GSK3 promotes phosphorylation cascades of the DP CT tail. (A) GSK3 cascade 1 (solid arrows) and 2 (dotted arrows) in WT, S2849G (red), and R2834H (*) DP. (B) NaCl- or LiCl-treated WT DP S-tag (DP CT) cell lysates were assessed by phos-tag immunoblot analyses (red arrow, 36 kD). (C and C′) Phosphorylation of DP S-tag (DP CT) point mutations, S2845A and T2853A, assessed by immunoblotting. Red arrows mark GSK3 phosphorylation of DP. Densitometry quantification of three independent experiments. *, P < 0.001. Error bars indicate SEM. (D and D′) NaCl-, LiCl-, DMSO-, or Ly-294,002–treated WT, S2845A, or T2853A DP S-tag (DP CT) lysates, assessed by immunoblotting. Densitometry quantification of three independent experiments. *, P < 0.001. Error bars indicate SEM. (E and E′) DMSO-, KT 5720-, Gö 6976-, or LiCl-treated DP S-tag (DP CT) lysates, assessed by immunoblotting (red arrow, 36 kD). Densitometry quantification of three independent experiments. Error bars indicate SEM. (F) DP S-tag (DP CT) expressing HEK 293 cells were treated with kinase inhibitors targeting CKI, CKII, MNKI, atypical PKC, and DYRK kinases, assessed by immunoblotting. (G) Control, 40 mM LiCl-, and PMA-treated SCC9s, assessed by immunofluorescence. Bars, 10 µm. (H and H′) GSK3 interactions with S2849G and WT DP S-tag (DP CT) in HEK 293 cells were examined after S-tag pull-down analyses where RIPA lysates (input) and pull-down products were analyzed by immunoblotting and quantified by densitometry. *, P < 0.03. Error bars indicate SEM.