Presenilin endoproteolysis mediated by an aspartyl protease activity pharmacologically distinct from gamma-secretase.
Presenilin (PS)-dependent gamma-secretase cleavage is the final proteolytic step in generating amyloid beta protein (A beta), a key peptide involved in the pathogenesis of Alzheimer's disease. PS undergoes endoproteolysis by an unidentified 'presenilinase' to generate the functional N-terminal and C-terminal fragment heterodimers (NTF/CTF) that may harbor the gamma-secretase active site. To better understand the relationship between presenilinase and gamma-secretase, we characterized the biochemical properties of presenilinase and compared them with those of gamma-secretase. Similar to gamma-secretase, presenilinase was most active at acidic pH 6.3. Aspartyl protease inhibitor pepstatin A blocked presenilinase activity with an IC50 of approximately 1 microM. Difluoroketone aspartyl protease transition state analogue MW167 was relatively selective for presenilinase (IC50 < 1 microM) over gamma-secretase (IC50-16 microM). Importantly, removing the transition state mimicking moiety simultaneously abolished both presenilinase and gamma-secretase inhibition, suggesting that presenilinase, like gamma-secretase, is an aspartyl protease. Interestingly, several of the most potent gamma-secretase inhibitors (IC50 = 0.3 or 20 nM) failed to block presenilinase activity. Although de novo generation of PS1 fragments coincided with production of A beta in vitro, blocking presenilinase activity without reducing pre-existing fragment levels permitted normal de novo generation of A beta and amyloid intracellular domain. Therefore, presenilinase has characteristics of an aspartyl protease, but this activity is distinct from gamma-secretase.
Campbell
William A
WA
Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
Reed
Megan L O
ML
Strahle
Jennifer
J
Wolfe
Michael S
MS
Xia
Weiming
W
D053829:Amyloid Precursor Protein Secretases; D016229:Amyloid beta-Peptides / Q000096:biosynthesis / Q000737:chemistry; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016466:CHO Cells; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D006224:Cricetinae; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D010450:Endopeptidases / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D010436:Pepstatins / Q000494:pharmacology; D010455:Peptides; D053764:Presenilin-1; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity
D016229:Amyloid beta-Peptides; D004791:Enzyme Inhibitors; C432344:MW167; D008565:Membrane Proteins; C508853:PSEN1 protein, human; D010436:Pepstatins; D010455:Peptides; D053764:Presenilin-1; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C475285:presenilinase, human; C509280:BACE1 protein, human; C031375:pepstatin