Ming-Chih Crouthamel

Publications (17)64.08 Total impact

• Article: SAR of tertiary carbinamine derived BACE1 inhibitors: role of aspartate ligand amine pKa in enzyme inhibition.

  Hemaka A Rajapakse, Philippe G Nantermet, Harold G Selnick, James C Barrow, Georgia B McGaughey, Sanjeev Munshi, Stacey R Lindsley, Mary Beth Young, Phung L Ngo, M Katherine Holloway, [......], Beth Pietrak, Ming-Chih Crouthamel, Katherine Tugusheva, Qian Huang, Min Xu, Adam J Simon, Lawrence Kuo, Daria J Hazuda, Samuel Graham, Joseph P Vacca
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  ABSTRACT: The optimization of tertiary carbinamine derived inhibitors of BACE1 from its discovery as an unstable lead to low nanomolar cell active compounds is described. Five-membered heterocycles are reported as stable and potency enhancing linkers. In the course of this work, we have discovered a clear trend where the activity of inhibitors at a given assay pH is dependent on pK(a) of the amino group that interacts directly with the catalytic aspartates. The potency of compounds as inhibitors of Alphabeta production in a cell culture assay correlated much better with BACE1 enzyme potency measured at pH 7.5 than at pH 4.5.
  Bioorganic & medicinal chemistry letters 02/2010; 20(6):1885-9. · 2.65 Impact Factor
• Article: First demonstration of cerebrospinal fluid and plasma A beta lowering with oral administration of a beta-site amyloid precursor protein-cleaving enzyme 1 inhibitor in nonhuman primates.

  Sethu Sankaranarayanan, Marie A Holahan, Dennis Colussi, Ming-Chih Crouthamel, Viswanath Devanarayan, Joan Ellis, Amy Espeseth, Adam T Gates, Samuel L Graham, Allison R Gregro, [......], Matthew G Stanton, John Swestock, Katherine Tugusheva, Keala X Tyler, Joseph P Vacca, Jacky Wong, Guoxin Wu, Min Xu, Jacquelynn J Cook, Adam J Simon
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  ABSTRACT: beta-Site amyloid precursor protein (APP)-cleaving enzyme (BACE) 1 cleavage of amyloid precursor protein is an essential step in the generation of the potentially neurotoxic and amyloidogenic A beta 42 peptides in Alzheimer's disease. Although previous mouse studies have shown brain A beta lowering after BACE1 inhibition, extension of such studies to nonhuman primates or man was precluded by poor potency, brain penetration, and pharmacokinetics of available inhibitors. In this study, a novel tertiary carbinamine BACE1 inhibitor, tertiary carbinamine (TC)-1, was assessed in a unique cisterna magna ported rhesus monkey model, where the temporal dynamics of A beta in cerebrospinal fluid (CSF) and plasma could be evaluated. TC-1, a potent inhibitor (IC(50) approximately 0.4 nM), has excellent passive membrane permeability, low susceptibility to P-glycoprotein transport, and lowered brain A beta levels in a mouse model. Intravenous infusion of TC-1 led to a significant but transient lowering of CSF and plasma A beta levels in conscious rhesus monkeys because it underwent CYP3A4-mediated metabolism. Oral codosing of TC-1 with ritonavir, a potent CYP3A4 inhibitor, twice daily over 3.5 days in rhesus monkeys led to sustained plasma TC-1 exposure and a significant and sustained reduction in CSF sAPP beta, A beta 40, A beta 42, and plasma A beta 40 levels. CSF A beta 42 lowering showed an EC(50) of approximately 20 nM with respect to the CSF [TC-1] levels, demonstrating excellent concordance with its potency in a cell-based assay. These results demonstrate the first in vivo proof of concept of CSF A beta lowering after oral administration of a BACE1 inhibitor in a nonhuman primate.
  Journal of Pharmacology and Experimental Therapeutics 11/2008; 328(1):131-40. · 3.83 Impact Factor
• Article: In vivo beta-secretase 1 inhibition leads to brain Abeta lowering and increased alpha-secretase processing of amyloid precursor protein without effect on neuregulin-1.

