Promotion of tau phosphorylation by MAP kinase Erk1/2 is accompanied by reduced cholesterol level in detergent-insoluble membrane fraction in Niemann-Pick C1-deficient cells.
Niemann-Pick type C (NPC) disease is a cholesterol-storage disease accompanied by neurodegeneration with the formation of neurofibrillary tangles, the major component of which is the hyperphosphorylated tau. Here, we examined the mechanism underlying hyperphosphorylation of tau using mutant Chinese hamster ovary (CHO) cell line defective in NPC1 (CT43) as a tool. Immunoblot analysis revealed that tau was hyperphosphorylated at multiple sites in CT43 cells, but not in their parental cells (25RA) or the wild-type CHO cells. In CT43 cells, mitogen-activated protein (MAP) kinase Erk1/2 was activated and the specific MAPK inhibitor, PD98059, attenuated the hyperphosphorylation of tau. The amount of protein phosphatase 2A not bound to microtubules was decreased in CT43 cells. CT43 cells but not 25RA cells were amphotericin B-resistant, indicating that cholesterol level in the plasma membrane of CT43 is decreased. In addition, the level of cholesterol in the detergent-insoluble, low-density membrane (LDM) fraction of CT43 cells was markedly reduced compared with the other two types of CHO cells. As LDM domain plays critical role in signaling pathways, these results suggest that the reduced cholesterol level in LDM domain due to the lack of NPC1 may activate MAPK, which subsequently promotes tau phosphorylation in NPC1-deficient cells.
Sawamura
Naoya
N
Department of Dementia Research, National Institute for Longevity Sciences, 36-3 Gengo, Morioka, Obu, Aichi 474-8522, Japan.
Gong
Jian-Sheng
JS
Chang
Ta-Yuan
TY
Yanagisawa
Katsuhiko
K
Michikawa
Makoto
M
D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D002784:Cholesterol / Q000032:analysis / Q000378:metabolism*; D006224:Cricetinae; D003902:Detergents / Q000737:chemistry; D005260:Female; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D050356:Lipid Metabolism; D008055:Lipids / Q000032:analysis; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009542:Niemann-Pick Diseases / Q000378:metabolism*; D010053:Ovary / Q000166:cytology / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D054648:Protein Phosphatase 2; D012995:Solubility; D013347:Subcellular Fractions / Q000737:chemistry; D014162:Transfection; D016875:tau Proteins / Q000378:metabolism*
D003902:Detergents; D008055:Lipids; D016875:tau Proteins; D002784:Cholesterol; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2