Differential localisation of tyrosinated, detyrosinated, and acetylated α‐tubulins in neurites and growth cones of dorsal root ganglion neurons

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Abstract
The comparative distribution of tyrosinated, detyrosinated, and acetylated α‐tubulins was examined in neurites of rat dorsal root ganglion neurones in culture using immunofluorescence microscopy. Phase contrast observations of single neurones revealed that the neurites were actively motile, and rhodamine phalloidin staining of actin filaments showed the extent of lamellopodia and microspike projections from the growth cones. From double‐labelling experiments using antibodies against tyrosinated, detryrosinated, or acetylated α‐tubulin, it was found that the three different isoforms were differentially localised in neurites and growth cones. Detyrosinated and acetylated forms of α‐tubulin were in the main restricted to the neurites extending no further than the base of the growth cones. Tyrosinated α‐tubulin was, however, distributed throughout the body of the growth cone and into the base of some microspikes. Following treatment with taxol to promote microtubule assembly, detyrosinated and acetylated α‐tubulins were found to be colocalised with tyrosinated α‐tubulins throughout the growth cones of all cells examined. These results would be consistent with axonal transport of tyrosinated α‐tubulin followed by assembly in the growth cone and subsequent detyrosination and acetylation. In addition the presence of unmodified α‐tubulin in the growth cone may be necessary for the provision of labile microtubules for growth cone motility and extension.