title: U18666A-mediated apoptosis in cultured murine cortical neurons: role of caspases, calpains and kinases.
abstract: Studies have suggested that cholesterol imbalance in the brain might be related to the development of neurological disorders such as Alzheimer's disease and Niemann-Pick disease type C. Previously, we have reported that U18666A, a cholesterol transport-inhibiting agent, leads to apoptosis and intracellular cholesterol accumulation in primary cortical neurons. In this study, we examined the effects of U18666A-mediated neuronal apoptosis, and found that chronic exposure to U18666A led to the activation of caspases and calpains and hyperphosphorylation of tau. Tau hyperphosphorylation is regulated by several kinases that phosphorylate specific sites of tau in vitro. Surprisingly, the kinase activity of cyclin-dependent kinase 5 decreased in U18666A-treated cortical neurons whereas its protein level remained unchanged. The amount of glycogen synthase kinase 3 and mitogen-activated protein kinases were found to decrease in their phosphorylated states by Western blot analysis. Gene transcription was further studied using microarray analysis. Genes encoding for kinases and phosphatases were differentially expressed with most up-regulated and some down-regulated in expression upon U18666A treatment. The activation of cysteine proteases and cholesterol accumulation with tauopathies may provide clues to the cellular mechanism of the inhibition of cholesterol transport-mediated cell death in neurodegenerative diseases.
authors.affiliation: Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 117597, Singapore.
authors.forename: Chor Hui Vivien
authors.initials: CH
authors.lastname: Koh
authors.forename: Robert Z
authors.initials: RZ
authors.lastname: Qi
authors.forename: Dianbo
authors.initials: D
authors.lastname: Qu
authors.forename: Alirio
authors.initials: A
authors.lastname: Melendez
authors.forename: Jayapal
authors.initials: J
authors.lastname: Manikandan
authors.forename: Boon Huat
authors.initials: BH
authors.lastname: Bay
authors.forename: Wei
authors.initials: W
authors.lastname: Duan
authors.forename: Nam Sang
authors.initials: NS
authors.lastname: Cheung
mesh_terms: D000736:Androstenes / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002154:Calpain / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured; D051360:Cyclin-Dependent Kinase 5 / Q000378:metabolism; D003599:Cytoskeleton / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D051379:Mice; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016875:tau Proteins / Q000378:metabolism
chemical_list: D000736:Androstenes; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; C089495:neuronal Cdk5 activator (p25-p35); D016875:tau Proteins; C006261:3-beta-(2-(diethylamino)ethoxy)androst-5-en-17-one; D051360:Cyclin-Dependent Kinase 5; D048031:JNK Mitogen-Activated Protein Kinases; D048052:Mitogen-Activated Protein Kinase 3; D038362:Glycogen Synthase Kinase 3; D010749:Phosphoprotein Phosphatases; D002154:Calpain; D020169:Caspases