Evidence that synaptosomal high-affinity carriers for amino acid neurotransmitters are glycosylated
The effect of removal of surface sialic acid from synaptosomes on the high-affinity, Na/sup +/-dependent uptake systems for amino acid neurotransmitters was evaluated. Synaptosomes from rat forebrain were preincubated with neuraminidase from Vibrio cholerae for 20 min at 34/sup 0/. After washing and resuspension, their ability to transport /sup 14/C-GABA and the acidic amino acid, /sup 3/H-aspartate was studied. Pretreatment with neuraminidase resulted in a concentration-dependent inhibition of the uptake of both amino acids while the influx of /sup 3/H-L-leucine was unaffected. Inhibition was a function of the amount of sialic acid released from membranes. The analysis of the kinetic parameters of amino acid uptake revealed that inhibition resulted from a decrease of Vmax without any change in the Km. Neither the synaptosomal energy levels nor the internal concentration of potassium ions was affected by the pretreatment with neuraminidase. The maximum accumulation ratios for both amino acids remained largely unaltered. It is concluded that the GABA and acidic amino acid transporters are glycosylated and that sialic acid is involved in the operation of carrier proteins directly and not through modification of the driving forces responsible for amino acid transport.
- Research Organization:
- Univ. of Pennsylvania, Philadelphia
- OSTI ID:
- 6022412
- Report Number(s):
- CONF-870644-; TRN: 87-034066
- 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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Related Subjects
AMINOBUTYRIC ACID
MEMBRANE TRANSPORT
METABOLISM
ASPARTIC ACID
NERVES
BIOCHEMISTRY
SIALIC ACID
BIOCHEMICAL REACTION KINETICS
AFFINITY
BRAIN
CARBON 14 COMPOUNDS
INHIBITION
LEUCINE
O-GLYCOSYL HYDROLASES
RATS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
AMINO ACIDS
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BODY
CARBOHYDRATES
CARBOXYLIC ACIDS
CENTRAL NERVOUS SYSTEM
CHEMISTRY
DRUGS
ENZYMES
GLYCOSYL HYDROLASES
HYDROLASES
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MAMMALS
MONOSACCHARIDES
NERVOUS SYSTEM
NEUROREGULATORS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
REACTION KINETICS
RODENTS
SACCHARIDES
VERTEBRATES
550501* - Metabolism- Tracer Techniques