  Sethu Sankaranarayanan, Eric A Price, Guoxin Wu, Ming-Chih Crouthamel, Xiao-Ping Shi, Katherine Tugusheva, Keala X Tyler, Jason Kahana, Joan Ellis, Lixia Jin, Thomas Steele, Shawn Stachel, Craig Coburn, Adam J Simon
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  ABSTRACT: beta-Secretase (BACE) cleavage of amyloid precursor protein (APP) is one of the first steps in the production of amyloid beta peptide Abeta42, the putative neurotoxic species in Alzheimer's disease. Recent studies have shown that BACE1 knockdown leads to hypomyelination, putatively caused by a decline in neuregulin (NRG)-1 processing. In this study, we have tested a potent cell-permeable BACE1 inhibitor (IC(50) approximately 30 nM) by administering it directly into the lateral ventricles of mice, expressing human wild-type (WT)-APP, to determine the consequences of BACE1 inhibition on brain APP and NRG-1 processing. BACE1 inhibition, in vivo, led to a significant dose- and time-dependent lowering of brain Abeta40 and Abeta42. BACE1 inhibition also led to a robust brain secreted (s)APPbeta lowering that was accompanied by an increase in brain sAPPalpha levels. Although an increase in full-length NRG-1 levels was evident in 15-day-old BACE1 homozygous knockout (KO) (-/-) mice, in agreement with previous studies, this effect was also observed in 15-day-old heterozygous (+/-) mice, but it was not evident in 30-day-old and 2-year-old BACE1 KO (-/-) mice. Thus, BACE1 knockdown led to a transient decrease in NRG-1 processing in mice. Pharmacological inhibition of BACE1 in adult mice, which led to significant Abeta lowering, was without any significant effect on brain NRG-1 processing. Taken together, these results suggest that BACE1 is the major beta-site cleavage enzyme for APP and that its inhibition can lower brain Abeta and redirect APP processing via the potentially nonamyloidogenic alpha-secretase pathway, without significantly altering NRG-1 processing.
  Journal of Pharmacology and Experimental Therapeutics 04/2008; 324(3):957-69. · 3.83 Impact Factor
• Article: Design, synthesis, and SAR of macrocyclic tertiary carbinamine BACE-1 inhibitors.

  Stacey R Lindsley, Keith P Moore, Hemaka A Rajapakse, Harold G Selnick, Mary Beth Young, Hong Zhu, Sanjeev Munshi, Lawrence Kuo, Georgia B McGaughey, Dennis Colussi, [......], Eric A Price, Sethu Sankaranarayanan, Adam J Simon, Guy R Seabrook, Daria J Hazuda, Nicole T Pudvah, Jerome H Hochman, Samuel L Graham, Joseph P Vacca, Philippe G Nantermet
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  ABSTRACT: This Letter describes the design and synthesis of tertiary carbinamine macrocyclic inhibitors of the beta-secretase (BACE-1) enzyme. These macrocyclic inhibitors, some of which incorporate novel P2 substituents, display a 2- to 100-fold increase in potency relative to the previously described acyclic analogs while affording greater stability.
  Bioorganic & Medicinal Chemistry Letters 08/2007; 17(14):4057-61. · 2.55 Impact Factor
• Article: Discovery of isonicotinamide derived beta-secretase inhibitors: in vivo reduction of beta-amyloid.

  Matthew G Stanton, Shaun R Stauffer, Alison R Gregro, Melissa Steinbeiser, Philippe Nantermet, Sethu Sankaranarayanan, Eric A Price, Guoxin Wu, Ming-Chih Crouthamel, Joan Ellis, [......], Xiao-Ping Shi, Lixia Jin, Dennis Colussi, Beth Pietrak, Qian Huang, Min Xu, Adam J Simon, Samuel L Graham, Joseph P Vacca, Harold Selnick
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  ABSTRACT: beta-Secretase inhibition offers an exciting opportunity for therapeutic intervention in the progression of Alzheimer's disease. A series of isonicotinamides derived from traditional aspartyl protease transition state isostere inhibitors has been optimized to yield low nanomolar inhibitors with sufficient penetration across the blood-brain barrier to demonstrate beta-amyloid lowering in a murine model.
  Journal of Medicinal Chemistry 08/2007; 50(15):3431-3. · 5.25 Impact Factor
• Article: Evaluating scoring functions for docking and designing beta-secretase inhibitors.

  M Katharine Holloway, Georgia B McGaughey, Craig A Coburn, Shawn J Stachel, Kristen G Jones, Elizabeth L Stanton, Alison R Gregro, Ming-Tain Lai, Ming-Chih Crouthamel, Beth L Pietrak, Sanjeev K Munshi
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  ABSTRACT: Several simple scoring methods were examined for 2 series of beta-secretase (BACE-1) inhibitors to identify a docking/scoring protocol which could be used to design BACE-1 inhibitors in a drug discovery program. Both the PLP1 score and MMFFs interaction energy (E(inter)) performed as well or better than more computationally intensive methods for a set of substrate-based inhibitors, while the latter performed well for both sets of inhibitors.
  Bioorganic & Medicinal Chemistry Letters 03/2007; 17(3):823-7. · 2.55 Impact Factor
• Article: Discovery of oxadiazoyl tertiary carbinamine inhibitors of beta-secretase (BACE-1).

