Figure 1.

MARK4^ΔG316E317D increases the level of tau to a greater extent than MARK4^wt. A, (top) schematic representation of MARK4 and ΔG316E317D mutation. (bottom) MARK4^wt and MARK4^ΔG316E317D are expressed at similar levels in fly eyes. MARK4 expression was driven by the pan-retinal driver GMR-Gal4. Levels of MARK4^wt or MARK4^ΔG316E317D in fly head lysates were examined by Western blotting. Actin was used as a loading control. Representative blots (left panels) and quantification (right panels) are shown. B, coexpression of MARK4^wt increased the levels of phosphorylated tau and total tau, and coexpression of MARK4^ΔG316E317D increased the levels of total tau, pSer-262–tau, and pSer-356–tau in the eyes to a significantly greater extent than MARK4^wt. Western blotting was performed with anti-tau antibody T46 (tau), anti-phospho–Ser-262 tau antibody (pSer-262), or anti-phospho–Ser-356 antibody (pSer-356). Representative blots (top) and quantification normalized to actin, or to total tau (bottom panels), are shown. C, coexpression of MARK4^wt or MARK4^ΔG316E317D does not affect tau mRNA levels. mRNA levels of tau expressed alone (tau), tau coexpressed with MARK4^wt (tau+MARK4^wt), and tau coexpressed with MARK4^ΔG316E317D (tau+MARK4^ΔG316E317D) were measured by quantitative PCR. Means ± S.D. (error bars); n = 4. n.s. (not significant), p > 0.05; *p < 0.05; **p < 0.01; ***p < 0.005 (one-way ANOVA and Tukey's post-hoc test).