Ephrin A5

Ephrin A5 is a protein that in humans is encoded by the EFNA5 gene.

EFNA5
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 2X11, 3MX0, 4BK5, 4BKA, 4L0P, 4M4R
Identifiers
Aliases	EFNA5, AF1, EFL5, EPLG7, GLC1M, LERK7, RAGS, ephrin A5
External IDs	OMIM: 601535; MGI: 107444; HomoloGene: 1482; GeneCards: EFNA5; OMA:EFNA5 - orthologs
Gene location (Human) Chr. Chromosome 5 (human) Band 5q21.3 Start 107,376,894 bp End 107,670,937 bp
Gene location (Mouse) Chr. Chromosome 17 (mouse) Band 17 E1.1|17 32.57 cM Start 62,911,179 bp End 63,188,312 bp
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in hair follicle Brodmann area 23 middle temporal gyrus primary visual cortex germinal epithelium synovial joint parietal pleura nipple endothelial cell pancreatic ductal cell Top expressed in superior cervical ganglion utricle external carotid artery ciliary body internal carotid artery iris arcuate nucleus hand epithelium of lens epithelium of stomach More reference expression data BioGPS More reference expression data
Gene ontology Molecular function neurotrophin TRKC receptor binding transmembrane receptor protein tyrosine kinase activator activity neurotrophin TRKA receptor binding ephrin receptor binding chemorepellent activity neurotrophin TRKB receptor binding protein binding Cellular component membrane plasma membrane anchored component of external side of plasma membrane caveola anchored component of membrane basement membrane adherens junction cell periphery GABA-ergic synapse Biological process positive regulation of synapse assembly apoptotic process cell differentiation regulation of insulin secretion involved in cellular response to glucose stimulus positive regulation of protein phosphorylation negative chemotaxis regulation of actin cytoskeleton organization regulation of GTPase activity ephrin receptor signaling pathway regulation of microtubule cytoskeleton organization positive regulation of collateral sprouting nervous system development multicellular organism development regulation of cell-cell adhesion positive regulation of peptidyl-tyrosine phosphorylation regulation of focal adhesion assembly regulation of cell morphogenesis collateral sprouting negative regulation of substrate adhesion-dependent cell spreading retinal ganglion cell axon guidance cellular response to follicle-stimulating hormone stimulus cellular response to forskolin activation of transmembrane receptor protein tyrosine kinase activity axon guidance synaptic membrane adhesion Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 1946 13640 Ensembl ENSG00000184349 ENSMUSG00000048915 UniProt P52803 O08543 RefSeq (mRNA) NM_001962 NM_010109 NM_207654 RefSeq (protein) NP_001953 NP_034239 NP_997537 Location (UCSC) Chr 5: 107.38 – 107.67 Mb Chr 17: 62.91 – 63.19 Mb PubMed search
Wikidata
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Ephrin A5 is a glycosylphosphatidylinositol (GPI)-anchored protein of the ephrin-A subclass of ephrin ligands that binds to the EphA subclass of Eph receptors. Ephrin A5 has also been shown to bind to the EphB2 receptor.

Reverse signaling in growth cone survival

"Reverse" signaling is one unique property of ephrin ligands that allows for the transmission of an intracellular signal in ephrin-expressing cells that is distinct from the signal transmitted in Eph receptor-expressing cells. Although the mechanism of "reverse" signaling by ephrin-As is not well understood, it is relatively surprising considering that ephrin-A ligands are attached to the cell membrane solely by a GPI linkage and unlike ephrin-Bs, lack a potential intracellular signaling domain. Nonetheless, certain ephrin-A ligands are known to initiate reverse signaling cascades like ephrin A5, which has been shown to stimulate the spreading of growth cones in cultures of mouse spinal motor neurons. Reverse signaling by ephrin A5 was demonstrated to be GPI-dependent as the elimination of all GPI linkages by the application of a phosphatidlyinositol-specific phospholipase C abolished the positive effects of ephrin A5 on growth cone spreading. Additionally, EphA receptors were shown to exert opposite effects on motor neuron growth cones by reducing growth cone size.

Formation of the retinotopic map

This finding that ephrin A5 promotes growth cone survival that is opposite of EphA signaling and mediated directly by ephrin A5 reverse signaling has important implications for axon guidance as it provides a mechanism by which migrating axons expressing EphAs would preferentially avoid ephrin A5 expressing cells and possibly migrate towards cells with lower expression of ephrin A5. This mechanism is in fact the same one that mediates the guidance of retinal ganglion cells to distinct regions in the superior colliculus during the formation of the retinotopic map. High ephrin A5 expression on cells in the posterior region of the SC bind to EphAs expressed in RGCs migrating from the temporal retina, inducing growth cone collapse and repelling these RGCs away from the posterior SC towards a region of low ephrin A5 expression in the anterior SC.

