Distribution of detyrosinated microtubules in motile NRK fibroblasts is rapidly altered upon cell‐cell contact: Implications for contact inhibition of locomotion

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Abstract
Fibroblasts migrating into an experimental wound contain an extensive array of detyrosinated microtubules (Glu MTs) oriented in the direction of migration, whereas nonmotile cells in the interior of a monolayer contain Glu MTs that are primarily coiled around the nucleus. To determine the role of cell-cell contact in the formation of these distinct arrays of Glu MTs, we studied the distribution of Glu MTs by immunofluorescence in NRK fibroblasts that had been fixed at different intervals after they had established contact with other cells. Time-lapse video recordings were made of the contacting cells to provide a record of cellular behavior. In motile cells that became completely surrounded by virtue of contact with other cells, Glu MTs were found mostly coiled around the nucleus. The proportion of cells whose Glu MTs extended to the original leading edge decreased dramatically after the cells had been surrounded for 10 min or more. At earlier times, when the contact was confined to a portion of the cell margin, Glu MTs were absent from the area behind the contact site, yet were still oriented toward the noncontacting and ruffling margins. The contact-induced alteration of Glu MTs was not due to the cessation of forward locomotion of cells per se, since immobilization of cells with cytochalasin D did not cause a dramatic change in Glu MTs. That cell-cell contact also specifies the type of Glu MTs formed in cells was shown by experiments in which MTs were regrown following complete depolymerization with nocodazole. The remodeling of Glu MTs during cell-cell contact may be involved in cellular repolarization during contact inhibition of locomotion and will be a useful marker for further dissecting the molecular events of contact inhibition of motility.