  Hemaka A Rajapakse, Philippe G Nantermet, Harold G Selnick, Sanjeev Munshi, Georgia B McGaughey, Stacey R Lindsley, Mary Beth Young, Ming-Tain Lai, Amy S Espeseth, Xiao-Ping Shi, [......], Beth Pietrak, Ming-Chih Crouthamel, Katherine Tugusheva, Qian Huang, Min Xu, Adam J Simon, Lawrence Kuo, Daria J Hazuda, Samuel Graham, Joseph P Vacca
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  ABSTRACT: We describe the discovery and optimization of tertiary carbinamine derived inhibitors of the enzyme beta-secretase (BACE-1). These novel non-transition-state-derived ligands incorporate a single primary amine to interact with the catalytic aspartates of the target enzyme. Optimization of this series provided inhibitors with intrinsic and functional potency comparable to evolved transition state isostere derived inhibitors of BACE-1.
  Journal of Medicinal Chemistry 01/2007; 49(25):7270-3. · 5.25 Impact Factor
• Article: A presenilin-independent aspartyl protease prefers the gamma-42 site cleavage.

  Ming-Tain Lai, Ming-Chih Crouthamel, Jillian DiMuzio, Beth Lynn Pietrak, Dorit B Donoviel, Alan Bernstein, Stephen J Gardell, Yue-Ming Li, Daria Hazuda
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  ABSTRACT: beta-Amyloid peptides (Abeta40 and Abeta42) are the major constituents of amyloid plaques, which are one of the hallmarks of Alzheimer's disease (AD). The Abeta is derived from sequential cleavages of amyloid precursor protein (APP) by beta- and gamma-secretases. gamma-Secretase consists of at least four proteins where presenilins (PS1 and PS2 or PS) are the catalytic subunit involved in the gamma-site cleavage of APP. Secretion of both Abeta40 and Abeta42 is significantly reduced in PS1 knock-out cells and completely abolished in cells deficient for both PS1 and PS2. Consequently, both the PS proteins play essential roles in the production of the secretory of Abeta from cells. Recent studies in primary neurons, however, suggest that PSs are not required for intracellular Abeta42 accumulation; thus the intracellular Abeta42 appears to be generated in a PS-independent manner. Here we present the first biochemical evidence indicating that Abeta, especially Abeta42, can be generated in the absence of PS based on an in vitrogamma-secretase assay employing membranes prepared from PS-deficient Blastocyst-derived (BD) cells. This PS-independent gamma-secretase (PSIG) activity is sensitive to the changes in pH and displays an optimal activity at pH 6.0. Pepstatin A is a potent inhibitor for this proteolytic activity with IC50 of 1.2 nm and 0.4 nm for Abeta40 and Abeta42 generation, respectively. These results indicate that these PS-independent gamma-site cleavages are mediated by an aspartyl protease. More importantly, the PSIG activity displays a distinct preference in mediating the 42-site cleavage over the 40-site cleavage, thereby generating Abeta42 as the predominant product.
  Journal of Neurochemistry 02/2006; 96(1):118-25. · 4.06 Impact Factor
• Article: Biochemical and cell-based assays for characterization of BACE-1 inhibitors.

