RESUMEN
Reelin is an extracellular protein that controls many aspects of pre- and postnatal brain development and function. The molecular mechanisms that mediate postnatal activities of Reelin are not well understood. Here, we first set out to express and purify the full length Reelin protein and a biologically active central fragment. Second, we investigated in detail the signal transduction mechanisms elicited by these purified Reelin proteins in cortical neurons. Unexpectedly, we discovered that the full-length Reelin moiety, but not the central fragment, is capable of activating Erk1/2 signaling, leading to increased p90RSK phosphorylation and the induction of immediate-early gene expression. Remarkably, Erk1/2 activation is not mediated by the canonical signal transduction pathway, involving ApoER2/VLDLR and Dab1, that mediates other functions of Reelin in early brain development. The activation of Erk1/2 signaling likely contributes to the modulation of neuronal maturation and synaptic plasticity by Reelin in the postnatal and adult brain.
Asunto(s)
Moléculas de Adhesión Celular Neuronal/metabolismo , Corteza Cerebral/metabolismo , Proteínas de la Matriz Extracelular/metabolismo , Sistema de Señalización de MAP Quinasas , Proteínas del Tejido Nervioso/metabolismo , Neuronas/metabolismo , Serina Endopeptidasas/metabolismo , Animales , Moléculas de Adhesión Celular Neuronal/química , Moléculas de Adhesión Celular Neuronal/genética , Corteza Cerebral/citología , Corteza Cerebral/crecimiento & desarrollo , Proteínas de la Matriz Extracelular/química , Proteínas de la Matriz Extracelular/genética , Expresión Génica , Genes Inmediatos-Precoces , Heterocigoto , Proteínas Relacionadas con Receptor de LDL/metabolismo , Ratones , Ratones Endogámicos ICR , Ratones Noqueados , Ratones Mutantes Neurológicos , Proteínas del Tejido Nervioso/química , Proteínas del Tejido Nervioso/deficiencia , Proteínas del Tejido Nervioso/genética , Fragmentos de Péptidos/química , Fragmentos de Péptidos/genética , Fragmentos de Péptidos/metabolismo , Fosforilación , Proteínas Proto-Oncogénicas c-akt/metabolismo , Receptores de LDL/metabolismo , Proteína Reelina , Proteínas Quinasas S6 Ribosómicas 90-kDa/metabolismo , Serina Endopeptidasas/química , Serina Endopeptidasas/genéticaRESUMEN
Semaphorins (SEMAs) and their Plexin (PLXN) receptors are central regulators of metazoan cellular communication. SEMA-PLXND1 signaling plays important roles in cardiovascular, nervous, and immune system development, and cancer biology. However, little is known about the molecular mechanisms that modulate SEMA-PLXND1 signaling. As PLXND1 associates with GIPC family endocytic adaptors, we evaluated the requirement for the molecular determinants of their association and PLXND1's vascular role. Zebrafish that endogenously express a Plxnd1 receptor with a predicted impairment in GIPC binding exhibit low penetrance angiogenesis deficits and antiangiogenic drug hypersensitivity. Moreover, gipc mutant fish show angiogenic impairments that are ameliorated by reducing Plxnd1 signaling. Finally, GIPC depletion potentiates SEMA-PLXND1 signaling in cultured endothelial cells. These findings expand the vascular roles of GIPCs beyond those of the Vascular Endothelial Growth Factor (VEGF)-dependent, proangiogenic GIPC1-Neuropilin 1 complex, recasting GIPCs as negative modulators of antiangiogenic PLXND1 signaling and suggest that PLXND1 trafficking shapes vascular development.