Proteins of fast axonal transport in the regenerating hypoglossal nerve of the rat

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Abstract
The composition of proteins conveyed by fast axonal transport in growing or regenerating axons is different from that of intact, mature axons. Consistent alterations have been observed in several different types of neurons, but adult peripheral axons (rabbit hypoglossal motoneurons) seemed to be exceptions because during their regeneration there was no increased labelling of a 23 kilodalton (kD) protein associated with the growth state. We examined the composition of fast-transported proteins, labelled by application of [35S]methionine to the hypoglossal nuclei, in intact and regenerating hypoglossal nerves of the rat. Using one- and two-dimensional electrophoresis we detected both increases and decreases in the labelling of specific polypeptides during regeneration. In particular, there was increased labelling of a 23 kD polypeptide. Changes were maximal 7 days after axotomy and subsided thereafter, coincident with reinnervation of the tongue. We conclude that hypoglossal axons show the same changes in transported protein composition which are characteristic of the growth state in other axons. Thus, we have strengthened the correlation between the growth state and changes in synthesis of a set of polypeptides of unknown function.