THE THROMBIN RECEPTOR IN THE NERVOUS-SYSTEM

Neurite retraction and reversal of astrocyte stellation triggered by t he serine protease thrombin are receptor-mediated events, This article summarizes the current knowledge about the cellular effects that are induced by thrombin and its receptor in neural cells, The data present ed show that the thrombin receptor messenger RNA is expressed in cultu red astrocytes and that the reversal of stellation caused by thrombin in these cells is prevented by the protein kinase inhibitor staurospor ine, Peptides based in sequence on the tethered ligand domain of the t hrombin receptor were shown to mimic the effect of thrombin in most sy stems investigated, Platelets of some species, however, aggregate only in response to thrombin but not to the peptides, This observation is confirmed here, Rodent receptor-activating peptides did not cause aggr egation of rat or mouse platelets, In contrast, all peptides triggered reversal of stellation in rat astrocytes and neurite retraction in mo use neuroblastoma cells, supporting the proposed mechanism of cleavage -induced receptor activation in neural cells, Finally, evidence is pre sented that serum withdrawal causes a decrease in the amount of the th rombin receptor mRNA in different types of neuronal cells, The possibl e role played by the thrombin receptor in the nervous system is discus sed.