Liprinα1 interacts with PP2A B56γ

Inhibition of the protein phosphatase 2A (PP2A) family of serine-threonine phosphatases contributes to human cell transformation. Depletion of PP2A complexes containing the PP2A B56 gamma regulatory subunit in immortalized human cells induces cell transformation in vitro. To examine the function of PP2A B56 gamma complexes, we applied tandem affinity purification and mass spectrometry to detect proteins that bind to PP2A B56 gamma. We identified liprin alpha 1 as a novel PP2A B56 gamma interacting protein. B56 gamma-liprin alpha 1 complexes are distinct from PP2A complexes containing B56 gamma. Consistent with this finding, liprin alpha 1 does not directly contribute to cell transformation. However, suppression of liprin alpha 1 by RNA interference alters cell morphology. These findings suggest a novel role for PP2A B56 gamma independent of its regulation of PP2A activity.