The disulphide bonds in the catalytic domain of BACE are critical but not essential for amyloid precursor protein processing activity.
beta-Site APP-cleaving enzyme (BACE) initiates the processing of the amyloid precursor protein (APP) leading to the generation of beta-amyloid, the main component of Alzheimer's disease senile plaques. BACE (Asp2, memapsin 2) is a type I transmembrane aspartic protease responsible for the beta-secretase cleavage of APP producing a soluble form of the ectodomain (sAPPbeta) and the membrane-bound, carboxy-terminal intermediates C99 and C89. BACE maturation involves cysteine bridge formation, N -glycosylation and propeptide removal. We investigated variants of BACE in which the disulphide bonds of the catalytic domain spanning between Cys216/Cys420, Cys278/Cys443 and Cys330/Cys380 were removed by mutagenesis. When transfected in cultured cells, these mutants showed impaired maturation. Nevertheless, a fraction of mutated protein retained both the competence to mature as well as the activity to process APP. For the generation of a functional enzyme the conserved Cys330/Cys380 bond was the most critical, whereas the two bonds between Cys216/Cys420 and Cys278/Cys443, which are typical for the membrane-bound BACE, appeared to be less important.
Fischer
Frauke
F
Nervous System, Novartis Pharma AG, Basel, Switzerland. Institute for Research in Biomedicine, Bellinzona, Switzerland.
Molinari
Maurizio
M
Bodendorf
Ursula
U
Paganetti
Paolo
P
D000544:Alzheimer Disease / Q000201:enzymology; D053829:Amyloid Precursor Protein Secretases; D016564:Amyloid beta-Protein Precursor / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020126:Brefeldin A / Q000494:pharmacology; D019556:COS Cells / Q000378:metabolism; D020134:Catalytic Domain / Q000502:physiology*; D002460:Cell Line; D004220:Disulfides / Q000737:chemistry*; D010450:Endopeptidases; D004789:Enzyme Activation / Q000187:drug effects; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D006596:Hexosaminidases / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D017510:Protein Folding; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D021381:Protein Transport; D013329:Structure-Activity Relationship; D014162:Transfection
D016564:Amyloid beta-Protein Precursor; D004220:Disulfides; D011500:Protein Synthesis Inhibitors; D020126:Brefeldin A; D006596:Hexosaminidases; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509284:BACE2 protein, human; C509280:BACE1 protein, human