Journal of Neuroscience, Vol 9, 806-814, Copyright © 1989 by Society for Neuroscience
Apical localization of the alpha subunit of GTP-binding protein Go in choroidal and ciliated ependymocytes [published erratum appears in J Neurosci 1989 Apr;9(4):following Table of Contents]
S Peraldi, B Nguyen Than Dao, P Brabet, V Homburger, B Rouot, M Toutant, C Bouille, I Assenmacher, J Bockaert and J Gabrion
Laboratoire de Neurobiologie Endocrinologique, UA 1197 CNRS, Universite de Montpellier II, France.
The presence of GTP-binding proteins (G proteins) has been studied in
murine adult choroid plexuses and cultured fetal choroidal or hypothalamic
ependymal cells by ADP-ribosylation catalyzed by Bordetella pertussis toxin
(PTX) and by immunodetection using affinity- purified polyclonal antibodies
against the alpha subunit of the Go protein (Go alpha), the major brain G
protein. ADP-ribosylation with 32P-NAD and PTX of choroid plexus revealed
an intense labeling at the 40 kDa level in addition to the known
PTX-substrates at 41 kDa (Gi alpha) and 39 kDa (Go alpha). This 40 kDa
substrate was also predominant in cultured ependymal cells. However, a
positive immunoreactivity with the anti-Go alpha antibodies was detected at
the level of the 39 kDa faster component, indicating the presence of Go
alpha in both choroid plexuses and cultured ependymal cells. In thin frozen
sections as well as in cultured cells, Go alpha was mainly immunolocalized
at the apical pole of choroidal ependymocytes and in the kinocilia of
ciliated ependymal cells. At the ultrastructural level, using gold
immunoprobes, the immunoreactivity of a Go alpha-like protein was detected
on the cytoplasmic face of the apical plasma membrane, coated pits and
vesicles, and in the apical cytoplasmic matrix. In ciliated ependymal
cells, the positive immunostaining displayed a dotted pattern at the
surface of demembranated axonema of apical kinocilia. These findings
strongly suggest that G proteins, especially Go, are involved in
transducing chemical signals that modulate traffic and exchanges between
cerebrospinal fluid and ependyma through the apical membrane of
ependymocytes.