Regulation of GABA-modulin phosphorylation and GABA receptor binding by excitatory amino acids
Primary cultures of cerebellar granule cells phosphorylate numerous proteins including GABA-modulin (GM), which is a putative allosteric modulator of GABA receptors. Cell depolarization and treatment with dicarboxylic excitatory amino acids, which activate PI turnover, Ca/sup 2 +/ influx and guanylate cyclase in granule cells increase the phosphorylation of specific proteins. To determine GM phosphorylation by endogenous protein kinases in living granule cell cultures, GM was isolated by immunoprecipitation and reverse-phase HPLC. High K/sup +/, veratridine, glutamate and NMDA treatment stimulated GM phosphorylation over 2-fold. This increase was abolished by the absence of extracellular Ca/sup 2 +/ and was antagonized by Mg/sup 2 +/ ions and by AVP. The excitatory amino acid action was mimicked by phorbol esters but not by forskolin or by cGMP, and thus may be mediated by an activation of protein kinase C (PKC). Moreover, excitatory amino acids increase /sup 3/H-labelled phorbol ester binding sites in granule cell membrane. The same cultures, treated with glutamate or kainate, showed a 50-fold greater efficacy of muscimol for the stimulation of benzodiazepine (BZ) binding. These data-suggest that excitatory amino acid stimulation of neurons triggers PKC translocation and the activated enzyme phosphorylates GM. The extent of GM phosphorylation may regulate the coupling between GABA and BZ binding sites.
- Research Organization:
- Institute for the Neurosciences, Washington, DC
- OSTI ID:
- 6065410
- Report Number(s):
- CONF-870644-; TRN: 87-037631
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 46:6; Conference: 78. annual meeting of the American Society of Biological Chemists conference, Philadelphia, PA, USA, 7 Jun 1987
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
AMINOBUTYRIC ACID
RECEPTORS
PHORBOL ESTERS
BIOLOGICAL EFFECTS
PHOSPHOTRANSFERASES
ENZYME ACTIVITY
PROTEINS
PHOSPHORYLATION
BIOCHEMICAL REACTION KINETICS
AMINO ACIDS
CALCIUM COMPOUNDS
CATIONS
CELL CULTURES
ENZYME IMMUNOASSAY
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
AUTONOMIC NERVOUS SYSTEM AGENTS
CARBOXYLIC ACIDS
CARCINOGENS
CHARGED PARTICLES
CHEMICAL REACTIONS
DRUGS
ENZYMES
ESTERS
IMMUNOASSAY
IONS
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MEMBRANE PROTEINS
NEUROREGULATORS
ORGANIC ACIDS
ORGANIC COMPOUNDS
PHOSPHORUS-GROUP TRANSFERASES
REACTION KINETICS
TRANSFERASES
560300* - Chemicals Metabolism & Toxicology
550201 - Biochemistry- Tracer Techniques