FIG. 8.

SGK1 increases hippocampal neurite formation through the phosphorylation of tau at Ser214. (A) pEGFP-sgk1 (green), pDsRed-tauS214A (red) or the combination of pEGFP-sgk1 and pDsRed-tauS214A was transfected to dissociated hippocampal neurons at DIV 0 and fixed at DIV 1. Neuronal processes were visualized by immunostaining with anti-β III tubulin Ab (blue). The EGFP-SGK1 and DsRed-TauS214A fusion proteins were readily observed with a confocal fluorescence microscope. Scale bar, 10 μm. (B) The transfection of sgk1 markedly increased the number of primary neurites, and this effect was reversed by the cotransfection of tauS214A. (C) The transfection of sgk1 also decreased the length of the total process, and this effect was antagonized by the cotransfection of tauS214A. n = 70, 64, 44, and 69 for vector, pDsRed-tauS214A, pEGFP-sgk1 and pEGFP-sgk1+pDsRed-tauS214A groups, respectively. Data are expressed as means ± standard errors of the means (error bars). **, P was <0.01 as determined by one-way analysis of variance, followed by Dunnett's t test, compared with that of the vector transfection group; # #, P was <0.01, as determined by one-way analysis of variance, followed by Newman-Keuls statistics, compared with that of the sgk1 transfection group.