Abstract: A method of identifying a compound which modulates the interaction between a PP1c and a regulatory subunit thereof, the method comprising determining whether a compound enhances or disrupts the interaction between (a) a PP1c or a fragment, variant, derivative or fusion thereof or a fusion of a fragment, variant or derivative and (b) a regulatory subunit which is able to bind to PP1c or a PP1c-binding fragment, variant, derivative or fusion of the subunit or a fusion of the fragment, variant or derivative. A method of affecting cellular metabolism or function, the method comprising administering to a cell (a) a compound which modulates the interaction between a PP1c and a regulatory subunit thereof or (b) a compound which mimics the effect of a regulatory subunit of PP1c or (c) a peptide capable of binding a PP1c and which affects the ability of PP1c to bind to a particular target and/or affects the regulation of PP1c activity, or a functional equivalent thereof.