Brigitte Devaux

A GPI-linked protein that interacts with Ret to form a candidate neurturin receptor.

Glial-cell-line-derived neurotrophic factor (GDNF) and neurturin (NTN) are two structurally related, potent survival factors for sympathetic, sensory and central nervous system neurons. GDNF mediates its actions through a multicomponent receptor system composed of a ligand-binding glycosyl-phosphatidylinositol (GPI)-linked protein (designated GDNFR-α) and the transmembrane protein tyrosine kinase Ret. In contrast, the mechanism by which the NTN signal is transmitted is not well understood. Here we describe the identification and tissue distribution of a GPI-linked protein (designated NTNR-α) that is structurally related to GDNFR-α. We further demonstrate that NTNR-α binds NTN (Kd ∼ 10 pM) but not GDNF with high affinity; that GDNFR-α binds to GDNF but not NTN with high affinity; and that cellular responses to NTN require the presence of NTNR-α. Finally, we show that NTN, in the presence of NTNR-α, induces tyrosine-phosphorylation of Ret, and that NTN, NTNR-α and Ret form a physical complex on the cell surface. These findings identify Ret and NTNR-α as signalling and ligand-binding components, respectively, of a receptor for NTN and define a novel family of receptors for neurotrophic and differentiation factors composed of a shared transmembrane protein tyrosine kinase and a ligand-specific GPI-linked protein.

Mammalian-cell-produced neurturin (NTN) is more potent than purified Escherichia coli-produced NTN

Neurturin (NTN) is a recently identified homologue of glial-cell-line-derived neurotrophic factor. Both factors promote the survival of dopaminergic (DA) neurons. We investigated the biological activity of mammalian-cell-produced NTN versus purified Escherichia coli-produced NTN. Baby hamster kidney cells were engineered to stably secrete mature human NTN. Mammalian-cell-derived NTN enhanced the activity of embryonic DA neurons in vitro, with greater potency (maximum effect achieved in the picogram range) than purified E. coli-produced NTN. Cell-based delivery of NTN (less than 10 ng/day) was also shown to be biologically active in vivo. These results suggest that mammalian-cell-derived NTN, synthesized de novo and delivered in small quantities to the parenchyma at the target site, may be as active as much larger quantities of purified, E. coli-produced NTN, delivered by other means.

Broad specificity of GDNF family receptors GFRα1 and GFRα2 for GDNF and NTN in neurons and transfected cells

The glial cell line‐derived neurotrophic factor (GDNF) family of ligands binds to lipid anchored proteins termed GDNF family receptor (GFR)αs, and then activates the RET receptor tyrosine kinase, by ligand GFRα. The binding of soluble GFRαs to transfected cells suggested that different GFRαs were dedicated to particular ligands, with GDNF acting primarily or entirely through GFRα1, and neurturin (NTN), through GFRα2. More recent evidence has suggested the possibility of cross‐talk between these ligands and the two receptors. We examined here whether crosstalk between the GDNF ligands and the GFRαs is biologically relevant, using midbrain dopaminergic, and parasympathetic, submandibular gland neurons. By biochemical and genetic addition and/or deletion of GFRα1 and 2, we show that in both neuronal cell types, robust biological activities of GDNF or NTN can be mediated by either GFRα1 or GFRα2, although GDNF is slightly more potent in dopaminergic (DA) neurons which normally express GFRα1, and NTN in submandibular neurons which normally express GFRα2. Throughout the body, GDNF and NTN are likely to have important biological actions on both GFRα1‐ and GFRα2‐expressing cells. J. Neurosci. Res. 61:1–9, 2000.

Characterization of Novel Neutralizing Monoclonal Antibodies Specific to Human Neurturin

Neurturin (NTN) a structural and functional relative of glial cell line-derived neurotrophic factor, was originally identified based on its ability to support the survival of sympathetic neurons in culture. Similar to glial cell line-derived neurotrophic factor (GDNF), Neurturin has been shown to bind to a high affinity glycosylphosphatidylinositol (GPI)-linked receptor (GFRalpha2) and induce phosphorylation of the tyrosine kinase receptor Ret, resulting in the activation of the mitogen activated protein kinase (MAPK) signalling pathway. A panel of six novel murine monoclonal antibodies (MAbs) specific to human Neurturin has been developed and characterized. Four of the MAbs tested inhibit, to varying degrees, binding of NTN to the GPI-linked GFRalpha2 receptor. Three MAbs cross-react with the murine homolog. These antibodies have been shown to be useful reagents for Western blotting, immunohistochemistry, and also for the development of a sensitive, quantitative enzyme-linked immunosorbent assay (ELISA) for human NTN. Novel, specific MAbs with varying epitope specificities and blocking activity will be valuable tools for both the in vitro and in vivo characterization of NTN and its relationship to the GFRalpha2 and Ret receptors.

Correction: A GPI-linked protein that interacts with Retto form a candidate neurturin receptor

This corrects the article DOI: 10.1038/42722