Journal of Neuroscience, Vol 4, 868-879, Copyright © 1984 by Society for Neuroscience
Olfactory marker protein: turnover and transport in normal and regenerating neurons
RM Kream and FL Margolis
A 19,000-dalton acidic protein designated olfactory marker protein (OMP) is
a cell-specific marker of mature olfactory chemosensory neurons. Intranasal
irrigation of mouse olfactory epithelium with [35S]methionine labeled OMP
to high specific activity. Turnover and transport characteristics of
35S-labeled OMP were compared to those of 35S-labeled global cytosol
protein in groups of young, adult, and Triton-treated adult mice. The
latter contained primarily large numbers of regenerating olfactory neurons.
In olfactory epithelium of young and Triton-treated mice, the specific
activity of OMP was three times that of global cytosol protein, whereas in
adults the two measures were equal. In all three groups, however, the rate
of degradation of OMP was roughly equal to that of cytosol protein (T1/2 =
5 to 6 days). By contrast, differences in T1/2 for OMP decline in the bulb
of adult, young, and Triton-treated adult mice were highly significant
(T1/2's of 9.3, 6.1, and 4 to 5 days, respectively; p = 0.001). The
specific activity of [35S]methionine incorporated in OMP exceeded that of
the free amino acid 5-fold, indicating minimal precursor reutilization
during the course of our experiments. Turnover data indicate that increased
isotope incorporation into OMP in the epithelium is matched by an
accelerated rate of degradation in the bulb. This may be correlated with
the physiological state or developmental age of the primary neurons since
in young and Triton-treated adult mice, rapidly maturing "young" olfactory
neurons represent a larger proportion of the total population than in
adults. Thus, OMP behaves as a typical, relatively slowly transported
soluble protein (v = 2 to 4 mm/day, slow component b).