Characterization of alpha 2,6-sialyltransferase cleavage by Alzheimer's beta -secretase (BACE1).
BACE1 is a membrane-bound aspartic protease that cleaves the amyloid precursor protein (APP) at the beta-secretase site, a critical step in the Alzheimer disease pathogenesis. We previously found that BACE1 also cleaved a membrane-bound sialyltransferase, ST6Gal I. By BACE1 overexpression in COS cells, the secretion of ST6Gal I markedly increased, and the amino terminus of the secreted ST6Gal I started at Glu(41). Here we report that BACE1-Fc chimera protein cleaved the A-ST6Gal I fusion protein, or ST6Gal I-derived peptide, between Leu(37) and Gln(38), suggesting that an initial cleavage product by BACE1 was three amino acids longer than the secreted ST6Gal I. The three amino acids, Gln(38)-Ala(39)-Lys(40), were found to be truncated by exopeptidase activity, which was detected in detergent extracts of Golgi-derived membrane fraction. These results suggest that ST6Gal I is cleaved initially between Leu(37) and Gln(38) by BACE1, and then the three-amino acid sequence at the NH(2) terminus is removed by exopeptidase(s) before secretion from the cells.
Kitazume
Shinobu
S
Glyco-chain Functions Laboratory, Supra-biomolecular System Group, Frontier Research System , Brain Science Institute, Institute of Physical and Chemical Research, RIKEN, Saitama 51-0198, Japan.
Tachida
Yuriko
Y
Oka
Ritsuko
R
Kotani
Norihiro
N
Ogawa
Kazuko
K
Suzuki
Minoru
M
Dohmae
Naoshi
N
Takio
Koji
K
Saido
Takaomi C
TC
Hashimoto
Yasuhiro
Y
D000544:Alzheimer Disease / Q000201:enzymology*; D053829:Amyloid Precursor Protein Secretases; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism*; D001665:Binding Sites; D019556:COS Cells; D010450:Endopeptidases; D020689:Exopeptidases / Q000378:metabolism; D006056:Golgi Apparatus / Q000201:enzymology; D006868:Hydrolysis; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D011993:Recombinant Fusion Proteins; D012799:Sialyltransferases / Q000378:metabolism*; D014162:Transfection; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase
D011993:Recombinant Fusion Proteins; D012799:Sialyltransferases; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D020689:Exopeptidases; D016282:Aspartic Acid Endopeptidases; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase