Elsevier

Brain Research

Volume 450, Issues 1–2, 31 May 1988, Pages 60-68
Brain Research

Research report
Role of microtubules in the cytoplasmic compartmentation of neurons. II. Endocytosis in the growth cone and neurite shaft

https://doi.org/10.1016/0006-8993(88)91544-2Get rights and content

Abstract

We investigated the role of microtubules in the compartmentation of motility and endocytosis in the neurite shaft and growth cone of cultured chick sensory neurons. As reported previously by Letourneau and Ressler (J. Cell Biol., 98 (1984) 1355–1362), stimulating microtubule polymerization with taxol inhibits growth cone motility. In neurons that had grown for 18–30 h, taxol treatment caused growth cones to round up forming an obvious varicosity (taxol bulb) at the termina. Removal of taxol allowed nearly immediate resumption of cortical motility in all 17 neurons observed by time-lapse videomicroscopy. However, only one of the 17 neurites was observed to elongate measurably even after 5 h of observation. In 14 cases taxol was rinsed out and the concentration of nerve growth factor was increased 10x, 1114 neurites retracted within the next hour. Endocytic activity was investigated by incubating control and taxol treated neurons in either cationized ferritin or horseradish peroxidase for 30 min. The number and area of label-containing vesicles was measured along with the total area of the growth cone or taxol bulb. We found that taxol treatment caused a 7-fold decrease in the ratio of the area of the labeled vesicles to the area of growth cone or taxol bulb. Conversely, in neurite shafts, normally relatively quiescent with respect to endocytosis, those regions devoid of microtubules in both control and nocodazole-treated cells contained a high concentration of label-containing vesicles. We conclude that the presence of microtubules plays a role in regulating endocytic activity by the overlying cell cortex. We speculate that this could be due either to transport activity mediated by microtubiles or to cortical stabilization by microtubules.

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