Reelin Signals Through Apolipoprotein E Receptor 2 and Cdc42 to Increase Growth Cone Motility and Filopodia Formation
The Journal of Neuroscience, November 3, 2010 • 30(44):14759–14772 • 14759 Cellular/Molecular Reelin Signals through Apolipoprotein E Receptor 2 and Cdc42 to Increase Growth Cone Motility and Filopodia Formation Jost Leemhuis,1,2 Elisabeth Bouche´,1,3 Michael Frotscher,1,4 Frank Henle,1,2 Lutz Hein,2 Joachim Herz,1,6 Dieter K. Meyer,1,2 Marina Pichler,1,2 Gu¨nter Roth,5 Carsten Schwan,1,2 and Hans H. Bock1,3 1Center for Neuroscience, 2Institute of Experimental and Clinical Pharmacology and Toxicology, 3Department of Medicine II, 4Institute of Anatomy and Cell Biology, and 5Department of Microsystems Engineering, Albert-Ludwigs-University, 79104 Freiburg, Germany, and 6Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9046 Lipoprotein receptor signaling regulates the positioning and differentiation of postmitotic neurons during development and modulates neuronal plasticity in the mature brain. Depending on the contextual situation, the lipoprotein receptor ligand Reelin can have opposing effects on cortical neurons. We show that Reelin increases growth cone motility and filopodia formation, and identify the underlying signaling cascade. Reelin activates the Rho GTPase Cdc42, known for its role in neuronal morphogenesis and directed migration, in an apolipoprotein E receptor 2-, Disabled-1-, and phosphatidylinositol 3-kinase-dependent manner. We demonstrate that neuronal vesicle trafficking, a Cdc42-controlled process, is increased after Reelin treatment and further provide evidence that the peptidergic VIP/ PACAP38 system and Reelin can functionally interact to promote axonal branching. In conclusion, Reelin-induced activation of Cdc42 contributes to the regulation of the cytoskeleton of individual responsive neurons and converges with other signaling cascades to orchestrate Rho GTPase activity and promote neuronal development.
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