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Figure 1. The effects of overexpression of PTEN proteins on tau phosphorylation and aggregation. A) Schematic drawing of human tau and major phosphorylation sites by various kinases. The sites examined are in bold. Kinases are abbreviated as following, M, MAPK; G, GSK-3; C5, CDK5; A, PKA; C, PKC; PK, phosphorylase kinase. B) pcDNA, wild-type (PTEN-WT) or lipid phosphatase null mutant PTEN (PTEN-CG) transfected COS-7 cells were analyzed by Western blots using phospho-tau specific antibodies as indicated. C) Levels of phospho-tau were quantified and normalized to total tau levels. Error bars indicate means ± SE, n=4, *P > 0.01 and **P > 0.02 compared with the respective controls (vector alone). D) COS-7 cells transiently overexpressing wild-type tau (T40) were further transfected with pcDNA vector, PTEN-WT, or PTEN-CG. Insoluble aggregated tau proteins were isolated and detected by using a filter-trap/immunoblotting assay (upper panels). Transfected PTEN and total tau proteins (as indicated in middle and lower panels) were detected by Western blots from same amounts of lysates as in filter assays. E) The amounts of aggregated tau protein were quantified by densitometry and normalized using the amounts of total tau. Error bars indicate means ± SE, n = 3, *P > 0.01 compared with the vector transfection control.
