Characterization of Drosophila GDNF receptor-like and evidence for its evolutionarily conserved interaction with neural cell adhesion molecule (NCAM)/FasII

• Published in: PloS one Vol. 7; no. 12; p. e51997
• Main Authors: Kallijärvi, Jukka, Stratoulias, Vassilis, Virtanen, Kristel, Hietakangas, Ville, Heino, Tapio I, Saarma, Mart
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 20.12.2012; Public Library of Science (PLoS)
• Subjects: Adhesion; Alleles; Alternative Splicing; Amino Acid Sequence; Animals; Biological Evolution; Biology; Biotechnology; Bone morphogenetic proteins; Cell adhesion; Cell adhesion & migration; Cell adhesion molecules; Cell Adhesion Molecules, Neuronal - genetics; Cell Adhesion Molecules, Neuronal - metabolism; Cell Line; Cell Membrane - metabolism; Central Nervous System - metabolism; Chromosomes; Clonal deletion; Defects; Drosophila; Drosophila melanogaster; Drosophila melanogaster - genetics; Drosophila melanogaster - metabolism; Drosophila Proteins - chemistry; Drosophila Proteins - genetics; Drosophila Proteins - metabolism; Eggs; Embryos; Epistasis, Genetic; Evolution; Female; Females; Fertility; Fertility - genetics; Gene Expression Regulation, Developmental; Gene mutation; Gene Order; Genetics; Glial cell line-derived neurotrophic factor; Glycosylation; GPI-Linked Proteins - chemistry; GPI-Linked Proteins - genetics; GPI-Linked Proteins - metabolism; Growth factors; Homology; Hybridization analysis; Insects; Kinases; Ligands; Male; Males; Mammals; Membrane proteins; Molecular Sequence Data; Morphogenesis - genetics; Mutation; Neural cell adhesion molecule; Neurology; Neuronal-glial interactions; Neurons - metabolism; Oocytes - growth & development; Oocytes - metabolism; Oogenesis; Phosphorylation; Plasmids; Protein Binding; Protein Interaction Domains and Motifs; Protein Isoforms; Protein Transport; Protein-tyrosine kinase receptors; Proteins; Proteomics; Proto-Oncogene Proteins c-ret - genetics; Proto-Oncogene Proteins c-ret - metabolism; Ret protein; Rodents; Signaling; Structure-function relationships; Transcription, Genetic; Transforming growth factors; Tyrosine; Vertebrates; Viability
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0051997

Glial cell line-derived neurotrophic factor (GDNF) family ligands are secreted growth factors distantly related to the TGF-β superfamily. In mammals, they bind to the GDNF family receptor α (Gfrα) and signal through the Ret receptor tyrosine kinase. In order to gain insight into the evolution of the Ret-Gfr-Gdnf signaling system, we have cloned and characterized the first invertebrate Gfr-like cDNA (DmGfrl) from Drosophila melanogaster and generated a DmGfrl mutant allele. We found that DmGfrl encodes a large GPI-anchored membrane protein with four GFR-like domains. In line with the fact that insects lack GDNF ligands, DmGfrl mediated neither Drosophila Ret phosphorylation nor mammalian RET phosphorylation. In situ hybridization analysis revealed that DmGfrl is expressed in the central and peripheral nervous systems throughout Drosophila development, but, surprisingly, DmGfrl and DmRet expression patterns were largely non-overlapping. We generated a DmGfrl null allele by genomic FLP deletion and found that both DmGfrl null females and males are viable but display fertility defects. The female fertility defect manifested as dorsal appendage malformation, small size and reduced viability of eggs laid by mutant females. In male flies DmGfrl interacted genetically with the Drosophila Ncam (neural cell adhesion molecule) homolog FasII to regulate fertility. Our results suggest that Ret and Gfrl did not function as an in cis receptor-coreceptor pair before the emergence of GDNF family ligands, and that the Ncam-Gfr interaction predated the in cis Ret-Gfr interaction in evolution. The fertility defects that we describe in DmGfrl null flies suggest that GDNF receptor-like has an evolutionarily ancient role in regulating male fertility and a previously unrecognized role in regulating oogenesis. These results shed light on the evolutionary aspects of the structure, expression and function of Ret-Gfrα and Ncam-Gfrα signaling complexes.