| Reelin, Disabled-1 (Dab1), Apolipoprotein E Receptor 2 (ApoER2), and Very Low Density Lipoprotein Receptor (VLDLR) participate in a signaling pathway required for layer formation during mammalian brain development. Binding of Reelin to ApoER2 and VLDLR induces a rapid increase in tyrosine phosphorylation of Dab1, an adaptor protein that associates with the cytoplasmic domain of the lipoprotein receptors. To characterize the Reelin signaling pathway and the mechanisms through which Reelin functions, full-length Reelin was purified and characterized. My work has shown that this partially pure source of Reelin is a useful reagent in in vivo and in vitro assays, and this reagent has allowed my laboratory and numerous others to study the function of Reelin more effectively. Here I compared the roles of ApoER2 and VLDLR in Reelin signaling using a combination of biochemical and anatomical techniques. My work differentiates between the multiple cleavage forms of Reelin that are observed in vivo, and my data suggest that the 280 kDa form of Reelin binds to lipoprotein receptors with greater affinity than the other forms of Reelin. My findings demonstrate that ApoER2 and VLDLR are essential for Reelin signaling and that no other receptor molecules can compensate for their role in mediating tyrosine phosphorylation of Dab1. In addition, I present evidence that Reelin binds to ApoER2 with greater apparent affinity than to VLDLR. Not only that, this work shows that ApoER2 is more important than VLDLR in mediating proper development of the cerebral cortex. |
