c-AMP-mediated changes in the intracellular distribution of the myelin-related protein CNPase in olfactory ensheathing glia (OEG)

C-AMP-MEDIATED CHANGES IN THE INTRACELLULAR DISTRIBUTION OF THE MYELIN-RELATED PROTEIN CNPase IN OLFACTORY ENSHEATHING GLIA (OEG)^*

ALESSANDRA SANTOS-SILVA AND LENY A. CAVALCANTE

Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, RJ, Brazil

The olfactory system exhibits perennial plasticity with uninterrupted renewal of primary afferents and growth-permissive properties of the ensheathing glia. Although OEG may myelinate non-olfactory axons, there is little information on the factors controlling the ability of OEG to express myelin-related markers. We analyzed the expression of the membrane-skeletal protein CNPase in explants of the olfactory bulb (OB) cultured under control or c-AMP stimulated conditions. Explants from OB of young adult rats were cultured onto laminin-coated coverslips in DMEM-F12/ fetal calf serum medium. Explants were treated with M dibutyril c-AMP (diBu-c-AMP) or M forskolin (Fk) or vehicles only for 4 hours. Then they were washed and fixed with 4% paraformaldehyde and reacted with anti-CNPase or anti-MBP and anti-S100 or anti-GFAP or anti-vimentin antibodies and with either Cy3- or FITC-labeled secondary antibodies. Within the core of explants fixed after 3 days in vitro, there were GFAP+ astrocytes and cells with morphology typical of oligodendrocytes showing strong CNPase staining and a fragmented distribution of MBP immunoreactivity. GFAP+ cells of both fibroblast-like and multipolar morphology appeared halfway from the explant rim to the periphery. Outside of the control explants, there were short, radiating neurites and S100+ bipolar or tripolar cells which showed no anti-MBP binding. However, some of these cells displayed weak and diffuse CNPase immunoreactivity. After diBu-c-AMP or Fk, the proportion of S100+/ CNPase++ bipolar cells decreased in a dose-dependent manner, replaced by velate cells, also S100+/CNPase++, but with distributions of these markers different from that of bipolar cells. S100 immunoreactivity could usually be found far more distally than CNPase, extending to flat membrane expansions that were not CNPase+. In addition, CNPase became redistributed, showing an "interrupted-lines'' pattern both near the cell nucleus and in veins within proximal regions. Very similar patterns were obtained for highly-biotinylated proteins that are reliable markers for mitochondria which, by their turn, may reflect the location of stable microtubules. Our results show that OEG express CNPase and that cAMP plays a role in the control of the expression of a myelinating phenotype. — ( June 27, 2000 ).

Publication Dates

• Publication in this collection
  05 Oct 2000
• Date of issue
  Sept 2000