title: Preferential activation by galanin 1-15 fragment of the GalR1 protomer of a GalR1-GalR2 heteroreceptor complex.
abstract: The three cloned galanin receptors show a higher affinity for galanin than for galanin N-terminal fragments. Galanin fragment (1-15) binding sites were discovered in the rat Central Nervous System, especially in dorsal hippocampus, indicating a relevant role of galanin fragments in central galanin communication. The hypothesis was introduced that these N-terminal galanin fragment preferring sites are formed through the formation of GalR1-GalR2 heteromers which may play a significant role in mediating galanin fragment (1-15) signaling. In HEK293T cells evidence for the existence of GalR1-GalR2 heteroreceptor complexes were obtained with proximity ligation and BRET(2) assays. PLA positive blobs representing GalR1-GalR2 heteroreceptor complexes were also observed in the raphe-hippocampal system. In CRE luciferase reporter gene assays, galanin (1-15) was more potent than galanin (1-29) in inhibiting the forskolin-induced increase of luciferase activity in GalR1-GalR2 transfected cells. The inhibition of CREB by 50nM of galanin (1-15) and of galanin (1-29) was fully counteracted by the non-selective galanin antagonist M35 and the selective GalR2 antagonist M871. These results suggested that the orthosteric agonist binding site of GalR1 protomer may have an increased affinity for the galanin (1-15) vs galanin (1-29) which can lead to its demonstrated increase in potency to inhibit CREB vs galanin (1-29). In contrast, in NFAT reporter gene assays galanin (1-29) shows a higher efficacy than galanin (1-15) in increasing Gq/11 mediated signaling over the GalR2 of these heteroreceptor complexes. This disbalance in the signaling of the GalR1-GalR2 heteroreceptor complexes induced by galanin (1-15) may contribute to depression-like actions since GalR1 agonists produce such effects.
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Retzius väg 8, 17177 Stockholm, Sweden.
authors.forename: Dasiel O
authors.initials: DO
authors.lastname: Borroto-Escuela
authors.affiliation: Universidad de Málaga, Andalucía Tech, Facultad de Medicina, Campus deTeatinos s/n, 29071 Málaga, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Narvaez
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Retzius väg 8, 17177 Stockholm, Sweden; Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
authors.forename: Michael
authors.initials: M
authors.lastname: Di Palma
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Retzius väg 8, 17177 Stockholm, Sweden.
authors.forename: Feliciano
authors.initials: F
authors.lastname: Calvo
authors.affiliation: Department of Earth, Life and Environmental Sciences, Section of Physiology, Campus Scientifico Enrico Mattei, Urbino, Italy.
authors.forename: David
authors.initials: D
authors.lastname: Rodriguez
authors.affiliation: Universidad de Málaga, Andalucía Tech, Facultad de Medicina, Campus deTeatinos s/n, 29071 Málaga, Spain.
authors.forename: Carmelo
authors.initials: C
authors.lastname: Millon
authors.affiliation: Department of Earth, Life and Environmental Sciences, Section of Physiology, Campus Scientifico Enrico Mattei, Urbino, Italy.
authors.forename: Jens
authors.initials: J
authors.lastname: Carlsson
authors.affiliation: Department of Biomedical Sciences, University of Modena, Italy.
authors.forename: Luigi F
authors.initials: LF
authors.lastname: Agnati
authors.affiliation: Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, Terrassa 08222, Spain.
authors.forename: Pere
authors.initials: P
authors.lastname: Garriga
authors.affiliation: Universidad de Málaga, Andalucía Tech, Facultad de Medicina, Campus deTeatinos s/n, 29071 Málaga, Spain.
authors.forename: Zaida
authors.initials: Z
authors.lastname: Díaz-Cabiale
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Retzius väg 8, 17177 Stockholm, Sweden. Electronic address: Kjell.Fuxe@ki.se.
authors.forename: Kjell
authors.initials: K
authors.lastname: Fuxe
mesh_terms: D000494:Allosteric Regulation; D000818:Animals; D001920:Bradykinin / Q000031:analogs & derivatives / Q000494:pharmacology; D001931:Brain Mapping; D050882:CREB-Binding Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D038983:Galactolipids / Q000494:pharmacology; D019004:Galanin / Q000378:metabolism / Q000494:pharmacology*; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D055503:Protein Multimerization; D051381:Rats; D044091:Receptor, Galanin, Type 1 / Q000819:agonists / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D044092:Receptor, Galanin, Type 2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D038983:Galactolipids; D010446:Peptide Fragments; D044091:Receptor, Galanin, Type 1; D044092:Receptor, Galanin, Type 2; C086813:galanin (1-15); C074069:galanin-(1-13)-bradykinin-(2-9)-amide; D049452:Green Fluorescent Proteins; D019004:Galanin; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; D001920:Bradykinin
keywords: Allosteric receptor–receptor interactions; GalR1–GalR2 heteromers; Galanin; Heteroreceptor complexes; In situ Proximity Ligation Assay; N-terminal galanin fragment