期刊
JOURNAL OF IMMUNOLOGY
卷 171, 期 8, 页码 4062-4072出版社
AMER ASSOC IMMUNOLOGISTS
DOI: 10.4049/jimmunol.171.8.4062
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- NCI NIH HHS [CA81776, CA54464] Funding Source: Medline
- NIAID NIH HHS [AI45900] Funding Source: Medline
CD81 is a widely expressed tetraspanin that associates in B cells with CD19 in the CD19-CD21-CD81 signaling complex. CD81 is necessary for normal CD19 expression; cd81(-/-) B cells express lower levels of CD19, especially cd81(-/-) small pre-BII cells, which are almost devoid of surface CD19. The dependence of CD19 expression on CD81 is specific to this particular tetraspanin since cd9(-/-) B cells express normal levels of CD19. Furthermore, expression of human CD81 in mouse cd81(-/-) B cells restored surface CD19 to normal levels. Quantitative analysis of CD19 mRNA demonstrated normal levels, even in cd81(-/-) pre-BII cells. Analysis of CD19 at the protein level identified two CD19 glycoforms in both wild-type and cd81(-/-) B cells. The higher Mr glycoform is significantly reduced in cd81(-/-) B cells and is endoglycosidase H (endo-H) resistant. In contrast, the low Mr glycoform is comparably expressed in cd81(-/-) and in wild-type B cells and is endo-H sensitive. Because endo-H sensitivity is tightly correlated with endoplasmic reticulum localization, we suggest that the dependency of CD19 expression on CD81 occurs in a postendoplasmic reticulum compartment where CD81 is necessary for normal trafficking or for surface membrane stability of CD19.
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