AMF-R tubules concentrate in a pericentriolar microtubule domain after MSV transformation of epithelial MDCK cells.

Abstract

Autocrine motility factor receptor (AMF-R) is localized to an intracellular microtubule-associated membranous organelle, the AMF-R tubule. In well-spread untransformed MDCK epithelial cells, the microtubules originate from a broad perinuclear region and AMF-R tubules extend throughout the cytoplasm of the cells. In Moloney sarcoma virus (mos)-transformed MDCK (MSV-MDCK) cells, microtubules accumulate around the centrosome, forming a microtubule domain rich in stabilized detyrosinated microtubules. AMF-R tubules are quantitatively associated with this pericentriolar microtubule domain and the rough endoplasmic reticulum and lysosomes also co-distribute with the pericentriolar mass of microtubules. The Golgi apparatus is closely associated with the microtubule organizing center (MTOC) within the juxtanuclear mass of AMF-R tubules, and no co-localization of AMF-R tubules with the Golgi marker beta-COP could be detected by confocal microscopy. After nocodazole treatment and washout, microtubule nucleation occurs exclusively at the centrosome of MSV-MDCK cells, and only after microtubule extension to the cell periphery does the microtubule cytoskeleton reorganize to generate the pericentriolar microtubule domain after 30-60 min. AMF-R tubules dispersed by nocodazole treatment concentrate in the pericentriolar region in parallel with the reorganization of the microtubule cytoskeleton. MSV transformation of epithelial MDCK cells results in the stabilization of a pericentriolar microtubule domain responsible for the concentration and polarized distribution of AMF-R tubules.