Existence of muscarinic acetylcholine receptor (mAChR) and fibroblast growth factor receptor (FGFR) heteroreceptor complexes and their enhancement of neurite outgrowth in neural hippocampal cultures.
Recently, it was demonstrated that G-protein-coupled receptors (GPCRs) can transactivate tyrosine kinase receptors in absence of their ligands. In this work, driven by the observation that mAChRs and fibroblast growth factor receptors (FGFRs) share signalling pathways and regulation of brain functions, it was decided to explore whether mAChRs activation may transactivate FGFRs and, if so, to characterize the related trophic effects in cultured hippocampal neurons.



Oxotremorine-M transactivation of FGFRs and related trophic effects were tested in primary hippocampal neurons. Western blotting and in situ proximity ligation assay (PLA) were used to detect FGFR phosphorylation (pFGFR) levels and M1R-FGFR1 heteroreceptor complexes, respectively.



Oxotremorine-M, a non-selective mAChRs agonist, was able to transactivate FGFR and this transactivation was blocked by Src inhibitors. Oxotremorine-M treatment produced a significant increase in the primary neurite outgrowth that was blocked by pre-treatment with the pFGFR inhibitor SU5402 and Src inhibitors. This trophic effect was almost similar to that induced by fibroblast growth factor-2 (FGF-2). By using atropine as nonselective mAChRs or pirenzepine as selective antagonist for M1receptor (M1R) we could show that mAChRs are involved in modulating the pFGFRs. Using PLA, M1R-FGFR1 heteroreceptor complexes were identified in the hippocampus and cerebral cortex.



The current findings, by showing functional mAChR-FGFR interactions, will contribute to advance the understanding of the mechanisms involved in the actions of cholinergic drugs on neuronal plasticity.



Data may help to develop novel therapeutic strategies not only for neurodegenerative diseases but also for depression-induced atrophy of hippocampal neurons.
Department of Experimental Biomedicine and Clinical Neurosciences, University of Palermo, Corso Tukory 129, 90134 Palermo, Italy. Electronic address: valentina.diliberto@unipa.it.
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Di Liberto
Karolinska Instituet, Department of Neuroscience, Retzius väg 8, 17177 Stockholm, Sweden; Department of Biomolecular Science, Section of Physiology, University of Urbino, Campus Scientifico Enrico Mattei, via Ca' le Suore 2, I-61029 Urbino, Italy; Observatorio Cubano de Neurociencias, Grupo Bohío-Estudio, Zayas 50, 62100 Yaguajay, Cuba. Electronic address: Dasiel.Borroto.Escuela@ki.se.
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Borroto-Escuela
Department of Experimental Biomedicine and Clinical Neurosciences, University of Palermo, Corso Tukory 129, 90134 Palermo, Italy. Electronic address: monicafrinchi@hotmail.it.
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Frinchi
Department of Experimental Biomedicine and Clinical Neurosciences, University of Palermo, Corso Tukory 129, 90134 Palermo, Italy. Electronic address: vincenzoverdi.bio@libero.it.
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Verdi
Karolinska Instituet, Department of Neuroscience, Retzius väg 8, 17177 Stockholm, Sweden. Electronic address: Kjell.Fuxe@ki.se.
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Fuxe
Department of Experimental Biomedicine and Clinical Neurosciences, University of Palermo, Corso Tukory 129, 90134 Palermo, Italy. Electronic address: natale.belluardo@unipa.it.
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Belluardo
Department of Experimental Biomedicine and Clinical Neurosciences, University of Palermo, Corso Tukory 129, 90134 Palermo, Italy. Electronic address: giuseppa.mudo@unipa.it.
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Mudò
D000818:Animals; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D000071446:Neuronal Outgrowth / Q000502:physiology*; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010095:Oxotremorine / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000378:metabolism*; D043643:Receptor, Muscarinic M1 / Q000378:metabolism*; D017468:Receptors, Fibroblast Growth Factor / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D043643:Receptor, Muscarinic M1; D017468:Receptors, Fibroblast Growth Factor; D043562:Receptors, G-Protein-Coupled; D011976:Receptors, Muscarinic; D016222:Fibroblast Growth Factor 2; D010095:Oxotremorine; C042743:oxotremorine M; C496350:Fgfr1 protein, rat; D051496:Receptor, Fibroblast Growth Factor, Type 1
FGFR1; Heteroreceptor complexes; M(1) receptor; Neural plasticity; Transactivation