Involvement of proteases in glycosyltransferase secretion: Alzheimer's beta-secretase-dependent cleavage and a following processing by an aminopeptidase.
Alzheimer's beta-secretase (BACE1) cleaves amyloid precursor protein to produce amyloid beta-peptide, which is a crucial initiation process of the pathogenesis of Alzheimer's disease. We previously found that BACE1 also cleaves a membrane-bound sialyltransferase (ST6Gal I). Here we report that, when the protein A-ST6Gal I fusion protein, or ST6Gal I-derived peptide, was used as an in vitro substrate for BACE1, it cleaved the substrates between Leu(37) and Gln(38). However, a soluble form of ST6Gal I secreted from COS cells started from Glu(41), which was three amino acids shorter than the in vitro product. The results suggested that the BACE1 product was truncated by an aminopeptidase(s) before secretion. The aminopeptidase activity was successfully detected in detergent extracts of Golgi-membrane fraction. Taken together, we concluded that BACE1 initially cleaved ST6Gal I between Leu(37) and Gln(38), and the NH(2)-terminal three amino acids of the yielded product was further trimmed by the aminopeptidase.
Glyco-chain Functions Laboratory, Frontier Research System, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan. shinobuk@riken.jp
Shinobu
S
Kitazume
Minoru
M
Suzuki
Takaomi C
TC
Saido
Yasuhiro
Y
Hashimoto
D000409:Alanine / Q000737:chemistry; D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000737:chemistry*; D053829:Amyloid Precursor Protein Secretases; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism / Q000502:physiology*; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D010450:Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005973:Glutamine / Q000737:chemistry; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D007930:Leucine / Q000737:chemistry; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D010447:Peptide Hydrolases / Q000502:physiology*; D017434:Protein Structure, Tertiary; D012799:Sialyltransferases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase
D003902:Detergents; D005973:Glutamine; D012799:Sialyltransferases; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D010447:Peptide Hydrolases; D000626:Aminopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; D007930:Leucine; D000409:Alanine; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase