation was affected by Ca²⁺ store depletion. Importantly we also characterized Orai1 in basal and lateral membranes of PACs. The basal and lateral membranes of PACs have been shown previously to accumulate STIM1 (stromal interaction molecule 1) puncta as a result of Ca²⁺ store depletion. We therefore conclude that these polarized secretory cells contain two pools of Orai1: an apical pool that interacts with IP₃Rs and a basolateral pool that interacts with STIM1 following the Ca²⁺ store depletion. Experiments on IP₃R knockout animals demonstrated that the apical Orai1 localization does not require IP₃Rs and that IP₃Rs are not necessary for the activation of SOCE. However, the InsP₃-releasing secretagogue ACh (acetylcholine) produced a negative modulatory effect on SOCE, suggesting that activated IP₃Rs could have an inhibitory effect on this Ca²⁺ entry mechanism.
authors.affiliation: Department of Cellular and Molecular Physiology, The University of Liverpool, Crown Street, Liverpool L69 3BX, UK.
authors.forename: Gyorgy
authors.initials: G
authors.lastname: Lur
authors.forename: Mark W
authors.initials: MW
authors.lastname: Sherwood
authors.forename: Etsuko
authors.initials: E
authors.lastname: Ebisui
authors.forename: Lee
authors.initials: L
authors.lastname: Haynes
authors.forename: Stefan
authors.initials: S
authors.lastname: Feske
authors.forename: Robert
authors.initials: R
authors.lastname: Sutton
authors.forename: Robert D
authors.initials: RD
authors.lastname: Burgoyne
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Mikoshiba
authors.forename: Ole H
authors.initials: OH
authors.lastname: Petersen
authors.forename: Alexei V
authors.initials: AV
authors.lastname: Tepikin
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000071740:ORAI1 Protein; D010179:Pancreas / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D046790:Pancreas, Exocrine / Q000737:chemistry* / Q000166:cytology* / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D000071740:ORAI1 Protein; C520430:Orai1 protein, mouse