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Biochemistry of an Olfactory Purinergic System: Dephosphorylation of Excitatory Nucleotides and Uptake of Adenosine
Author(s) -
TrapidoRosenthal Henry G.,
Carr William E. S.,
Gleeson Richard A.
Publication year - 1987
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1987.tb10008.x
Subject(s) - purinergic receptor , adenosine , dephosphorylation , nucleotide , biochemistry , purinergic signalling , biology , adenosine diphosphate , adenine nucleotide , excitatory postsynaptic potential , adenosine triphosphate , adenosine monophosphate , extracellular , biophysics , phosphatase , receptor , adenosine receptor , enzyme , platelet , platelet aggregation , gene , immunology , agonist
The olfactory organ of the spiny lobster, Panu‐lirus argus , is composed of chemosensory sensilla containing the dendrites of primary chemosensory neurons. Receptors on these dendrites are activated by the nucleotides AMP, ADP, and ATP but not by the nucleoside adenosine. It is shown here that the lobster chemosensory sensilla contain enzymes that dephosphorylate excitatory nucleotides and an uptake system that internalizes the nonexcitatory dephosphorylated product adenosine. The uptake of [ 3 H]‐adenosine is saturable with increasing concentration, linear with time for up to 3h, sodium dependent, insensitive to moderate pH changes and has a K m of 7.1 μ M and a V max of 5.2 fmol/sensillum/min (573 fmol/μg of protein/min). Double‐label experiments show that sensilla dephosphorylate nucleotides extracellularly; 3 H from adenine‐labeled AMP or ATP is internalized, whereas 32 P from phosphate‐labeled nucleotides is not. The dephosphorylation of AMP is very rapid; 3 H from AMP is internalized at the same rate as 3 H from adenosine. Sensillar 5′‐ectonucleotidase activity is inhibited by ADP and the ADP analog α,β‐methylene ADP. Collectively, these results indicate that the enizymes and the uptake system whereby chemosensory sensilla of the lobster inactivate excitatory nucleotides and clear adenosine from extracellular spaces are very similar to those present in the internal tissues of vertebrates, where nucleotides have many neuroactive effects.