Subject(s)
Cerebellum/metabolism , Kainic Acid/metabolism , Receptors, Neurotransmitter/metabolism , Animals , Cerebellum/ultrastructure , Chickens , Cloning, Molecular , Immunohistochemistry , Molecular Weight , Neuroglia/metabolism , Receptors, Kainic Acid , Receptors, Neurotransmitter/chemistry , Receptors, Neurotransmitter/geneticsABSTRACT
Kainate receptors mediate some of the excitatory transactions carried out in the central nervous system by the neurotransmitter glutamate. They are involved in neurotoxicity, possibly in neurodegenerative disorders and it has been suggested that they have a role in long-term potentiation. Kainate receptors are present both on neuronal and glial cell membranes where they regulate the gating of a voltage-independent ion channel. Nothing is known about their molecular structure. Taking advantage of the unusually high abundance of 3H-kainate binding sites in the chick cerebellum, we have isolated an oligomeric protein that displays a pharmacological profile similar to that of a kainate receptor, and have demonstrated, using the monoclonal antibody IX-50, that this protein is composed of a single polypeptide of Mr 49,000 which harbours the specific kainate recognition site. The structure of this kainate binding protein (KBP) is also of interest because of its exclusive cerebellar localization on Bergmann glial membrane in close proximity to established glutamatergic synapses. We now report the isolation of the complementary DNA containing the complete coding region of the kainate binding protein. The predicted structure of the mature protein has four putative transmembrane domains with a topology analogous to that found in the superfamily of ligand-gated ion channels. This raises the possibility, that kainate binding protein may form part of an ion channel and may be a subunit of a kainate subtype of glutamate receptor.
Subject(s)
Carrier Proteins/isolation & purification , Cerebellum/analysis , Kainic Acid/metabolism , Receptors, Neurotransmitter/analysis , Receptors, Neurotransmitter/isolation & purification , Amino Acid Sequence , Animals , Base Sequence , Carrier Proteins/genetics , Chickens , Cloning, Molecular , DNA/genetics , DNA/isolation & purification , Ion Channels , Macromolecular Substances , Molecular Sequence Data , Nucleic Acid Hybridization , Receptors, Glutamate , Receptors, Kainic Acid , Receptors, Neurotransmitter/genetics , Sequence Homology, Nucleic AcidABSTRACT
We have examined the relationship between induction of interferon (IFN) and prostaglandin E (PGE) production by poly(rI).poly(rC) in cultured human foreskin fibroblasts (FS11). Hydrocortisone and dexamethasone (2 . 5 x 10(-7) M), which are known inhibitors of PGE synthesis, significantly decreased the induction of both IFN and PGE in IFN-pretreated (primed) cells. Desoxycorticosterone, progesterone and estradiol were devoid of this activity. Hydrocortisone also blocked the induction of IFN by double-stranded RNA (dsRNA), cycloheximide and actinomycin D in FS11 cells. Arachidonic acid overcame the inhibitory effect of hydrocortisone on PGE production, but failed to restore IFN production in the presence of the steroid. Moreover, the prostaglandin synthetase inhibitors, indomethacin, aspirin and flufenamic acid, did not change IFN production by dsRNA in primed FS11 cells, although prostaglandin synthesis was abolished. Although the induction of IFN and PGE by poly(rI).poly(rC) might be consequences of the same initial event in the cell, the accumulation of PGE does not seem to have a regulatory effect on the synthesis of IFN in this system.
