Evidence for a ligand-specific signaling through GFRalpha-1, but not GFRalpha-2, in the absence of Ret.
Glial cell line-derived neurotrophic factor (GDNF) and neurturin (NTN) are two homologeous proteins that have been recognized as potent survival factors for distinct neuronal populations. GDNF and NTN act through a two-component receptor system consisting of the ligand-specific binding subunits GDNF family receptor (GFR)alpha-1 and GFRalpha-2 and the common transducing subunit c-Ret. In addition, it has been demonstrated that GDNF can signal through GFRalpha-1 in the absence of c-Ret. In the present study, we sought to determine whether a similar c-Ret-independent signaling applies for GFRalpha-2. In addition, we have characterized the ligand specificity of the c-Ret-independent action of GFRalphas. To establish an assay system for these studies, several neural cell lines were screened for the presence of GDNF and NTN receptor subunits by RT-PCR and immunoblot analysis. c-Ret expression was detectable only in Neuro2A cells, which did not express GFRalpha-1 or GFRalpha-2. The neuronal cell line LS expressed GFRalpha-2, and the glial cell line Mes42 expressed GFRalpha-1, whereas the neuronal cell line B104 expressed both GFRalpha-1 and GFRalpha-2. Stimulation of B104 and Mes42 cells with GDNF, but not with NTN, for 10 min resulted in CREB phosphorylation. In apparent contrast, neither NTN nor GDNF promoted CREB activation in LS and Neuro2A cells. Moreover, exposure of LS cells to NTN or GDNF also failed to activate AKT and ERK. Together these findings provide evidence that, in contrast to GFRalpha-1, GFRalpha-2 fails to signal in the absence of c-Ret. In addition, these observations reveal that c-Ret-independent signaling of GFRalpha-1 is ligand- specific and occurs only with GDNF.
Pezeshki
G
G
Anatomie und Zellbiologie, Universität Ulm, Ulm, Germany.
Franke
B
B
Engele
J
J
D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002490:Central Nervous System / Q000254:growth & development* / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000187:drug effects / Q000378:metabolism; D029721:Drosophila Proteins; D005333:Fetus; D051100:Glial Cell Line-Derived Neurotrophic Factor; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors; D015151:Immunoblotting; D008024:Ligands; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism; D009414:Nerve Growth Factors / Q000378:metabolism* / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000378:metabolism* / Q000494:pharmacology; D009457:Neuroglia / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D051101:Neurturin; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000172:deficiency* / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051096:Proto-Oncogene Proteins c-ret; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020794:Receptor Protein-Tyrosine Kinases / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
D017362:Cyclic AMP Response Element-Binding Protein; D029721:Drosophila Proteins; C495041:Gdnf protein, rat; C494989:Gfra1 protein, rat; C494992:Gfra2 protein, rat; D051100:Glial Cell Line-Derived Neurotrophic Factor; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors; D008024:Ligands; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D051101:Neurturin; C495057:Nrtn protein, rat; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases; C416649:Ret protein, Drosophila; C495001:Ret protein, rat; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases