Asian Science Citation Index is committed to provide an authoritative, trusted and significant information by the coverage of the most important and influential journals to meet the needs of the global scientific community.  
ASCI Database
308-Lasani Town,
Sargodha Road,
Faisalabad, Pakistan
Fax: +92-41-8815544
Contact Via Web
Suggest a Journal
 
Articles by N Kawasaki
Total Records ( 2 ) for N Kawasaki
  D Hu , Y Kamiya , K Totani , D Kamiya , N Kawasaki , D Yamaguchi , I Matsuo , N Matsumoto , Y Ito , K Kato and K. Yamamoto
 

Glucosidase II (GII) is a glycan-processing enzyme that trims two 1,3-linked glucose residues from N-glycan on newly synthesized glycoproteins. Trimming of the first 1,3-linked glucose from Glc2Man9GlcNAc2 (G2M9) is important for a glycoprotein to interact with calnexin/calreticulin (CNX/CRT), and cleavage of the innermost glucose from Glc1Man9GlcNAc2 (G1M9) sets glycoproteins free from the CNX/CRT cycle and allows them to proceed to the Golgi apparatus. GII is a heterodimeric complex consisting of a catalytic subunit (GII) and a tightly associated β subunit (GIIβ) that contains a mannose 6-phosphate receptor homology (MRH) domain. A recent study has suggested a possible involvement of the MRH domain of GIIβ (GIIβ-MRH) in the glucose trimming process via its putative sugar-binding activity. However, it remains unknown whether GIIβ-MRH possesses sugar-binding activity and, if so, what role this activity plays in the function of GII. Here, we demonstrate that human GIIβ-MRH binds to high-mannose-type glycans. Frontal affinity chromatography revealed that GIIβ-MRH binds most strongly to the glycans with the 1,2-linked mannobiose structure. GII with the mutant GIIβ that lost the sugar-binding activity of GIIβ-MRH hydrolyzes p-nitrophenyl--glucopyranoside, but the capacity to remove glucose residues from G1M9 and G2M9 is significantly decreased. Our results clearly demonstrate the capacity of the GIIβ-MRH to bind high-mannose-type glycans and its importance in efficient glucose trimming of N-glycans.

  K Mikami , D Yamaguchi , H Tateno , D Hu , S. Y Qin , N Kawasaki , M Yamada , N Matsumoto , J Hirabayashi , Y Ito and K. Yamamoto
 

Misfolded glycoproteins are translocated from the endoplasmic reticulum (ER) into the cytoplasm for proteasome-mediated degradation. OS-9 protein is thought to participate in ER-associated glycoprotein degradation (ERAD). The recombinant biotinylated mannose 6-phosphate receptor homology (MRH) domain of human OS-9 (OS-9MRH) together with six kinds of mutated OS-9MRH were prepared and mixed with R-phycoerythrin (PE)-labeled streptavidin to form tetramers (OS-9MRH-SA). The PE-labeled OS-9MRH-SA bound to HeLaS3 cells in a metal ion-independent manner through amino acid residues homologous to those participating in sugar binding of the cation-dependent mannose 6-phosphate receptor, and this binding was greatly increased by swainsonine, deoxymannojirimycin, or kifunensine treatment. N-Acetylglucosaminyltransferase I-deficient Lec1 cells, but not Lec2 or Lec8 cells, were also strongly bound by the tetramer. OS-9MRH-SA binding to the cells was strongly inhibited by Man1,6(Man1,3)Man1,6(Man1,3)Man and Man1,6Man. To further determine the specificity of native ligands for OS-9MRH, frontal affinity chromatography was performed using a wide variety of 92 different oligosaccharides. We found that several N-glycans containing terminal 1,6-linked mannose in the Man1,6(Man1,3)Man1,6(Man1,3)Man structure were good ligands for OS-9MRH, having Ka values of approximately 104 M–1 and that trimming of either an 1,6-linked mannose from the C-arm or an 1,3-linked mannose from the B-arm abrogated binding to OS-9MRH. An immunoprecipitation experiment demonstrated that the 1-antitrypsin variant nullHong Kong, but not wild-type 1-antitrypsin, selectively interacted with OS-9 in the cells in a sugar-dependent manner. These results suggest that trimming of the outermost 1,2-linked mannose on the C-arm is a critical process for misfolded proteins to enter ERAD.

 
 
 
Copyright   |   Desclaimer   |    Privacy Policy   |   Browsers   |   Accessibility