K252A, A POTENT INHIBITOR OF PROTEIN-KINASES, INHIBITS THE MIGRATION OF CEREBELLAR GRANULE CELLS IN-VITRO

In order to elucidate the cellular mechanisms of migrating neurons, we developed an assay system in vitro, using an aggregation culture of d eveloping granule cells from the rat cerebellum. This assay system all owed us to eliminate the effects of various factors other than neurons and to examine the direct effects of individual molecules on neuronal migration. In this assay system, we examined the effects of several p rotein kinase inhibitors on cerebellar granule cell migration, and rev ealed that K252a, an inhibitor of protein kinases and of the actions o f neurotrophins, inhibited the migration. Within 5 min after the addit ion of K252a to the culture medium, most of the migrating spindle-shap ed cells changed into non-migrating large and polygonal cells, which h ad many microspikes. Staining with rhodamine-phalloidin revealed the a ppearance of actin bundles that resembled stress fibers within these l arge cells. On the other hand, extension of neurites was not severely inhibited by the addition of K252a. These results suggest that the mig ration is regulated by a different mechanism from that of neurite grow th.