Down-regulation of spinophilin in lung tumours contributes to tumourigenesis.

The scaffold protein spinophilin (Spn, PPP1R9B) is one of the regulatory subunits of phosphatase-1a (PP1), targeting it to distinct subcellular locations and to its target. Loss of Spn reduces PPP1CA levels, thereby maintaining higher levels of phosphorylated pRb. This effect contributes to an increase in p53 activity.