Protein phosphatase inhibitor-1 (also designated inhibitor of protein phospha-tase 1, IPP-1 and I-1) plays a role in regulating the phosphorylation of other proteins, and is itself phosphorylated by a cyclic AMP-dependent protein kinase at Threonine 35. In addition, the proline-directed kinases Cdk1, Cdk5, and mitogen-activated protein kinase (MAPK) mediate in vitro phosphorylation of IPP-1 at the phylogenetically conserved position Serine 67. In striatal tissues, glutamate-dependent regulation of N-methyl-d-aspartic acid-type channels influences IPP-1 phosphorylation at Ser 67. The localization and expression of IPP-1 suggests that it may play discrete roles in certain regions and developing stages of the brain, independent of the regulation of protein phosphatase type 1 (PP-1). PP-1 binds to both phosphorylated and dephosphorylated IPP-1. Conversion of PP-1 to a Mn++-dependent state appears to play a role in its regulation by IPP-1. IPP-1 attenuates the activity of glycogen phosphorylase and is thought to be important in the hormonal control of glycogen metabolism.
I-1; inhibitor-1; IPP-1; PP1 inhibitor 1; Protein phosphatase 1 regulatory subunit 1A; protein phosphatase 1, regulatory (inhibitor) subunit 1A; Protein phosphatase inhibitor 1; protein phosphatase inhibitor-1