Ubiquilin 1 interacts with Orai1 to regulate calcium mobilization

• Published in: Molecules and cells Vol. 35; no. 1; pp. 41 - 46
• Main Authors: Lee, Jeong-Eun, Jeon, In-Sook, Han, Na-Eun, Song, Hye-Jin, Kim, Eung-Gook, Choi, Jae-Woon, Song, Ki-Duk, Lee, Hak-Kyo, Choi, Joong-Kook
• Format: Journal Article
• Language: English
• Published: Springer Korean Society for Molecular and Cellular Biology 01.01.2013; Korea Society for Molecular and Cellular Biology; 한국분자세포생물학회
• Subjects: Adaptor Proteins, Signal Transducing; Autophagy-Related Proteins; Biochemistry; Biomedical and Life Sciences; Biomedicine; Biotechnology; Blotting, Western; Calcium - metabolism; Calcium Channels - genetics; Calcium Channels - metabolism; Calcium Signaling; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell Biology; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Cysteine Proteinase Inhibitors - pharmacology; Cytosol - drug effects; Cytosol - metabolism; Enzyme Inhibitors - pharmacology; HEK293 Cells; HeLa Cells; Humans; Immunoprecipitation; Leupeptins - pharmacology; Life Sciences; Lysosomes - drug effects; Lysosomes - metabolism; Macrolides - pharmacology; Membrane Proteins - genetics; Membrane Proteins - metabolism; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; ORAI1 Protein; Phagosomes - drug effects; Phagosomes - metabolism; Plasmids - genetics; Proteasome Endopeptidase Complex - chemistry; Proteasome Endopeptidase Complex - metabolism; Proton-Translocating ATPases - antagonists & inhibitors; Research Article; Signal Transduction; Stromal Interaction Molecule 1; Two-Hybrid System Techniques; Ubiquitination; 생물학; Orai1; store-operated calcium entry (SOCE); Stim1; calcium mobilization; ubiquilin
• ISSN: 1016-8478; 0219-1032
• DOI: 10.1007/s10059-013-2268-7

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.