Splicing variations in the ligand-binding domain of ApoER2 results in functional differences in the binding properties to Reelin.
Reelin plays critical roles in brain formation by binding to apolipoprotein E receptor 2 (ApoER2) and very low-density lipoprotein receptor. Several isoforms and fragments of Reelin are generated by alternative splicing and proteolytic cleavage. In addition, two splice variants of ApoER2 have been recognized, namely, LA1237 and LA12378, that differ in the number of ligand-binding type A (LA) repeats. Here, we quantitatively investigated the affinity between various isoforms/fragments of Reelin and the ApoER2 splice variants. ApoER2-LA1237 bound rather strongly to the Reelin central fragment than to the fragment bearing Reelin repeat 8 (RR8). ApoER2-LA12378 bound comparably to all Reelin fragments without the C-terminal region. These findings suggest that LA8 of ApoER2 and RR8 interfere with the interaction between the Reelin central fragment and ApoER2. Using a monoclonal antibody that only recognizes ApoER2-LA12378, we found that this variant of ApoER2 was expressed in the cerebral cortical wall and in the internal granule cells of the cerebellum during development. Primary-cultured cortical neurons did not express ApoER2-LA12378, and the extent of signal activation by Reelin fragments was well correlated with their affinity for ApoER2-LA1237. Therefore, proteolytic cleavage of Reelin and alternative splicing of ApoER2 may be involved in the fine regulation of Reelin signaling.
Hibi
Terumasa
T
Department of Biomedical Science, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Aichi 467-8603, Japan.
Mizutani
Masato
M
Baba
Atsushi
A
Hattori
Mitsuharu
M
D017398:Alternative Splicing; D000818:Animals; D000831:Animals, Newborn; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001665:Binding Sites; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D004622:Embryo, Mammalian; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D026502:LDL-Receptor Related Proteins; D008024:Ligands; D051379:Mice; D008813:Mice, Inbred ICR; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons; D011485:Protein Binding / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics; D017434:Protein Structure, Tertiary; D018110:Receptors, Lipoprotein / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D000091042:Reelin Protein; D012697:Serine Endopeptidases / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection / Q000379:methods
D000911:Antibodies, Monoclonal; D015816:Cell Adhesion Molecules, Neuronal; C103773:Dab1 protein, mouse; D016326:Extracellular Matrix Proteins; D053496:Inositol 1,4,5-Trisphosphate Receptors; D026502:LDL-Receptor Related Proteins; D008024:Ligands; D008869:Microtubule-Associated Proteins; C079240:Mtap2 protein, mouse; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; D018110:Receptors, Lipoprotein; D000091042:Reelin Protein; C098773:low density lipoprotein receptor-related protein 8; D049452:Green Fluorescent Proteins; C000717127:RELN protein, human; C000717128:Reln protein, mouse; D012697:Serine Endopeptidases