Mammalian GFRα-4, a Divergent Member of the GFRα Family of Coreceptors for Glial Cell Line-derived Neurotrophic Factor Family Ligands, Is a Receptor for the Neurotrophic Factor Persephin

Abstract

Four members of the glial cell line-derived neurotrophic factor family have been identified (GDNF, neurturin, persephin, and enovin/artemin). They bind to a specific membrane-anchored GDNF family receptor as follows: GFR␣-1 for GDNF, GFR␣-2 for neurturin, GFR␣-3 for enovin/artemin, and (chicken) GFR␣-4 for persephin. Subsequent signaling occurs through activation of a common transmembrane tyrosine kinase, cRET. GFR␣-4, the coreceptor for persephin, was previously identified in chicken only. We describe the cloning and characterization of a mammalian persephin receptor GFR␣-4. The novel GFR␣ receptor is substantially different in sequence from all known GFR␣s, including chicken GFR␣-4, and lacks the first cysteine-rich domain present in all previously characterized GFR␣s. At least two different GFR␣-4 splice variants exist in rat tissues, differing at their respective COOH termini. GFR␣-4 mRNA is expressed at low levels in different brain areas in the adult as well as in some peripheral tissues including testis and heart. Recombinant rat GFR␣-4 variants were expressed in mammalian cells and shown to be at least partially secreted from the cells. Persephin binds specifically and with high affinity (K D ‫؍‬ 6 nM) to the rat GFR␣-4 receptor, but no cRET activation could be demonstrated. Although the newly characterized mammalian GFR␣-4 receptor is structurally divergent from previously characterized GFR␣ family members, we suggest that it is a mammalian orthologue of the chicken persephin receptor. This discovery will allow a more detailed investigation of the biological targets of persephin action and its potential involvement in diseases of the nervous system.

The Candidate Neuroprotective Agent Artemin Induces Autonomic Neural Dysplasia without Preventing Peripheral Nerve Dysfunction

“…et al, 1997;Sanicola et al, 1997), GFRα-3 (Jing et al, 1997;Naveilhan et al, 1998;Trupp et al, 1998), and GFRα-4 . In vitro and in vivo studies indicate that each GFRα exhibits high affinity binding and potent RET activation (i.e., is "specific") when paired with a single trophic factor (Jing et al, 1996;Treanor et al, 1996;Baloh et al, 1997;Klein et al, 1997;Leitner et al, 1999;Masure et al, 1999;Masure et al, 2000;Lindahl 275 TOXICOLOGIC PATHOLOGY et al, 2001). The preferred interactions are GDNF-GFRα-1, NTN-GFRα-2, ART-GFRα-3, and PSP-GFRα-4.…”

A model for GFRα4 function and a potential modifying role in multiple endocrine neoplasia 2

“…GFRa4, the RET co-receptor for the GFL persephin (PSPN), is highly expressed in thyroid C-cells and in MTC (Lindahl et al, 2000;Masure et al, 2000). These observations suggested that GFRa4 might play a role in development of MTC tumours in the context of MEN 2, and that mutations of this locus might also contribute to MEN 2 phenotypes.…”

“…All GFRa4 isoforms lack the first cysteine-rich domain found in these proteins. The WTa isoform is most similar to other GFRas, containing two cysteine-rich domains, spanning seven alpha helices, and the conserved GPI-linkage (Figure 3), and has been shown to bind both RET and its soluble ligand PSPN and to stimulate RET phosphorylation and survival of neuronal cell types (Enokido et al, 1998;Masure et al, 2000;Lindahl et al, 2001). Compared to WTa, WTb lacks helices 4 and 5 (Figure 3) and has an odd number of cysteine residues that would result in an unpaired residue, potentially available for novel interactions.…”

“…GFRA4 has six coding exons that undergo alternative splicing to generate three variants (a, b, and c) in mouse and human but only two (a, b) in rat (Lindahl et al, 2000(Lindahl et al, , 2001Masure et al, 2000). In humans, introns 2, or 2 and 3, may form part of the GFRA4 coding sequence and exons 3 and 4 can be read in multiple reading frames, while a cryptic splice acceptor site in intron 3 can result in inclusion of an 11 bp sequence (exon 4b) in some transcripts (Figure 1).…”

Glial Cell Line-Derived Neurotrophic Factor and Neurturin Inhibit Neurite Outgrowth and Activate RhoA through GFRα2b, an Alternatively Spliced Isoform of GFRα2

“…It has been estimated that Ͼ50% of human multi-exon genes are alternatively spliced (Modrek and Lee, 2002). Multiple alternatively spliced variants of GFR␣1 (Sanicola et al, 1997;Dey et al, 1998;Shefelbine et al, 1998), GFR␣2 Dolatshad et al, 2002), and GFR␣4 (Lindahl et al, 2000(Lindahl et al, , 2001Masure et al, 2000) have been reported. Similarly, alternative spliced isoforms of the coreceptors RET (Lorenzo et al, 1997;de Graaff et al, 2001;Lee et al, 2002) and NCAM (Povlsen et al, 2003;Buttner et al, 2004) have been reported.…”