In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 107, No. 26 ( 2010-06-29), p. 11900-11905
Abstract:
In a previous study, we demonstrated that β1,3- N -acetylglucosaminyltransferase 5 ( B3gnt5 ) is a lactotriaosylceramide (Lc 3 Cer) synthase that synthesizes a precursor structure for lacto/neolacto-series glycosphingolipids (GSLs) in in vitro experiments. Here, we generated B3gnt5 -deficient ( B3gnt5 −/− ) mice to investigate the in vivo biological functions of lacto/neolacto-series GSLs. In biochemical analyses, lacto/neolacto-series GSLs were confirmed to be absent and no Lc 3 Cer synthase activity was detected in the tissues of these mice. These results demonstrate that β3GnT5 is the sole enzyme synthesizing Lc 3 Cer in vivo. Ganglioside GM1, known as a glycosphingolipid-enriched microdomain (GEM) marker, was found to be up-regulated in B3gnt5 −/− B cells by flow cytometry and fluorescence microscopy. However, no difference in the amount of GM1 was observed by TLC-immunoblotting analysis. The GEM-stained puncta on the surface of B3gnt5 −/− resting B cells were brighter and larger than those of WT cells. These results suggest that structural alteration of GEM occurs in B3gnt5 −/− B cells. We next examined whether BCR signaling-related proteins, such as BCR, CD19, and the signaling molecule Lyn, had moved into or out of the GEM fraction. In B3gnt5 −/− B cells, these molecules were enriched in the GEM fraction or adjacent fraction. Moreover, B3gnt5 −/− B cells were more sensitive to the induction of intracellular phosphorylation signals on BCR stimulation and proliferated more vigorously than WT B cells. Together, these results suggest that lacto/neolacto-series GSLs play an important role in clustering of GEMs and tether-specific proteins, such as BCR, CD19, and related signaling molecules to the GEMs.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.0914298107
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2010
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
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