Differential involvement of metabotropic and p75 neurotrophin receptors in effects of nerve growth factor and neurotrophin-3 on cultured Purkinje cell survival.
We have examined the role of the p75 neurotrophin receptor in survival-promoting effects of nerve growth factor (NGF) and neurotrophin-3 (NT-3) on cultured Purkinje cells. Previously, we showed that NGF promotes Purkinje cell survival in conjunction with (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD), an agonist of metabotropic excitatory amino acid receptors, whereas NT-3 by itself increases cell number. We now present evidence that p75 plays different roles in Purkinje cell responses to the two neurotrophins. A metabotropic receptor of the mGluR1 subtype may interact with p75 function, so as to regulate Purkinje cell responsiveness to neurotrophins. When cerebellar cultures were grown for 6 days in the presence of ACPD and a mutant form of NGF that does not bind to p75, no increase in Purkinje cell number was observed. Moreover, the survival-promoting effect of wild-type NGF and ACPD could be inhibited by a neutralizing antiserum to p75 or by a pyrazoloquinazolinone inhibitor of neurotrophin binding to p75. In contrast, the response to NT-3 was potentiated by anti-p75 treatment and by the quinazolinone. These data indicate the mediation of p75 in the trophic response to NGF-ACPD and a negative modulatory role of p75 in the action of NT-3. To probe the role of ACPD in the p75-dependent response to NGF, metabotropic receptor subtype-specific ligands were tested. The pattern of agonist specificity implicated the mGluR1 subtype, a receptor that is expressed at high levels by Purkinje cells and linked to activation of protein kinase C (PKC). Down-regulation or blockade of PKC abolished the response to NGF-ACPD. Consistent with the opposite roles of p75 in effects of the two neurotrophins, blockade of mGluR1 or PKC potentiated the survival response elicited by NT-3. In sum, our data suggest that afferent excitatory transmitters activate specific metabotropic receptors to elicit a p75-mediated action of NGF. NT-3 acts on Purkinje cells by a different mechanism that is not absolutely p75-dependent and that is reduced by neurotrophin access to p75 and metabotropic receptor activity.
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Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, USA.
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D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D003515:Cycloleucine / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D009414:Nerve Growth Factors / Q000494:pharmacology*; D018696:Neuroprotective Agents / Q000494:pharmacology; D020933:Neurotrophin 3; D011493:Protein Kinase C / Q000378:metabolism; D011689:Purkinje Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D051381:Rats; D017207:Rats, Sprague-Dawley; D020800:Receptor, Nerve Growth Factor; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000502:physiology*; D017475:Receptors, Nerve Growth Factor / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D004791:Enzyme Inhibitors; D009414:Nerve Growth Factors; D018696:Neuroprotective Agents; D020933:Neurotrophin 3; D020800:Receptor, Nerve Growth Factor; D018094:Receptors, Metabotropic Glutamate; D017475:Receptors, Nerve Growth Factor; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane; C023010:4-hydroxyphenylglycine; D011493:Protein Kinase C; D005998:Glycine