Gamma-secretase catalyzed cleavages are of interest for a number of reasons. First, gamma-secretase is an unusual proteolytic activity with the cleavage site of the substrate predicted to lie within the transmembrane domain. Moreover, position of the gamma-cleavage site with respect to the membrane, not the primary amino acid sequence, appears to be the major determinant of cleavage, with the length of the lumenal transmembrane domain (TMD) determining that position. Whether gamma-secretase actually cleaves residues within the membrane is a subject of much controversy. To date, there is no evidence showing that a protease can cleave bonds buried within a membrane. Second, altered gamma-secretase cleavage is implicated in the development of AD. With the exception of the APPK670N,M67IL mutation, all FAD-linked mutations alter gamma-secretase activity by increasing the amount of the more amyloidogenic Abeta species, Abeta 42. Third, APP carboxyl terminal fragments (CTF) do not appear to be the only substrate for gamma-secretase activity. The cell surface receptor Notch undergoes processing analogous to APP. Several sequential cleavages in the lumenal/extracellular domain are followed by a final cleavage of residues near the cytoplasm/membrane junction mediated by a gamma-secretase like cleavage. Finally, because gamma-secretase cleavage is the final step in the generation of Abeta, it remains a major therapeutic target for strategies designed to lower Abeta production. Thus, gamma-secretase is not only an unusual proteolytic event, but its activity has important biological consequences both in the normal state and with respect to pathogenesis and treatment of AD. To further characterize and ultimately identify the proteases responsible for the gamma-secretase activity we propose to: 1. Map the position of the gamma-secretase site with respect to the membrane in full length APP versus an APP CTF using biochemical methods and then determine whether mutations that alter gamma-secretase cleavage alter membrane positioning of APP CTF. 2. Determine the relative potency of gamma-secretase inhibitors using an in vitro gamma-secretase activity assay. 3. Purify gamma-secretase using affinity based approaches to identify candidate candidate gamma-secretases that will then be screened for gamma-activity by sense and antisense expression studies.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS039072-03
Application #
6540148
Study Section
Special Emphasis Panel (ZRG1-MDCN-2 (01))
Program Officer
Murphy, Diane
Project Start
2000-04-10
Project End
2003-03-31
Budget Start
2002-04-01
Budget End
2003-03-31
Support Year
3
Fiscal Year
2002
Total Cost
$306,000
Indirect Cost
Name
Mayo Clinic, Jacksonville
Department
Type
DUNS #
153223151
City
Jacksonville
State
FL
Country
United States
Zip Code
32224
Golde, Todd E; Petrucelli, Leonard; Lewis, Jada (2010) Targeting Abeta and tau in Alzheimer's disease, an early interim report. Exp Neurol 223:252-66
Golde, Todd E; Wolfe, Michael S; Greenbaum, Doron C (2009) Signal peptide peptidases: a family of intramembrane-cleaving proteases that cleave type 2 transmembrane proteins. Semin Cell Dev Biol 20:225-30
Nyborg, Andrew C; Ladd, Thomas B; Jansen, Karen et al. (2006) Intramembrane proteolytic cleavage by human signal peptide peptidase like 3 and malaria signal peptide peptidase. FASEB J 20:1671-9
Wang, Jun; Beher, Dirk; Nyborg, Andrew C et al. (2006) C-terminal PAL motif of presenilin and presenilin homologues required for normal active site conformation. J Neurochem 96:218-27
Nyborg, Andrew C; Jansen, Karen; Ladd, Thomas B et al. (2004) A signal peptide peptidase (SPP) reporter activity assay based on the cleavage of type II membrane protein substrates provides further evidence for an inverted orientation of the SPP active site relative to presenilin. J Biol Chem 279:43148-56
Nyborg, Andrew C; Kornilova, Anna Y; Jansen, Karen et al. (2004) Signal peptide peptidase forms a homodimer that is labeled by an active site-directed gamma-secretase inhibitor. J Biol Chem 279:15153-60
Martoglio, Bruno; Golde, Todd E (2003) Intramembrane-cleaving aspartic proteases and disease: presenilins, signal peptide peptidase and their homologs. Hum Mol Genet 12 Spec No 2:R201-6
Piper, Sian C; Amtul, Zareen; Galinanes-Garcia, Laura et al. (2003) Peptide-based, irreversible inhibitors of gamma-secretase activity. Biochem Biophys Res Commun 305:529-33
Ramsden, M; Nyborg, A C; Murphy, M P et al. (2003) Androgens modulate beta-amyloid levels in male rat brain. J Neurochem 87:1052-5
Leissring, Malcolm A; Murphy, M Paul; Mead, Tonya R et al. (2002) A physiologic signaling role for the gamma -secretase-derived intracellular fragment of APP. Proc Natl Acad Sci U S A 99:4697-702

Showing the most recent 10 out of 15 publications