DARPP-32 (DOPAMINE AND CAMP-REGULATED PHOSPHOPROTEIN, M(R)-32,000) ISA MEMBRANE-PROTEIN IN THE BOVINE PARATHYROID

A distinct form of DARPP-32, a protein phosphatase-1 inhibitor, has be en identified in bovine calf parathyroid glands. Immunoblot analysis o f parathyroid tissue revealed a 32 kDa protein present predominantly i n a particulate fraction; it remained particulate after treatment with 1.0 M NaCl or 0.1 M Na2CO3. Metabolic labeling of parathyroid cells w ith mevalonolactone demonstrated that DARPP-32 is isoprenylated. Immun ocytochemical localization studies demonstrated that DARPP-32 is prese nt in vesicles throughout the cytoplasm of parathyroid cells, and that protein phosphatase-ly is concentrated in the region of the plasma me mbrane. Thus, in contrast to the predominately soluble form of DARPP-3 2 that has been characterized in selected areas of the central nervous system, the parathyroid form is tightly associated with intracellular membranes.