Abstract
Reelin operates through canonical and non-canonical pathways that mediate several aspects of brain development and function. Reelin's dimeric central fragment (CF), generated through proteolytic cleavage, is required for the lipoprotein-receptor-dependent canonical pathway activation. Here, we analyze the signaling properties of a variety of Reelin fragments and measure the differential binding affinities of monomeric and dimeric CF fragments to lipoprotein receptors to investigate the mode of canonical signal activation. We also present the cryoelectron tomography-solved dimeric structure of Reelin CF and support it using several other biophysical techniques. Our findings suggest that Reelin CF forms a covalent parallel dimer with some degree of flexibility between the two protein chains. As a result of this conformation, Reelin binds to lipoprotein receptors in a manner inaccessible to its monomeric form and is capable of stimulating canonical pathway signaling.
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•Cryo-ET reveals the architecture of a dimeric, signaling-competent Reelin fragment•Biophysical data confirm the structure and detail of Reelin's oligomerization state•A Reelin heterodimer initiates signal activation in dissociated neurons•Data support a canonical pathway activation model that relies on dimeric conformation
Several aspects of brain development and function are reliant on the secreted glycoprotein Reelin. Turk et al. characterize the binding and signaling properties of a variety of Reelin fragments. The authors also present the in-solution structure of Reelin's dimeric central fragment and propose a structure-informed model of signal activation.