Further reading

• Flanagan JG, Vanderhaeghen P (1998). "The ephrins and Eph receptors in neural development". Annu. Rev. Neurosci. 21: 309–45. doi:10.1146/annurev.neuro.21.1.309. PMID 9530499. S2CID 1278600.
• Zhou R (1998). "The Eph family receptors and ligands". Pharmacol. Ther. 77 (3): 151–81. doi:10.1016/S0163-7258(97)00112-5. PMID 9576626.
• Holder N, Klein R (1999). "Eph receptors and ephrins: effectors of morphogenesis". Development. 126 (10): 2033–44. doi:10.1242/dev.126.10.2033. PMID 10207129.
• Wilkinson DG (2000). "Eph receptors and ephrins: regulators of guidance and assembly". Int. Rev. Cytol. International Review of Cytology. 196: 177–244. doi:10.1016/S0074-7696(00)96005-4. ISBN 978-0-12-364600-2. PMID 10730216.
• Xu Q, Mellitzer G, Wilkinson DG (2001). "Roles of Eph receptors and ephrins in segmental patterning". Philos. Trans. R. Soc. Lond. B Biol. Sci. 355 (1399): 993–1002. doi:10.1098/rstb.2000.0635. PMC 1692797. PMID 11128993.
• Wilkinson DG (2001). "Multiple roles of EPH receptors and ephrins in neural development". Nat. Rev. Neurosci. 2 (3): 155–64. doi:10.1038/35058515. PMID 11256076. S2CID 205014301.
• Winslow JW, Moran P, Valverde J, et al. (1995). "Cloning of AL-1, a ligand for an Eph-related tyrosine kinase receptor involved in axon bundle formation". Neuron. 14 (5): 973–81. doi:10.1016/0896-6273(95)90335-6. PMID 7748564. S2CID 18373575.
• Gale NW, Holland SJ, Valenzuela DM, et al. (1996). "Eph receptors and ligands comprise two major specificity subclasses and are reciprocally compartmentalized during embryogenesis". Neuron. 17 (1): 9–19. doi:10.1016/S0896-6273(00)80276-7. PMID 8755474. S2CID 1075856.
• Lackmann M, Mann RJ, Kravets L, et al. (1997). "Ligand for EPH-related kinase (LERK) 7 is the preferred high affinity ligand for the HEK receptor". J. Biol. Chem. 272 (26): 16521–30. doi:10.1074/jbc.272.26.16521. PMID 9195962.
• Ephnomenclaturecommittee (1997). "Unified nomenclature for Eph family receptors and their ligands, the ephrins. Eph Nomenclature Committee". Cell. 90 (3): 403–4. doi:10.1016/S0092-8674(00)80500-0. PMID 9267020. S2CID 26773768.
• Ciossek T, Monschau B, Kremoser C, et al. (1998). "Eph receptor-ligand interactions are necessary for guidance of retinal ganglion cell axons in vitro". Eur. J. Neurosci. 10 (5): 1574–80. doi:10.1046/j.1460-9568.1998.00180.x. PMID 9751130. S2CID 20470923.
• Janis LS, Cassidy RM, Kromer LF (1999). "Ephrin-A binding and EphA receptor expression delineate the matrix compartment of the striatum". J. Neurosci. 19 (12): 4962–71. doi:10.1523/JNEUROSCI.19-12-04962.1999. PMC 6782661. PMID 10366629.
• Gerlai R, Shinsky N, Shih A, et al. (1999). "Regulation of learning by EphA receptors: a protein targeting study". J. Neurosci. 19 (21): 9538–49. doi:10.1523/JNEUROSCI.19-21-09538.1999. PMC 6782889. PMID 10531456.
• Davy A, Gale NW, Murray EW, et al. (2000). "Compartmentalized signaling by GPI-anchored ephrin-A5 requires the Fyn tyrosine kinase to regulate cellular adhesion". Genes Dev. 13 (23): 3125–35. doi:10.1101/gad.13.23.3125. PMC 317175. PMID 10601038.

External links

• Overview of all the structural information available in the PDB for UniProt: P52803 (Human Ephrin-A5) at the PDBe-KB.
• Overview of all the structural information available in the PDB for UniProt: O08543 (Mouse Ephrin-A5) at the PDBe-KB.