CDK5 and Parkinson disease: While we observed increased phosphorylation of spinophilin at Ser17, a CDK5 site, in animal models of PD, it does not appear that increased phosphorylation at this site is responsible for the alterations in the spinophilin/NF-M association, as mutation of this site to an alanine did not rescue CDK5 activity-dependent decreases in the interaction between spinophilin and NF-M.