Nuclear 82-kDa choline acetyltransferase decreases amyloidogenic APP metabolism in neurons from APP/PS1 transgenic mice.
Alzheimer disease (AD) is associated with increased amyloidogenic processing of amyloid precursor protein (APP) to β-amyloid peptides (Aβ), cholinergic neuron loss with decreased choline acetyltransferase (ChAT) activity, and cognitive dysfunction. Both 69-kDa ChAT and 82-kDa ChAT are expressed in cholinergic neurons in human brain and spinal cord with 82-kDa ChAT localized predominantly to neuronal nuclei, suggesting potential alternative functional roles for the enzyme. By gene microarray analysis, we found that 82-kDa ChAT-expressing IMR32 neural cells have altered expression of genes involved in diverse cellular functions. Importantly, genes for several proteins that regulate APP processing along amyloidogenic and non-amyloidogenic pathways are differentially expressed in 82-kDa ChAT-containing cells. The predicted net effect based on observed changes in expression patterns of these genes would be decreased amyloidogenic APP processing with decreased Aβ production. This functional outcome was verified experimentally as a significant decrease in BACE1 protein levels and activity and a concomitant reduction in the release of endogenous Aβ1-42 from neurons cultured from brains of AD-model APP/PS1 transgenic mice. The expression of 82-kDa ChAT in neurons increased levels of GGA3, which is involved in trafficking BACE1 to lysosomes for degradation. shRNA-induced decreases in GGA3 protein levels attenuated the 82-kDa ChAT-mediated decreases in BACE1 protein and activity and Aβ1-42 release. Evidence that 82-kDa ChAT can enhance GGA3 gene expression is shown by enhanced GGA3 gene promoter activity in SN56 neural cells expressing this ChAT protein. These studies indicate a novel relationship between cholinergic neurons and APP processing, with 82-kDa ChAT acting as a negative regulator of Aβ production. This decreased formation of Aβ could result in protection for cholinergic neurons, as well as protection of other cells in the vicinity that are sensitive to increased levels of Aβ. Decreasing levels of 82-kDa ChAT due to increasing age or neurodegeneration could alter the balance towards increasing Aβ production, with this potentiating the decline in function of cholinergic neurons.
Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, Molecular Medicine Research Group, Robarts Research Institute, London, Ontario, Canada.
Shawn
S
Albers
Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, Molecular Medicine Research Group, Robarts Research Institute, London, Ontario, Canada.
Fatima
F
Inthathirath
Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, Molecular Medicine Research Group, Robarts Research Institute, London, Ontario, Canada.
Sandeep K
SK
Gill
Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, Molecular Medicine Research Group, Robarts Research Institute, London, Ontario, Canada.
Warren
W
Winick-Ng
Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, Molecular Medicine Research Group, Robarts Research Institute, London, Ontario, Canada.
Ewa
E
Jaworski
Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, Molecular Medicine Research Group, Robarts Research Institute, London, Ontario, Canada.
Daisy Y L
DY
Wong
Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, Molecular Medicine Research Group, Robarts Research Institute, London, Ontario, Canada.
Robert
R
Gros
Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, Molecular Medicine Research Group, Robarts Research Institute, London, Ontario, Canada. Electronic address: jane.rylett@schulich.uwo.ca.
R Jane
RJ
Rylett
D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics / Q000378:metabolism; D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism; D001921:Brain / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D002795:Choline O-Acetyltransferase / Q000378:metabolism*; D059329:Cholinergic Neurons / Q000378:metabolism; D015870:Gene Expression; D057809:HEK293 Cells; D006801:Humans; D008822:Mice, Transgenic; D046228:Microarray Analysis; D009474:Neurons / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D053764:Presenilin-1 / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic
C545487:APP protein, human; D033942:Adaptor Proteins, Vesicular Transport; D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; C407306:GGA adaptor proteins; C508853:PSEN1 protein, human; D010446:Peptide Fragments; D053764:Presenilin-1; C075222:amyloid beta-protein (1-42); D002795:Choline O-Acetyltransferase; D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; C509282:Bace1 protein, mouse
Alzheimer disease; Amyloid; Amyloidogenic; BACE1; Choline acetyltransferase; Cholinergic; GGA3; Microarray; Neuron cultures; Nuclear