Regulation of protein kinase Fa (a transmembrane signal of insulin and epidermal growth factor) in the brain

Two forms of type-1 protein phosphatase activating factor (Fa) termed Fa1 and Fa2 have been identified in plasma membranes of pig brain. Fa1 is spontaneously active and trypsin-labile whereas Fa2 is inactive and trypsin-resistant. Phospholipid reconstitution studies further indicate that the Fa activity in the neutral phospholipids-reconstituted complex is spontaneously active and trypsin-labile whereas the Fa activity in the acidic phospholipids-reconstituted complex is trypsin-resistant and inactive. The results indicate that inactive Fa2 may have its catalytic domain interacted with negatively-charged phospholipids in brain membranes. This provides initial evidence for the regulation of protein kinase Fa (a transmembrane signal of insulin and epidermal growth factor) in the central nervous system.