A Radioimmunoassay for Ependymins β and γ: Two Goldfish Brain Proteins Involved in Behavioral Plasticity

Abstract

A radioimmunoassay (RIA) using 125I-labeled antigen was developed for the quantitative determination of 2 goldfish brain proteins (ependymins .beta. and .gamma.). The proteins were isolated from the CSF and cells of the ependymal zone surrounding goldfish brain ventricles. The turnover rates of .beta. and .gamma. were previously specifically enhanced after the animals successfully acquired a new pattern of swimming behavior. Femtomole quantities of ependymin .beta. were measurable by the RIA. Ependymins .beta. and .gamma. had common immunological properties, since 125I-.beta.-antigen bound to antibody could be displaced by unlabeled ependymin .gamma. and ependymin .beta. but not by a variety of other proteins including several purified glycoproteins isolated from goldfish brain. The ependymins constitute 14% of the total protein content of the brain extracellular fluid and are present as a minor component of the serum proteins (0.3%). Ependymins .beta. and .gamma. have an immunological reactivity in these fractions that can be increased by a factor of 30 on heating. The antigenicity of the molecules is apparently highly masked and may require some unraveling of the quaternary structure of the proteins before maximal interaction with the antisera becomes possible.