Direct interaction between the catalytic subunit of Protein Phosphatase 1 and pRb.

Background: The product of the retinoblastoma-susceptibility gene (pRb) is a substrate for Protein Phosphatase 1 (PP1). At mitotic exit, all three PP1 isoforms, alpha, gamma1 and delta, bind to pRb and dephosphorylate its Ser/Thr sites in a sequential and site-specific way. The pRb-C terminal has been reported to be necessary and sufficient for PP1alpha binding.

Reciprocally interacting domains of protein phosphatase 1 and focal adhesion kinase.

Protein phosphatase 1delta (PP1delta) localizes to focal adhesions and associates with the focal adhesion kinase (FAK). In the present work we used deletion mutants of PP1delta and FAK to detect their reciprocally interacting domains. Dissection of PP1delta indicated 194-260 as the shortest FAK-interacting domain among those tested.

Regulation of FAK Ser-722 phosphorylation and kinase activity by GSK3 and PP1 during cell spreading and migration.

In addition to tyrosine sites, FAK (focal adhesion kinase) is phosphorylated on multiple serine residues. In the present study, the regulation of two of these sites, Ser-722 (S1) and Ser-911 (S4), was investigated. Phosphorylation of S1 (but not S4) decreased in resuspended cells, and recovered during spreading on fibronectin, indicating adhesion-dependent regulation.