  Beth L Pietrak, Ming-Chih Crouthamel, Katherine Tugusheva, Janet E Lineberger, Min Xu, Jillian M DiMuzio, Thomas Steele, Amy S Espeseth, Shawn J Stachel, Craig A Coburn, Samuel L Graham, Joseph P Vacca, Xiao-Ping Shi, Adam J Simon, Daria J Hazuda, Ming-Tain Lai
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  ABSTRACT: The deposition of beta-amyloid peptides (A beta42 and A beta40) in neuritic plaques is one of the hallmarks of Alzheimer's disease (AD). A beta peptides are derived from sequential cleavage of amyloid precursor protein (APP) by beta- and gamma-secretases. BACE-1 has been shown to be the major beta-secretase and is a primary therapeutic target for AD. In this article, two novel assays for the characterization of BACE-1 inhibitors are reported. The first is a sensitive 96-well HPLC biochemical assay that uses a unique substrate containing an optimized peptide cleavage sequence, NFEV, spanning from the P2-P2' positions This substrate was processed by BACE-1 approximately 10 times more efficiently than was the widely used substrate containing the Swedish (NLDA) sequence. As a result, the concentration of the enzyme required for the assay can be as low as 100 pM, permitting the evaluation of inhibitors with subnanomolar potency. The assay has also been applied to related aspartyl proteases such as cathepsin D (Cat D) and BACE-2. The second assay is a homogeneous electrochemiluminescence assay for the evaluation of BACE-1 inhibition in cultured cells that assesses the level of secreted amyloid EV40_NF from HEK293T cells stably transfected with APP containing the novel NFEV sequence. To illustrate the use of these assays, the properties of a potent, cell-active BACE-1 inhibitor are described.
  Analytical Biochemistry 08/2005; 342(1):144-51. · 3.00 Impact Factor
• Article: Compounds that bind APP and inhibit Abeta processing in vitro suggest a novel approach to Alzheimer disease therapeutics.

  Amy S Espeseth, Min Xu, Qian Huang, Craig A Coburn, Kristen L G Jones, Marc Ferrer, Paul D Zuck, Berta Strulovici, Eric A Price, Guoxin Wu, [......], Katherine Tugusheva, Beth L Pietrak, Ming-Chih Crouthamel, Ming-Tain Lai, Elizabeth Chen Dodson, Renzo Bazzo, Xiao-Ping Shi, Adam J Simon, Yueming Li, Daria J Hazuda
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  ABSTRACT: Extracellular deposits of aggregated amyloid-beta (Abeta) peptides are a hallmark of Alzheimer disease; thus, inhibition of Abeta production and/or aggregation is an appealing strategy to thwart the onset and progression of this disease. The release of Abeta requires processing of the amyloid precursor protein (APP) by both beta- and gamma-secretase. Using an assay that incorporates full-length recombinant APP as a substrate for beta-secretase (BACE), we have identified a series of compounds that inhibit APP processing, but do not affect the cleavage of peptide substrates by BACE1. These molecules also inhibit the processing of APP and Abeta by BACE2 and selectively inhibit the production of Abeta(42) species by gamma-secretase in assays using CTF99. The compounds bind directly to APP, likely within the Abeta domain, and therefore, unlike previously described inhibitors of the secretase enzymes, their mechanism of action is mediated through APP. These studies demonstrate that APP binding agents can affect its processing through multiple pathways, providing proof of concept for novel strategies aimed at selectively modulating Abeta production.
  Journal of Biological Chemistry 06/2005; 280(18):17792-7. · 4.77 Impact Factor
• Article: Compounds That Bind APP and Inhibit Aβ Processing in Vitro Suggest a Novel Approach to Alzheimer Disease Therapeutics

  Amy S. Espeseth, Min Xu, Qian Huang, Craig A. Coburn, Kristen L. G. Jones, Marc Ferrer, Paul D. Zuck, Berta Strulovici, Eric A. Price, Guoxin Wu, [......], Katherine Tugusheva, Beth L. Pietrak, Ming-Chih Crouthamel, Ming-Tain Lai, Elizabeth Chen Dodson, Renzo Bazzo, Xiao-Ping Shi, Adam J. Simon, Yueming Li, Daria J. Hazuda
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  ABSTRACT: Extracellular deposits of aggregated amyloid-β (Aβ) peptides are a hallmark of Alzheimer disease; thus, inhibition of Aβ production and/or aggregation is an appealing strategy to thwart the onset and progression of this disease. The release of Aβ requires processing of the amyloid precursor protein (APP) by both β- and γ-secretase. Using an assay that incorporates full-length recombinant APP as a substrate for β-secretase (BACE), we have identified a series of compounds that inhibit APP processing, but do not affect the cleavage of peptide substrates by BACE1. These molecules also inhibit the processing of APP and Aβ by BACE2 and selectively inhibit the production of Aβ42 species by γ-secretase in assays using CTF99. The compounds bind directly to APP, likely within the Aβ domain, and therefore, unlike previously described inhibitors of the secretase enzymes, their mechanism of action is mediated through APP. These studies demonstrate that APP binding agents can affect its processing through multiple pathways, providing proof of concept for novel strategies aimed at selectively modulating Aβ production.
  Journal of Biological Chemistry 05/2005; 280(18):17792-17797. · 4.77 Impact Factor
• Article: Novel mutations introduced at the beta-site of amyloid beta protein precursor enhance the production of amyloid beta peptide by BACE1 in vitro and in cells.

