In:
Science Signaling, American Association for the Advancement of Science (AAAS), Vol. 9, No. 418 ( 2016-03-08)
Abstract:
N-glycosylation of cell surface proteins affects protein function, stability, and interaction with other proteins. Orai channels, which mediate store-operated Ca 2+ entry (SOCE), are composed of N-glycosylated subunits. Upon activation by Ca 2+ sensor proteins (stromal interaction molecules STIM1 or STIM2) in the endoplasmic reticulum, Orai Ca 2+ channels in the plasma membrane mediate Ca 2+ influx. Lectins are carbohydrate-binding proteins, and Siglecs are a family of sialic acid–binding lectins with immunoglobulin-like repeats. Using Western blot analysis and lectin-binding assays from various primary human cells and cancer cell lines, we found that glycosylation of Orai1 is cell type–specific. Ca 2+ imaging experiments and patch-clamp experiments revealed that mutation of the only glycosylation site of Orai1 (Orai1N223A) enhanced SOCE in Jurkat T cells. Knockdown of the sialyltransferase ST6GAL1 reduced α-2,6–linked sialic acids in the glycan structure of Orai1 and was associated with increased Ca 2+ entry in Jurkat T cells. In human mast cells, inhibition of sialyl sulfation altered the N -glycan of Orai1 (and other proteins) and increased SOCE. These data suggest that cell type–specific glycosylation influences the interaction of Orai1 with specific lectins, such as Siglecs, which then attenuates SOCE. In summary, the glycosylation state of Orai1 influences SOCE-mediated Ca 2+ signaling and, thus, may contribute to pathophysiological Ca 2+ signaling observed in immune disease and cancer.
Type of Medium:
Online Resource
ISSN:
1945-0877
,
1937-9145
DOI:
10.1126/scisignal.aaa9913
Language:
English
Publisher:
American Association for the Advancement of Science (AAAS)
Publication Date:
2016
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