Journal of Neuroscience, Vol 8, 3181-3189, Copyright © 1988 by Society for Neuroscience
Changes in cytoskeletal proteins in the rat facial nucleus following axotomy
W Tetzlaff, MA Bisby and GW Kreutzberg
Department of Medical Physiology, University of Calgary, Alberta, Canada.
Changes in L-35S-methionine incorporation into cytoskeletal proteins of the
facial nucleus of the rat were studied at various times after unilateral
crush or resection of the facial nerve by using 2- dimensional gel
electrophoresis and fluorography. We found an increase in labeling of actin
and tubulin and a decrease in the 68 kDa and 150 kDa neurofilament
polypeptides (200 kDa was not studied). The increase in actin and decrease
in neurofilament polypeptide labeling was already significant by 24 hr
after nerve resection. These changes were more pronounced after nerve
resection than after nerve crush on day 7; actin labeling increased to
270%, and tubulin to 205% of contralateral normal nuclei after resection,
whereas both proteins increased to only 165% after crush. Neurofilament
labeling decreased to 28% of the contralateral side after resection and to
50% after crush. Immunocytochemistry with a monoclonal antibody to the 150
kDa neurofilament component revealed decreased immunoreactivity in the
axotomized facial axons at the inner facial genu, 1 cm proximal to the
crush. In contrast, neurofilament immunoreactivity was not decreased in the
axotomized perikarya of the facial motoneurons. All changes returned to
normal 3 weeks after crush. When axonal regeneration was impeded by nerve
resection, incorporation into tubulin remained elevated and into
neurofilament proteins remained depressed. Actin returned to normal after
either nerve resection or crush. We conclude that the synthesis of tubulin
and neurofilament proteins following axotomy is regulated by successful
axonal regeneration and/or target contact. Actin synthesis seems to be
regulated independently of target- derived factors.
Previous Article | Next Article
