Cloning of AL-1, a ligand for an Eph-related tyrosine kinase receptor involved in axon bundle formation

• Published in: Neuron (Cambridge, Mass.) Mass.), 1995, Vol.14 (5), p.973-981
• Main Authors: Winslow, John W, Moran, Paul, Valverde, Janet, Shih, Ai, Yuan, Jean O, Wong, Suzy C, Tsai, Siao Ping, Goddard, Audrey, Henzel, William J, Hefti, Franz, Beck, Klaus D, Caras, Ingrid W
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Axons - drug effects; Axons - physiology; Axons - ultrastructure; Base Sequence; Blotting, Northern; Brain - metabolism; Brain - ultrastructure; Cell Membrane - metabolism; Cells, Cultured; Cerebral Cortex - embryology; Cerebral Cortex - metabolism; Cerebral Cortex - ultrastructure; Cloning, Molecular; Ephrin-A2; Flow Cytometry; Fluorescent Antibody Technique; Hippocampus - metabolism; Hippocampus - ultrastructure; Immunoglobulin G; Ligands; Molecular Sequence Data; Rats; Rats, Wistar; Receptor Protein-Tyrosine Kinases - metabolism; Recombinant Fusion Proteins; Transcription Factors - chemistry; Transcription Factors - genetics; Transcription Factors - metabolism
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/0896-6273(95)90335-6

REK7 is an Eph-related tyrosine kinase receptor expressed exclusively in the nervous system, predominantly in hippocampus and cortex. A soluble REK7-IgG fusion protein, produced to analyze the biological role of REK7, prevents axon bundling in cocultures of cortical neurons with astrocytes, a model of late stage nervous system development and differentiation. Using REK7-IgG as an affinity reagent, we purified and cloned a novel REK7 ligand called AL-1, a GPI-linked protein homologous to other members of an emerging ligand family. Membrane attachment of AL-1 appears necessary for receptor activation, since REK7 on cortical neurons is efficiently activated by transfected cells expressing GPI-linked AL-1, but not by soluble AL-1. Consistent with this, soluble AL-1 blocks axon bundling. Our findings, together with the observation that both molecules are expressed in the brain, suggest a role in the formation of neuronal pathways, a crucial feature of nervous system development and regeneration.