  Xiao-Ping Shi, Katherine Tugusheva, James E Bruce, Adam Lucka, Elizabeth Chen-Dodson, Binghua Hu, Guo-Xin Wu, Eric Price, Robert B Register, Janet Lineberger, [......], Lin Chen, Ming-Tain Lai, Beth Pietrak, Jillian DiMuzio, Yueming Li, Min Xu, Qian Huang, Victor Garsky, Mohinder K Sardana, Daria J Hazuda
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  ABSTRACT: Abnormal production and accumulation of amyloid-beta peptide (Abeta) plays a major role in the pathogenesis of Alzheimer's disease (AD). beta-secretase (BACE1) is responsible for the cleavage at thebeta-site in amyloid beta protein precursor (AbetaPP/APP) to generate the N-terminus of Abeta. Here we report the stepwise identification and characterization of a novel APP-beta-site mutant, "NFEV" (APP_NFEV) in vitro and in cells. In vitro, the APP_NFEV exhibits 100-fold enhanced cleavage rate relative to the "wild-type" substrate (APPwt) and 10-fold increase relative to the Swedish-type mutation variant (APPsw). In cells, it was preferably cleaved among 24 APP beta-site mutations tested. More importantly, the APP_NFEV mutant failed to generate any detectable Abeta peptides in BACE1-KO mouse fibroblast cells. The production of Abeta peptides was restored by co-transfecting human BACE1, demonstrating that BACE1 is the only enzyme responsible for the processing of APP_NFEV in these cells. Analysis of APP_NFEV cleavage products secreted in the media revealed that in cells BACE1 cleaves APP_NFEV at the position between NF and EV, identical to that observed in vitro. A BACE inhibitor blocked the processing of the APP_NFEV beta-site in vitro and in cells. Our data indicates that the "NFEV" mutant is not only an enhanced substrate for BACE1 in vitro, but also a specific substrate for BACE1 in cells.
  Journal of Alzheimer's disease: JAD 05/2005; 7(2):139-48; discussion 173-80. · 3.74 Impact Factor
• Article: Identification of a small molecule nonpeptide active site beta-secretase inhibitor that displays a nontraditional binding mode for aspartyl proteases.

  Craig A Coburn, Shawn J Stachel, Yue-Ming Li, Diane M Rush, Thomas G Steele, Elizabeth Chen-Dodson, M Katharine Holloway, Min Xu, Qian Huang, Ming-Tain Lai, [......], Vinod Sardana, Zhongguo Chen, Sanjeev Munshi, Lawrence Kuo, Gergely M Makara, D Allen Annis, Praveen K Tadikonda, Huw M Nash, Joseph P Vacca, Tong Wang
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  ABSTRACT: A small molecule nonpeptide inhibitor of beta-secretase has been developed, and its binding has been defined through crystallographic determination of the enzyme-inhibitor complex. The molecule is shown to bind to the catalytic aspartate residues in an unprecedented manner in the field of aspartyl protease inhibition. Additionally, the complex reveals a heretofore unknown S(3) subpocket that is created by the inhibitor. This structure has served an important role in the design of newer beta-secretase inhibitors.
  Journal of Medicinal Chemistry 01/2005; 47(25):6117-9. · 5.25 Impact Factor
• Article: Structure-based design of potent and selective cell-permeable inhibitors of human beta-secretase (BACE-1).

  Shawn J Stachel, Craig A Coburn, Thomas G Steele, Kristen G Jones, Elizabeth F Loutzenhiser, Alison R Gregro, Hemaka A Rajapakse, Ming-Tain Lai, Ming-Chih Crouthamel, Min Xu, [......], Janet E Lineberger, Beth L Pietrak, Amy S Espeseth, Xiao-Ping Shi, Elizabeth Chen-Dodson, M Katharine Holloway, Sanjeev Munshi, Adam J Simon, Lawrence Kuo, Joseph P Vacca
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  ABSTRACT: We describe the development of cell-permeable beta-secretase inhibitors that demonstratively inhibit the production of the secreted amino terminal fragment of an artificial amyloid precursor protein in cell culture. In addition to potent inhibition in a cell-based assay (IC50 < 100 nM), these inhibitors display impressive selectivity against other biologically relevant aspartyl proteases.
  Journal of Medicinal Chemistry 01/2005; 47(26):6447-50. · 5.25 Impact Factor
• Article: Structure-Based Design of Potent and Selective Cell-Permeable Inhibitors of Human β-Secretase (BACE-1)

