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Y H Ehrlich

Publications and source records attributed to Y H Ehrlich.

64 records · Page 4Linked to original sources
PubMed1978

Selective changes in the phosphorylation of endogenous proteins in subcellular fractions from cyclic AMP-induced differentiated neuroblastoma cells.

The endogenous phosphorylation of specific proteins was studied in subcellular fractions from proliferating and cAMP-induced differentiated neuroblastoma cells. Fractions containing nuclear, membrane-bound, and cytosolic proteins were incubated with [gamma-32P]ATP, in the presence and absence of added cyclic nucleotides. Phosphate incorporation into specific proteins was determined by slab-gel electrophoresis of sodium dodecyl sulfate-solubilized reaction products. Cytosol fractions from differentiated cells demonstrated a twofold increase in cAMP-dependent phosphorylation of a specific protein with apparent mol wt of 59,000 daltons and a comparable decrease in cAMP-independent phosphorylation of another protein (97,000). The nuclear fraction of differentiated cells showed an increase in the cAMP-independent phosphorylation of two nonhistone proteins (110,000 and 102,000). Membrane fractions from differentiated cells exhibited a differential decrease in endogenous phosphorylation of specific proteins. Selective alterations in the phosphorylation of specific proteins in various subcellular components may be important biochemical events associated with the increased levels of differentiated functions in neuroblastoma cells in culture.

Cell Differentiation↗
PubMed1977

Experiential input alters the phosphorylation of specific proteins in brain membranes.

The effects of a training experience that involves foot shock on the endogenous phosphorylation of membrane-bound proteins from brain were studied. Crude membrane fractions were prepared from the cerebral cortex and neostriatum of animals that had been sacrificed by quick freezing. In vitro incubation of the membranes with gamma-32P-ATP, follwed by SDS-gel electrophoresis of the phosphorylated substrates, revealed that the phosphorylation of two protein components (designated F and H-I) increased in preparations from animals that were subjected to a training experience 24 hr prior to sacrifice. These effects were greater in preparations from the neostriatum than from the cerebral cortex, and were observed in experiments using both rats and mice. Although all trained animals showed a high phosphorylation of bands F and H-I, control animals showed a greater variability in the phosphorylation of these bands. The results indicate that the phosphorylation of specific proteins may play a mediatory role in the processing of experiential information.

Adenosine Triphosphate↗
PubMed1975

Endogenous phosphorylation of four cerebral cortical membrane proteins: role of cyclic nucleotides, ATP and divalent cations.

Endogenous phosphorylation of 4 membrane-bound protein components of cerebral cortex was studied in vitro. Cyclic AMP was shown to stimulate phosphorylation to a major extent in protein components designated D, E and G, but to a minor extent in protein component F. The time course of phosphorylation of each of these components is affected differently by (a) the presence of cyclic nucleotides or zinc ions and (b) the concentration of ATP and magnesium ions in the reaction mixture. Although a different membrane preparation was used here than by Ueda et al., molecular weight determination and response to divalent cations, magnesium and zinc, suggest that components D and E may be the same as their proteins I and II. The newly described phosphoproteins, F and G, are respectively the least and most stimulated by the addition of cyclic AMP. Under certain conditions phosphate content in protein E can be increased by cyclic AMP and decreased by cyclic GMP.23Author

Adenosine Triphosphate↗
PubMedDate not supplied

Effects of decapitation-stress on the phosphorylation of cortical membrane proteins.

The endogenous phosphorylation of membrane-bound proteins was studied in preparations from the cerebral cortex of rats sacrificed by immersion in liquid nitrogen or by decapitation. Compared to quick-frozen rats, samples from decapitated animals demonstrated a two-fold increase in 32P-phosphate incorporation into specific protein bands with apparent molecular weights of 56K, and 52K (designated E1 and E2) and a decreased incorporation into a phosphoprotein of 47K (designated F). The phosphorylation of two proteins (78K and 34K) in membranes from decapitated rats was found to be highly stimulated by exogenously added cyclic AMP. On the other hand, the phosphorylation of specific protein bands in preparations from quick frozen rats was minimally affected by addition of cyclic AMP. The results indicate that conditions which lead to increases in cyclic AMP levels in the brain in situ induce specific changes in phosphorylative activity, and these can be detected by assaying isolated membrane fragments in vitro.

Animals↗
PubMedDate not supplied

Ecto-protein kinase activity on the external surface of neural cells.

ATP is secreted in association with neurotransmitters at certain synapses and neuromuscular junctions. Extracellular ATP is known to exert potent effects on the activity of cells in the nervous system, where it can act as a neurotransmitter or as a modulator regulating the activity of other neurohormones. We have suggested that such modulation may involve the activity of extracellular protein phosphorylation systems. It is well known that intracellular protein kinases are important in the regulation of various neuronal functions, but protein kinases which use extracellular ATP to phosphorylate proteins localized at the external surface of the plasma membrane (ecto-protein kinases) have not been demonstrated in neuronal cells. Here we present direct evidence for the existence of an ecto-protein kinase and demonstrate endogenous substrates for its activity at the surface of intact neural cells. The phosphorylation of one of these surface proteins is selectively stimulated during cell depolarization. In addition, neuronal cell adhesion molecules (N-CAMs) appear to be among the substrates of ecto-protein kinase activity. These results suggest a role for surface protein phosphorylation in regulating specific functions of developing and mature neurones.

Adenosine Triphosphate↗