Alzheimer's disease is a devastating neurodegenerative disorder characterized by the cerebral deposition of ?-amyloid peptides (A?), generated by sequential proteolysis of amyloid precursor protein (APP) by BACE1 and ?-secretase. There has been considerable epidemiological interest in the relationship between cholesterol and susceptibility to Alzheimer's disease. Evidence from a variety of in vitro and in vivo studies indicates that cholesterol- and sphingolipid-rich membrane microdomains, termed lipid rafts, might be a critical link between cellular cholesterol levels and amyloidogenic processing of APP. Indeed, each of the ?-secretase subunits and APP C-terminal fragments (CTF) are enriched in lipid rafts isolated from brain;full-length APP and BACE1 are also found in lipid rafts, albeit at lower levels. Notably, BACE1 and two ?-secretase subunits (nicastrin and APH1) undergo S-palmitoylation, a post-translational lipid modification commonly found in raft-associated proteins. In addition to lipid raft targeting, S-palmitoylation is a critical modification that dynamically regulates membrane trafficking and modulates the function of proteins such as neuronal transmembrane (AMPA and NMDA receptors) and cytosolic proteins (PSD-95). The in vivo physiological significance of S-palmitoylation of APP secretases in neurons remains unknown. We have begun to address this important issue using transgenic mice and by applying novel live-cell imaging strategies in hippocampal neurons. In unpublished preliminary studies we observe a significant decrease in amyloid burden in the brains of transgenic mice expressing S-palmitoylation-deficient ?-secretase subunits. Moreover, in hippocampal neurons we have discovered S-palmitoylation-dependent differential regulation of BACE1 trafficking to the neuronal cell surface, localization in dendritic spines, and axonal transport. These later findings are highly relevant to Alzheimer's disease pathogenesis because in neurons APP is trafficked anterogradely along peripheral and central axons, and proteolytically processed during transit. Therefore, it is extremely important to perform functional analysis of S-palmitoylation-deficient BACE1 in neurons at physiological expression levels in vivo to unequivocally determine how S-palmitoylation of BACE1 regulates APP processing and amyloid deposition in the brain. The following are the specific aims of this investigation.
Aim 1 : To perform functional analysis of ?-secretase S-palmitoylation in transgenic mice.
Aim 2 : To perform functional characterization of BACE1 S-palmitoylation in vivo.
Aim 3 : To investigate the dynamic regulation of BACE1 trafficking by S-palmitoylation. Our studies will uncover novel and significant insights on differential regulation of AP secretase localization and function by S-palmitoylation in cultured hippocampal neurons and in vivo.

Public Health Relevance

Alzheimer's disease (AD) is the major cause of dementia in the elderly, afflicting more than 50% of the population over 80 years of age;presently 5.1 million Americans suffer from this devastating disorder. AD patients as well as aged individuals accumulate beta-amyloid peptides as deposits in brain, called senile plaques. Using cultured cells, transgenic mice, and knock-in mice as experimental models we investigate how post-translational modification of APP secretases and their dynamic movement in cells regulate beta-amyloid production and deposition. Our studies will be critical to develop novel rational AD therapeutics aimed at reducing beta-amyloid burden in the brain.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Research Project (R01)
Project #
3R01AG019070-13S1
Application #
8716872
Study Section
Cell Death in Neurodegeneration Study Section (CDIN)
Program Officer
Petanceska, Suzana
Project Start
2001-03-15
Project End
2015-06-30
Budget Start
2013-08-15
Budget End
2014-06-30
Support Year
13
Fiscal Year
2013
Total Cost
$65,058
Indirect Cost
$20,358
Name
University of Chicago
Department
Biology
Type
Schools of Medicine
DUNS #
005421136
City
Chicago
State
IL
Country
United States
Zip Code
60637
Sadleir, Katherine R; Kandalepas, Patty C; Buggia-Prévot, Virginie et al. (2016) Presynaptic dystrophic neurites surrounding amyloid plaques are sites of microtubule disruption, BACE1 elevation, and increased Aβ generation in Alzheimer's disease. Acta Neuropathol 132:235-56
De Rossi, Pierre; Buggia-Prévot, Virginie; Clayton, Benjamin L L et al. (2016) Predominant expression of Alzheimer's disease-associated BIN1 in mature oligodendrocytes and localization to white matter tracts. Mol Neurodegener 11:59
Andrew, Robert J; Kellett, Katherine A B; Thinakaran, Gopal et al. (2016) A Greek Tragedy: The Growing Complexity of Alzheimer Amyloid Precursor Protein Proteolysis. J Biol Chem 291:19235-44
Deyts, Carole; Thinakaran, Gopal; Parent, Angèle T (2016) APP Receptor? To Be or Not To Be. Trends Pharmacol Sci 37:390-411
Wang, Y; Buggia-Prévot, V; Zavorka, M E et al. (2015) Overexpression of the Insulin-Like Growth Factor II Receptor Increases β-Amyloid Production and Affects Cell Viability. Mol Cell Biol 35:2368-84
Buggia-Prévot, Virginie; Thinakaran, Gopal (2015) Significance of transcytosis in Alzheimer's disease: BACE1 takes the scenic route to axons. Bioessays 37:888-98
Tkatchenko, Andrei V; Tkatchenko, Tatiana V; Guggenheim, Jeremy A et al. (2015) APLP2 Regulates Refractive Error and Myopia Development in Mice and Humans. PLoS Genet 11:e1005432
Wang, Yanlin; Thinakaran, Gopal; Kar, Satyabrata (2014) Overexpression of the IGF-II/M6P receptor in mouse fibroblast cell lines differentially alters expression profiles of genes involved in Alzheimer's disease-related pathology. PLoS One 9:e98057
Buggia-Prévot, Virginie; Thinakaran, Gopal (2014) Sorting the role of SORLA in Alzheimer's disease. Sci Transl Med 6:223fs8
Buggia-Prévot, Virginie; Fernandez, Celia G; Riordan, Sean et al. (2014) Axonal BACE1 dynamics and targeting in hippocampal neurons: a role for Rab11 GTPase. Mol Neurodegener 9:1

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