  Shawn J. Stachel, Craig A. Coburn, Thomas G. Steele, Kristen G. Jones, Elizabeth F. Loutzenhiser, Alison R. Gregro, Hemaka A. Rajapakse, Ming-Tain Lai, Ming-Chih Crouthamel, Min Xu, [......], Janet E. Lineberger, Beth L. Pietrak, Amy S. Espeseth, Xiao-Ping Shi, Elizabeth Chen-Dodson, M. Katharine Holloway, Sanjeev Munshi, Adam J. Simon, Lawrence Kuo, Joseph P. Vacca
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  ABSTRACT: We describe the development of cell-permeable β-secretase inhibitors that demonstratively inhibit the production of the secreted amino terminal fragment of an artificial amyloid precursor protein in cell culture. In addition to potent inhibition in a cell-based assay (IC50 < 100 nM), these inhibitors display impressive selectivity against other biologically relevant aspartyl proteases.
  11/2004;
• Source

  Available from: Michael W Pennington

  Article: Rational design and synthesis of selective BACE-1 inhibitors.

  Stephen F Brady, Satendra Singh, Ming Chih Crouthamel, M Katharine Holloway, Craig A Coburn, Victor M Garsky, Michael Bogusky, Michael W Pennington, Joseph P Vacca, Daria Hazuda, Ming-Tain Lai
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  ABSTRACT: An effective approach for enhancing the selectivity of beta-site amyloid precursor protein cleaving enzyme (BACE 1) inhibitors is developed based on the unique features of the S1' pocket of the enzyme. A series of low molecular weight (<600) compounds were synthesized with different moieties at the P1' position. The selectivity of BACE 1 inhibitors versus cathepsin D and renin was enhanced 120-fold by replacing the hydrophobic propyl group with a hydrophilic propionic acid group.
  Bioorganic & Medicinal Chemistry Letters 03/2004; 14(3):601-4. · 2.55 Impact Factor
• Article: Presenilin-1 and presenilin-2 exhibit distinct yet overlapping gamma-secretase activities.

  Ming-Tain Lai, Elizabeth Chen, Ming-Chih Crouthamel, Jillian DiMuzio-Mower, Min Xu, Qian Huang, Eric Price, R Bruce Register, Xiao-Ping Shi, Dorit B Donoviel, Alan Bernstein, Daria Hazuda, Stephen J Gardell, Yue-Ming Li
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  ABSTRACT: Presenilin-1 (PS1) and presenilin 2 (PS2) are proposed to be transmembrane aspartyl proteases that cleave amyloid precursor protein and Notch. PS1- and PS2-mediated activities were individually characterized using blastocyst-derived (BD) cells and membranes from PS1+/--PS2-/- and PS1-/-PS2+/+ mice, respectively. The relative amounts of PS1 and PS2 in the various BD cells were determined from the intensities of the anti-PS1 and anti-PS2 immunoblot signals by comparison with standard curves using radiolabeled PS1 and PS2 standards produced by in vitro transcription and translation. Cellular membranes from wild type, PS1-/-PS2+/+, and PS1+/--PS2-/- but not PS1-/-PS2-/- BD cells generated the Abeta40 and Abeta42 products from the C100FLAG substrate. PS1-associated gamma-secretase displays considerably higher specific activity than PS2-associated gamma-secretase. Moreover, the PS1+/-PS2-/- BD cells and corresponding membranes exhibited much higher gamma-secretase activity as compared with other BD cells and membranes. The PS1-mediated gamma-secretase activity correlated better with the amount of PS1 that is modifiable by a photoactivated active site-directed gamma-secretase inhibitor rather than total PS1; hence, only a small portion (<14%) of the PS1 in wild-type membranes appears to be engaged in an active gamma-secretase complex. This finding suggests that PS1 may serve other biological functions in addition to that associated with its gamma-secretase activity. Furthermore, the PS1 gamma-secretase complex and the PS2 gamma-secretase complex activities can be discriminated on the basis of their susceptibility to inhibition by a potent gamma-secretase inhibitor. The distinct yet overlapping enzymatic properties of the PS1 gamma-secretase complex and the PS2 gamma-secretase complex imply that these two putative aspartyl class proteases may contribute to different biological processes.
  Journal of Biological Chemistry 07/2003; 278(25):22475-81. · 4.77 Impact Factor