Summary

The MGAT5B gene encodes a beta-1,6-N-acetylglucosaminyltransferase (EC 2.4.1.155) that functions in the synthesis of complex cell surface N-glycans (Kaneko et al., 2003 [PubMed 14623122]).[supplied by OMIM]

Function

Glycosyltransferase that acts on alpha-linked mannose of N-glycans and O-mannosyl glycans. Catalyzes the transfer of N-acetylglucosamine (GlcNAc) to the beta 1-6 linkage of the mannose residue of GlcNAcbeta1,2-Manalpha on both the alpha1,3- and alpha1,6-linked mannose arms in the core structure of N-glycan. Also acts on the GlcNAcbeta1,2-Manalpha1-Ser/Thr moiety, forming a 2,6-branched structure in brain O-mannosyl glycan.

Plays an active role in modulating integrin and laminin-dependent adhesion and migration of neuronal cells via its activity in the O-mannosyl glycan pathway.

Ref.1   Ref.2   Ref.6   Ref.7   Ref.8  

Disease relevance of MGAT5B

• The ability of GnT-VB to regulate cell-matrix interactions was initially investigated using the rat pheochromocytoma PC12 neurite outgrowth model [1].

High impact information on MGAT5B

• Here we examined the issue of whether GnT-IX is able to act on the same sequence of the GlcNAcbeta1,2-Manalpha in O-mannosyl glycan [2].
• Furthermore, incorporation of an additional GlcNAc residue into a synthetic mannosyl peptide Ac-Ala-Ala-Pro-Thr(Man)-Pro-Val-Ala-Ala-Pro-NH(2) by GnT-IX was only observed in the presence of POMGnT1 [2].
• Consistent with the above data, GnT-IX generated a new product which was identified as GlcNAcbeta1,2-(GlcNAcbeta1,6-)Manalpha1-Ser-PAES by mass spectrometry and (1)H NMR [2].
• Namely, the new GnT (designated as GnT-IX) has beta1,6GnT activity not only to the alpha1,6-linked mannose arm but also to the alpha1,3-linked mannose arm of N-glycan, forming a unique structure that has not been reported to date [3].
• The glycosyltransferase GnT-Vb, also known as GnT-IX, is expressed abundantly in the brain and testis and is proposed to be the enzyme that branches O-mannosyl-linked glycans [4].

Biological context of MGAT5B

• We report here the cloning and characterization of a human cDNA encoding a distinct enzyme with related substrate specificity, termed GnT-VB, which is predicted to have 53% similarity to the original amino acid sequence of GnT-V(A) [5].

Anatomical context of MGAT5B

• Real-time polymerase chain reaction results showed that GnT-VB mRNA was highly expressed in brain and testis, with lesser levels in other tissues, while human GnT-VA showed a more general expression, but with low levels in brain and no expression in skeletal muscle [5].
• These results demonstrate that GnT-VB expression can modulate the rate of neurite outgrowth by affecting beta1 integrin-ECM interaction [1].

Associations of MGAT5B with chemical compounds

• Neurite outgrowth induced by manganese-dependent activation of beta1 integrin on collagen and laminin substrates, however, showed a significant increase in neurite length for the PC12/GnT-VB cells, compared with control cells, suggesting that the enhancement is most likely mediated by alteration of beta1 integrin-ECM interaction by GnT-VB [1].

Other interactions of MGAT5B

• N-acetylglucosaminyltransferase VB (GnT-VB, -IX) is a newly discovered glycosyltransferase expressed exclusively in high levels in neuronal tissue during early development [1].

Analytical, diagnostic and therapeutic context of MGAT5B

• Northern blot analysis showed that the GnT-IX gene is exclusively expressed in the brain, whereas the GnT-V gene is expressed ubiquitously [3].
• Molecular cloning and characterization of human GnT-IX, a novel beta1,6-N-acetylglucosaminyltransferase that is specifically expressed in the brain [3].

References