DARPP-32 (dopamine and cAMP-regulated phosphoprotein,Mr32,000) is a membrane protein in the bovine parathyroid

Abstract
A distinct form of DARPP‐32, a protein phosphatase‐1 inhibitor, has been identified in bovine calf parathyroid glands. Immunoblot analysis of parathyroid tissue revealed a 32 kDa protein present predominantly in a particulate fraction; it remained particulate after treatment with 1.0 M NaCl or 0.1 M Na2CO3. Metabolic labeling of parathyroid cells with mevalonolactone demonstrated that DARPP‐32 is isoprenylated. Immunocytochemical localization studies demonstrated that DARPP‐32 is present in vesicles throughout the cytoplasm of parathyroid cells, and that protein phosphatase‐1γ is concentrated in the region of the plasma membrane. Thus, in contrast to the predominately soluble form of DARPP‐32 that has been characterized in selected areas of the central nervous system, the parathyroid form is tightly associated with intracellular membranes.