BACE2 functions as an alternative alpha-secretase in cells.
BACE1 and BACE2 define a new subfamily of membrane-anchored aspartyl proteases. Both endoproteases share similar structural organization including a prodomain, a catalytic domain formed via DTG and DSG active site motifs, a single transmembrane domain, and a short C-terminal tail. BACE1 has been identified as the Alzheimer's beta-secretase, whereas BACE2 was mapped to the Down's critical region of human chromosome 21. Herein we show that purified BACE2 can be autoactivated in vitro. Purified BACE2 cleaves human amyloid precursor protein (APP) sequences at the beta-secretase site, and near the alpha-secretase site, mainly at A beta-Phe(20)--Ala(21) and also at A beta-Phe(19)--Phe(20). Alternatively, in cells BACE2 has a limited effect on the beta-secretase site but efficiently cleaves the sequences near the alpha-secretase site. The in vitro specificity of APP processing by BACE2 is distinct from that observed in cells. BACE2 localizes in the endoplasmic reticulum, Golgi, trans-Golgi network, endosomes, and plasma membrane, and its cellular localization patterns depend on the presence of its transmembrane domain. BACE2 chimeras that increase localization of BACE2 in the trans-Golgi network do not change its APP processing patterns. Thus, BACE2 can be distinguished from BACE1 on the basis of autoprocessing of the prosegment, APP processing specificity, and subcellular localization patterns.
Yan
R
R
Department of Cell and Molecular Biology, Pharmacia Corporation, Kalamazoo, Michigan 49007, USA. ryan@pharmacia.com
Munzner
J B
JB
Shuck
M E
ME
Bienkowski
M J
MJ
D000409:Alanine / Q000737:chemistry; D020816:Amino Acid Motifs; D053829:Amyloid Precursor Protein Secretases; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism; D001665:Binding Sites; D015153:Blotting, Western; D002462:Cell Membrane / Q000201:enzymology; D002891:Chromosomes, Human, Pair 21; D010450:Endopeptidases / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000201:enzymology; D011992:Endosomes / Q000201:enzymology; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006056:Golgi Apparatus / Q000201:enzymology; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008856:Microscopy, Fluorescence; D016376:Oligonucleotides, Antisense / Q000378:metabolism; D010649:Phenylalanine / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D013997:Time Factors; D014162:Transfection; D021601:trans-Golgi Network / Q000201:enzymology
D016564:Amyloid beta-Protein Precursor; D006023:Glycoproteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D011994:Recombinant Proteins; D049452:Green Fluorescent Proteins; D010649:Phenylalanine; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509284:BACE2 protein, human; C509280:BACE1 protein, human; D000409:Alanine