Colocalisation of acetylated microtubules, glial filaments, and mitochondria in astrocytes in vitro

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Abstract
We have recently shown that acetylated α-tubulin containing microtubules (acety1-MTs; labeled by antibody 6-11B-1) constitute a cold-stable subset of the microtubule network of nonneuronal cells in rat primary forebrain cultures [Cambray-Deakin and Burgoyne: Cell Motil. 8(3):284–291, 1987b]. In contrast, tyrosinated α-tubulin containing MTs (tyr-MTs; labeled by antibody YL1/2) are cold-labile. Here we have examined the distribution of acety1-MTs and tyr-MTs in cultures of newborn rat forebrain astrocytes and simultaneously investigated the distribution of mitochondria and glial filaments. In double-label immunofluorescence experiments a marked colocalisation of acetyl-MTs and glial filament bundles was observed. Tyr-MTs did not show a similar colocalisation with glial filament bundles. Furthermore, the distribution of mitochondria closely followed that of the acetyl-MT and glial filament bundles. When cells were exposed to short-term (30-min) treatments with MT-disrupting agents such as colchicine and nocodazole, the tyr-MT network was removed but the distributions of acetyl-MTs, glial filaments, and mitochondria were unchanged. Increased exposure to colchicine (9–16 hr) caused a progressive disruption of the acetyl-MTs and the collapse of glial filaments and mitochondria to the perinuclear region. These results suggest that acetyl-MTs and glial filaments but not tyr-MTs may be involved in the intracellular transport of organelles and/or in the control of their cytoplasmic distribution.