title: Co-localisation, heterophilic interactions and regulated expression of IgLON family proteins in the chick nervous system.
abstract: The chick glycoprotein GP55 has been shown to inhibit the growth and adhesion of DRG and forebrain neurons. GP55 consists of several members of the IgLON family, a group of glycoproteins including LAMP, OBCAM, CEPU-1 (chick)/neurotrimin (rat) and neurotractin (chick)/kilon (rat) thought to play a role in the guidance of growing axons. IgLONs belong to the Ig superfamily and have three C2 domains and a glycosyl phosphatidylinositol anchor which tethers them to the neuronal plasma membrane. We have now completed the deduced amino acid sequence for two isoforms of chicken OBCAM and used recombinant LAMP, OBCAM and CEPU-1 to raise antisera specific to these three IgLONs. LAMP and CEPU-1 are co-expressed on DRG and sympathetic neurons, while both overlapping and distinct expression patterns for LAMP, OBCAM and CEPU-1 are observed in retina. Analysis of IgLON mRNA expression reveals that alternatively spliced forms of LAMP and CEPU-1 are developmentally regulated. In an attempt to understand how the IgLONs function, we have begun to characterise their molecular interactions. LAMP and CEPU-1 have already been shown to interact homophilically. We now confirm that OBCAM will bind homophilically and also that LAMP, OBCAM and CEPU-1 will interact heterophilically with each other. We propose that IgLON activity will depend on the complement of IgLONs expressed by each neuron.
authors.affiliation: Department of Human Anatomy and Cell Biology, The University of Liverpool, New Medical School, Ashton St., L69 3GE, Liverpool, UK.
authors.forename: A P
authors.initials: AP
authors.lastname: Lodge
authors.forename: M R
authors.initials: MR
authors.lastname: Howard
authors.forename: C J
authors.initials: CJ
authors.lastname: McNamee
authors.forename: D J
authors.initials: DJ
authors.lastname: Moss
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D030161:Avian Proteins; D001921:Brain / Q000502:physiology; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics*; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000235:genetics*; D015816:Cell Adhesion Molecules, Neuronal / Q000737:chemistry / Q000235:genetics*; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D002642:Chick Embryo; D002645:Chickens / Q000235:genetics; D058851:GPI-Linked Proteins; D005727:Ganglia, Spinal / Q000502:physiology; D007074:Immunoglobulin G / Q000235:genetics; D007136:Immunoglobulins / Q000235:genetics*; D008562:Membrane Glycoproteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics*; D009424:Nervous System Physiological Phenomena; D019006:Neural Cell Adhesion Molecules / Q000737:chemistry / Q000235:genetics; D009474:Neurons / Q000502:physiology*; D016366:Open Reading Frames; D020033:Protein Isoforms / Q000235:genetics; D051381:Rats; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013564:Sympathetic Nervous System / Q000502:physiology
chemical_list: D030161:Avian Proteins; D002352:Carrier Proteins; D015815:Cell Adhesion Molecules; D015816:Cell Adhesion Molecules, Neuronal; D058851:GPI-Linked Proteins; D007074:Immunoglobulin G; D007136:Immunoglobulins; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D019006:Neural Cell Adhesion Molecules; C489215:Opcml protein, rat; D020033:Protein Isoforms; C095362:limbic system-associated membrane protein; C102493:neural CEPU-1 protein, chicken; C092530:neurotrimin