H. Dreyfus et al., GANGLIOSIDE AND NEUROTROPHIC GROWTH-FACTOR INTERACTIONS IN RETINAL NEURONAL AND GLIAL-CELLS, Indian Journal of Biochemistry & Biophysics, 34(1-2), 1997, pp. 90-96
Ganglioside (GG) and neurotrophic growth factor (GF) interactions in r
etinal neuronal and glial cells have been very little studied. Rat ret
inas were mechanically separated into outer (photoreceptor or PR) and
inner (other neurons, IR) halves by planar vibratome sectioning and re
tinal Muller glial (RMG) cells were isolated and cultured according to
previously published methods. The distribution on a percent molar bas
is of individual GG was different between the two halves: PR were domi
nated by GD3 (48% total GG) and contained only trace amounts (< 4%) of
complex species (GT1b, GQ); IR was more typical of mature brain tissu
e, exhibiting substantial amounts (similar to 25%) of more complex GG.
The GG profile of RMG cells was also simple, dominated by GM3 (60%) a
nd GD1a (20%). A single addition to the medium of 500 pM bFGF or EGF f
or 48 hr to cultured RMG cells led to significant increases in total G
G levels of 30-40%. Such treatments by both growth factors induced inc
reases in GM3, whereas longer exposure (96 hr) of confluent RMG to the
se factors additionally stimulated synthesis of more complex GG. Incub
ations of RMG with [H-3]-glucosamine showed that GG synthesis was 2-fo
ld stimulated by growth factors. We also tested the effect of GM3 on o
ne of. the bFGF receptor transduction pathways, namely PI-3 kinase act
ivation. To our knowledge these data constitute the first demonstratio
n of neurotrophic factor stimulation of GG levels in cells of CNS in v
itro. Such complex interactions may have particularly important conseq
uences for neural physiopathology.