Thrombin receptor on rat primary hippocampal neurons: coupled calcium and cAMP responses.
We have tested the hypothesis that hippocampal neurons respond to thrombin via a neuronal thrombin receptor. A human neuroblastoma cell line, SK-N-SH, known to be thrombin responsive morphologically, responded both to thrombin and thrombin receptor agonist peptide (TRAP 42-55) with elevation of intracellular calcium. In Western blots of membranes from SK-N-SH cells and cultured rat hippocampal neurons using an antibody against the N-terminal peptide of the human thrombin receptor, putative receptor proteins of 66 and 47 kDa were detected in both cells. Neurons were treated with thrombin and TRAP 42-55 (TRAP-14) to determine their effects on intracellular levels of calcium and cAMP. Only 10% of the neurons showed a rapid response to thrombin, but most responded rapidly to agonist peptide with a prolonged elevation of intracellular free calcium. Neuronal cAMP levels were decreased by 40% after 24 h thrombin treatment. This decrease in cAMP level could be blocked by both the Gi-protein inhibitor, pertussis toxin, and the thrombin inhibitor, hirudin, suggesting a possible involvement of Gi-protein-coupled receptor activation. Furthermore, rapid calcium and cAMP responses were apparently induced by pre-treatment of neurons with thrombin for 24 h and subsequent washout. In summary, these data indicate that rat primary hippocampal neurons have thrombin receptors whose responses to thrombin apparently are up-regulated by 24 h thrombin pre-treatment. These results may have implications for synaptic remodeling, learning and memory.
Yang
Y
Y
Department of Medical Microbiology and Immunology, Southern Illinois University School of Medicine, Springfield 62794-1220, USA. gbrewer@siumed.edu
Akiyama
H
H
Fenton
J W
JW
Brewer
G J
GJ
D000818:Animals; D001667:Binding, Competitive / Q000502:physiology; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology*; D006801:Humans; D008565:Membrane Proteins / Q000032:analysis; D009447:Neuroblastoma; D009474:Neurons / Q000737:chemistry* / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D018179:Receptors, Thrombin / Q000819:agonists / Q000032:analysis*; D013917:Thrombin / Q000494:pharmacology; D013997:Time Factors; D014407:Tumor Cells, Cultured / Q000737:chemistry
D008565:Membrane Proteins; D010446:Peptide Fragments; D018179:Receptors, Thrombin; C072032:thrombin receptor peptide (42-55); D000242:Cyclic AMP; D013917:Thrombin; D002118:Calcium