Abstract
Cell-substrate contact formation is crucial for growth cone motility. By monitoring cell-substrate distance by reflection interference contrast microscopy, we found that growth cone maintained stable contacts at its central domain. In contrast, at the peripheral domain, we observed membrane ruffling with transient contact formation. We previously reported that β1 integrin, one of adhesive molecules, is incorporated into the basal membrane of growth cones by exocytosis. However, the relation between integrin incorporation and cell-substrate contact formation is not clear. To elucidate this, we monitored exocytic incorporation of fluorescent-labeled β1 integrin and contact formation in the growth cone. To observe exocytic events, we employed VAMP-pHluorin as a fluorescent probe to monitor intravesicular pH changes during exocytosis. Time lapse imaging showed that β1 integrin was incorporated into a restricted area where the growth cone formed stable contacts. At the peripheral domain, in contrast, exocytic event was not observed. In addition, approx. 50% of incorporated β1 integrins at the central domain went away from their original position. These results suggest that a half of incorporated β1 integrin contributes to form stable contacts at the central domain and that the other half could move to peripheral domain being involved in transient contacts formation. [Jpn J Physiol 54 Suppl:S144 (2004)]
