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新着情報 |
博士課程１年木塚君の研究成果がJ. Biol. Chem.に発表されます。（2006、4)
Physical
and functional association of glucuronyltransferases and sulfotransferase
involved in HNK-1 biosynthesis
Yasuhiko Kizuka, Takahiro Matsui, Hiromu Takematsu, Yasunori
Kozutsumi, Toshisuke Kawasaki, and Shogo Oka
(J. Biol. Chem. 281, 13644-13651, 2006.) |
| HNK-1 carbohydrate
expressed predominantly in the nervous system is considered
to be involved in cell migration, recognition, adhesion and
synaptic plasticity. HNK-1 carbohydrate has a unique structure
comprising a sulfated trisaccharide (HSO3-3GlcAb1-3Galb1-4GlcNAc-)
and is sequentially biosynthesized by one of two glucuronyltransferases
(GlcAT-P or GlcAT-S) and a sulfotransferase (HNK-1ST). Considering
that almost all the HNK-1 carbohydrate structures in the nervous
system so far determined are sulfated, we hypothesized that
GlcAT-P or GlcAT-S functionally associates with HNK-1ST, which
results in efficient sequential biosynthesis of HNK-1 carbohydrate.
In this study, we demonstrated that both GlcAT-P and GlcAT-S
were co-immunoprecipitated with HNK-1ST with a transient expression
system in CHO cells. Immunofluorescence staining revealed
that these enzymes are mainly co-localized in the Golgi apparatus.
In order to determine which domain is involved in this interaction,
we prepared the C-terminal catalytic domains of GlcAT-P, GlcAT-S
and HNK-1ST, and then performed pull-down assays with the
purified enzymes. As a result, we obtained evidence that mutual
catalytic domains of GlcAT-P or S and HNK-1ST are important
and sufficient for formation of an enzyme complex. With an
in vitro assay system, the activity of HNK-1ST increased about
two-fold in the presence of GlcAT-P or GlcAT-S compared to
that in its absence. These results suggest that the function
of this enzyme complex is relevant to the efficient sequential
biosynthesis of HNK-1 carbohydrate. |
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