Cdk5 phosphorylates NMHC-B in SH-SY5Y cells. A. A Western blot showing a 200 kDa pSerCdk substrate band in undifferentiated and RA-differentiated SH-SY5Y cells. Phosphorylation of pSerCdk substrate is completely inhibited when cells are treated with 10 μM Roscovitine for 4 hours. B. A Western blot showing a pSerCdk antibody immunoprecipitated sample from SH-SY5Y cells probed with pSerCdk substrate antibody and with antibody to NMHC-B. Detection of the same band by both antibodies verifies that a 200 kDa band found in SH-SY5Y cells is NMHC-B. C. A Western blot showing pSerCdk substrate and p25 levels in control and in p25 transfected SH-SY5Y cells. Transfection with p25 does not increase pSerCdk substrate phosphorylation in SH-SY5Y cells. D. Densitometric quantification of pSerCdk phosphorylation in SH-SY5Y cells transfected with 8 μg p25 plasmid presented as % of control (mean ± SEM).