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ANALYSIS OF PROTEINS UNDERGOING AXONAL TRANSPORT IN NIGRO‐STRIATAL NEURONS IN THE RAT
Author(s) -
Singh V. K.,
Fibiger H. C.,
Mcgeer E. G.,
McGeer P. L.
Publication year - 1974
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1974.tb12187.x
Subject(s) - axoplasmic transport , caudate nucleus , chemistry , leucine , substantia nigra , homogenization (climate) , putamen , striatum , biochemistry , anatomy , endocrinology , biology , dopamine , amino acid , biodiversity , ecology , dopaminergic
— An analysis of proteins undergoing axonal transport in nigro‐striatal neurons, after the stereotaxic injection of [ 3 H]leucine into the substantia nigra of rat brain was performed. As early as 6 h after the injection [ 3 H]proteins appeared in the caudate‐putamen. The maximum accumulation was at 5 days and there was still residual protein radioactivity present at 30 days. About 70 per cent of the total radioactive protein in the caudate‐putamen was solubilized by homogenization in 0–5%, (v/v) Triton X‐100 and remained in the supernatant on centrifuging for 1 h at 100,000 g. The supernatant fraction, when chroma‐tographed on a DEAE‐cellulose column, was resolved into four protein peaks (A, B. C and D) which were found to be labelled differently as a function of time after the injection of [ 3 H]leucine. Peak A was substantially labelled in a first phase (6–24 h) and reached its maximum in a second phase (5 days). The proteins comprising this peak appeared to undergo both fast and slow axonal transport. Although some labelling in peak B was evident at 6 h, maximal activity did not occur until 5 days. No radioactivity could be detected in peaks C and D at 6 h. Maximal labelling of these two peaks also occurred at 5 days. These data suggest that the proteins of peaks B, C and D were transported primarily by slow axoplasmic flow. The radioactive protein peaks A and B from the second phase of the transport were excluded from a Sephadex G‐200 column, pointing to their high molecular weights (13,000–200,000). Peak B. which had the highest specific radioactivity (c.p.m./mg protein) at 5 days, contained a significant level of tyrosine hydroxylase, an important component of dopaminergic neurons.