title: Ubiquilin 1 interacts with Orai1 to regulate calcium mobilization.
abstract: Store-operated calcium entry (SOCE) channels composed of Stim and Orai proteins play a critical role in diverse biological processes. Upon endoplasmic reticulum (ER)-mediated calcium (Ca(2+)) depletion, Stim proteins oligomerize with Orai to initiate Ca(2+) influx across the plasma membrane. The ubiquitin-like (UBL) and ubiquitin-associated (UBA) domains of ubiquilin 1 are involved in the degradation of presenilin and polyglutamine proteins. Through screening of Orai1 interaction partner(s) that might have an effect on SOCE, ubiquilin 1 was identified as a target of Orai1. However, the UBL and UBA domains of ubiquilin 1 were dispensable for this interaction. Additionally, ubiquilin 1 and Orai1 colocalized in the cytosolic compartment. Ubiquilin 1 increased the ubiquitination of Orai1, resulting in the formation of a high-molecular-weight form. MG132, a proteasome inhibitor, failed to block the degradation of Orai1, whereas bafilomycin A, a lysosome inhibitor, prevented Orai1 degradation. Confocal microscopy studies demonstrated that a fraction of Orai1 colocalized with ubiquilin 1 and the autophagosomal marker LC3. Because Orai1 is a constituent of SOCE, we determined the effect of ubiquilin 1 on Orai1-mediated Ca(2+) influx. As we expected, intracellular Ca(2+) mobilization, a process normally potentiated by Orai1, was downregulated by ubiquilin 1. Taken together, these findings suggest that ubiquilin 1 downregulates intracellular Ca(2+) mobilization and its downstream signaling by promoting the ubiquitination and lysosomal degradation of Orai1.
authors.affiliation: Division of Biochemistry, Chungbuk National University, Cheongju, 361-763, Korea.
authors.forename: Jeong-Eun
authors.initials: JE
authors.lastname: Lee
authors.forename: In-Sook
authors.initials: IS
authors.lastname: Jeon
authors.forename: Na-Eun
authors.initials: NE
authors.lastname: Han
authors.forename: Hye-Jin
authors.initials: HJ
authors.lastname: Song
authors.forename: Eung-Gook
authors.initials: EG
authors.lastname: Kim
authors.forename: Jae-Woon
authors.initials: JW
authors.lastname: Choi
authors.forename: Ki-Duk
authors.initials: KD
authors.lastname: Song
authors.forename: Hak-Kyo
authors.initials: HK
authors.lastname: Lee
authors.forename: Joong-Kook
authors.initials: JK
authors.lastname: Choi
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000071183:Autophagy-Related Proteins; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D007976:Leupeptins / Q000494:pharmacology; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D018942:Macrolides / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D000071740:ORAI1 Protein; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D015398:Signal Transduction; D000071737:Stromal Interaction Molecule 1; D020798:Two-Hybrid System Techniques; D054875:Ubiquitination
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000071183:Autophagy-Related Proteins; D015220:Calcium Channels; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; D007976:Leupeptins; D018942:Macrolides; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; C107792:UBQLN1 protein, human; C057620:bafilomycin A; D046988:Proteasome Endopeptidase Complex; D006180:Proton-Translocating ATPases; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D002118:Calcium