Widespread occurrence of "87 kDa," a major specific substrate for protein kinase C.

Abstract

An 87-kDa phosphoprotein, identified previously as a major, specific substrate for Ca2+/phospholipid/diacylglycerol-dependent protein kinase (protein kinase C) in broken cell preparations from rat brain, has been characterized with respect to its species, tissue, and subcellular distribution. A similar protein was present in monkey, human, mouse, and bovine brain and in Torpedo californica electric organ. The protein was also identified in a variety of nonneuronal rat and bovine tissues. The rat protein had an apparent molecular mass 4-7 kDa lower, and was slightly more acidic, than the protein in bovine tissues. The 87-kDa proteins from various bovine tissues were identical by the following criteria: each was phosphorylated by exogenous protein kinase C, was ofcomparable molecular mass, generated multiple spots within the pH range of 4.4-4.9 upon isoelectric focusing, yielded identical patterns upon digestion with Staphylococcus aureus V8 protease, and was recognized by a specific 87-kDa antiserum. The relative concentrations of the 87-kDa protein in bovine tissues were highest in brain, spleen, and lung, moderate in testis, pancreas, adrenal, kidney, and liver, and lowest in heart and skeletal muscle. In the brain, the 87-kDa protein was concentrated in the synaptosomal membrane and in the cytosol. The membrane-bound protein was extractable with nonionic detergents but not with NaCI. This species, tissue, and subcellular distribution of the 87-kDa protein is similar to that of protein kinase C.

Insulin increases membrane protein kinase C activity in rat diaphragm

“…We therefore analysed the insulin effect in the separated fractions. Since both histone H2B and histone III-S can be phosphorylated by a number of protein kinases, a brain enriched 87 kDa protein which appears to be a specific substrate for protein kinase C [14,15,17] was used as substrate in these experiments. Fig.3 and table 1 show that membrane extracts from rat diaphragm phosphorylated the 87 kDa protein in a manner dependent upon calcium and phosphatidylserine.…”

Eicosanoid Activation of Protein Kinase C ϵ

“…This band corresponds to a well known PKC substrate (66), the adhesion site protein MARCKS, for the following reasons. (a) In previous experiments, two-dimensional gel analysis revealed a single spot at 87 kDa, with the pI (4.2) of MARCKS (37); (b) the 87-kDa phosphoprotein remained soluble in an acetic acid extraction (67) 2 ; (c) Western blots of GCP proteins probed with an antibody to MARCKS indicated co-migration of the radiolabeled 87-kDa band with MARCKS; (d) immunoprecipitation with a MARCKS antibody specifically isolated the thrombin-stimulated phosphoprotein.…”

The glutamatergic nerve terminal

“…MARCKS is a major substrate for PKC in a variety of cells (Albert et al, 1986). It exists in soluble and membranebound forms, and the latter may be myristoylated to provide a hydrophobic attachment to the membrane.…”

“…In synaptosomes there are two major substrates, a growth-associated protein (GAP-43, also named neuromodulin3, pp46, F1, B50; Gispen, 1985;DeGraan et al, 1989;Dekker et al, 1990a) and the myristoylated, alanine-rich, calmodulin-kinase-associated protein (MARCKS), a filamentous protein also known as the 87-kDa protein (Albert et al, 1986;Wang et al, 1989) although, as will be discussed below, there is no evidence that phosphorylation of either protein is directly responsible for the regulation of glutamate release.…”