title: Altered exon usage in the juxtamembrane domain of mouse and human RON regulates receptor activity and signaling specificity.
abstract: Alternative splicing of signaling proteins can contribute to the complexity of signaling networks. We find that expression of mouse RON, but not human RON, results in constitutive receptor autophosphorylation, ligand-independent activation of the mitogen-activated protein kinase pathway, and association of the receptor with c-Src. Using chimeric receptors, we mapped the region for this difference in signaling capacity of mouse and human RON to the juxtamembrane domain. Expression of these receptors in primary erythroid progenitor cells also demonstrated a functional difference in the ability of mouse and human RON to support erythropoietin-independent colony formation that mapped to the juxtamembrane domain. Splicing of the mouse RON receptor tyrosine kinase transcript results in the constitutive deletion of an exon used by all other known RON orthologs that encodes part of the juxtamembrane domain of the receptor. Mutational analysis indicated that the two tyrosines present in this region in human RON, one of which has been previously shown to be a c-Cbl binding site, are not responsible for this difference. However, deletion of this region in the context of human RON enhanced receptor phosphorylation, activation of mitogen-activated protein kinase, and association of c-Src at levels comparable with those observed with mouse RON. These data provide direct evidence that the divergence of exon usage among different species can generate a protein with novel activity and subsequently add to the complexity of cellular signaling regulation.
authors.affiliation: Department of Veterinary Science, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Wei
authors.forename: Li
authors.initials: L
authors.lastname: Hao
authors.forename: Shuang
authors.initials: S
authors.lastname: Ni
authors.forename: Qingping
authors.initials: Q
authors.lastname: Liu
authors.forename: Jie
authors.initials: J
authors.lastname: Xu
authors.forename: Pamela H
authors.initials: PH
authors.lastname: Correll
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D000081247:CSK Tyrosine-Protein Kinase; D002460:Cell Line; D002478:Cells, Cultured; D004252:DNA Mutational Analysis; D004789:Enzyme Activation; D004921:Erythropoietin / Q000737:chemistry; D005091:Exons; D017353:Gene Deletion; D006801:Humans; D008024:Ligands; D008156:Luciferases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016296:Mutagenesis; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D050721:Proto-Oncogene Proteins c-cbl / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000737:chemistry* / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction; D013045:Species Specificity; D013234:Stem Cells; D014162:Transfection; D014443:Tyrosine / Q000737:chemistry; D019061:src-Family Kinases
chemical_list: D008024:Ligands; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D004921:Erythropoietin; D014443:Tyrosine; D008156:Luciferases; D050721:Proto-Oncogene Proteins c-cbl; D011505:Protein-Tyrosine Kinases; C080835:RON protein; D020794:Receptor Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human