The Journal of Neuroscience, December 1, 1998, 18(23):9751-9765
Identification of a Signaling Pathway Activated Specifically in
the Somatodendritic Compartment by a Heparan Sulfate That Regulates
Dendrite Growth
Sophie
Calvet1,
Patrick
Doherty2, and
Alain
Prochiantz1
1 Centre National de la Recherche Scientifique,
Unité de Recherche Associée 1414, Ecole Normale
Supérieure, 75230 Paris Cedex 05, France, and
2 Department of Experimental Pathology, United Medical and
Dental Schools, Guy's Hospital, London SE1 9RT, United Kingdom
In two earlier reports we demonstrated that natural heparan
sulfate, but not dermatan or chondroitin sulfate glycosaminoglycans, stimulate axonal elongation and inhibit dendrite growth in
vitro (). The latter specific effect on
dendrite elongation was reproduced by chemically synthesized heparan
sulfates and by SR 80037A, a purified sulfated and hexanoylated heparin fragment (). Adding radioactive SR 80037A to purified neurons demonstrated the existence, at the neuronal surface, of heparan sulfate-specific and saturable binding sites, suggesting that SR 80037A activates specific signal transduction pathways. In the
present study, using rat or mouse neurons from the embryonic cortex, we
show that SR 80037A signaling involves one or several G-coupled
receptor or receptors, small GTPases
A and/or
C, and one or
several PKCs. We also demonstrate that the rapid soma rounding elicited
by SR 80037A does not require protein synthesis but that the long-term
effect on dendrite initiation requires protein synthesis in a short
period after the addition of the heparan sulfate. Finally, by preparing
membranes from the somatodendritic or axonal compartments we
demonstrate that the identified signaling pathway is activated by SR
80037A primarily in the somatodendritic compartment and is not
sensitive to the addition of a dermatan sulfate glycosaminoglycan that
does not induce the axonal phenotype by impairing dendrite initiation
and elongation.
Key words:
neurons in culture; neuronal polarity; glycosaminoglycans; signal transduction; dendrite growth inhibition; cell rounding; cell permeable peptides
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