Different regulation of phospho-Rsk residues in HD knock-in mice and STHdhQ111/Q111 cells. Lysates from the striatum of 10-month old wild-type (HdhQ7/Q7) and knock-in (HdhQ111/Q111) mice (A) or from wild-type (STHdhQ7/Q7) and mutant (STHdhQ111/Q111) htt knock-in striatal cells (B) were subjected to western blot to analyze phosphor-Rsk (Ser-380; Ser-221), Rsk1, Rsk2 and tubulin protein levels. Results (mean ± SEM; n = 4-6) represent the ratio between phospho-Rsk levels and Rsk1 plus Rsk2 levels obtained by densitometric analysis of western blot data, and are expressed as a percentage of HdhQ7/Q7 (A) or STHdhQ7/Q7 (B) levels. Representative immunoblots are presented. All data were analyzed by Student's t-test. *p < 0.05, **p < 0.01 and ***p < 0.001 as compared with HdhQ7/Q7 mice (A) or STHdhQ7/Q7 cells (B).