title: Role of glial cell line-derived neurotrophic factor (GDNF)-neural cell adhesion molecule (NCAM) interactions in induction of neurite outgrowth and identification of a binding site for NCAM in the heel region of GDNF.
abstract: The formation of appropriate neuronal circuits is an essential part of nervous system development and relies heavily on the outgrowth of axons and dendrites and their guidance to their respective targets. This process is governed by a large array of molecules, including glial cell line-derived neurotrophic factor (GDNF) and the neural cell adhesion molecule (NCAM), the interaction of which induce neurite outgrowth. In the present study the requirements for NCAM-mediated GDNF-induced neurite outgrowth were investigated in cultures of hippocampal neurons, which do not express Ret. We demonstrate that NCAM-mediated GDNF-induced signaling leading to neurite outgrowth is more complex than previously reported. It not only involves NCAM-140 and the Src family kinase Fyn but also uses NCAM-180 and the fibroblast growth factor receptor. We find that induction of neurite outgrowth by GDNF via NCAM or by trans-homophilic NCAM interactions are not mutually exclusive. However, whereas NCAM-induced neurite outgrowth primarily is mediated by NCAM-180, we demonstrate that GDNF-induced neurite outgrowth involves both NCAM-140 and NCAM-180. We also find that GDNF-induced neurite outgrowth via NCAM differs from NCAM-induced neurite outgrowth by being independent of NCAM polysialylation. Additionally, we investigated the structural basis for GDNF-NCAM interactions and find that NCAM Ig3 is necessary for GDNF binding. Furthermore, we identify within the heel region of GDNF a binding site for NCAM and demonstrate that a peptide encompassing this sequence mimics the effects of GDNF with regard to NCAM binding, activation of intracellular signaling, and induction of neurite outgrowth.
authors.affiliation: Protein Laboratory, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen N, DK-2200 Copenhagen, Denmark. jannen@sund.ku.dk
authors.forename: Janne
authors.initials: J
authors.lastname: Nielsen
authors.forename: Kamil
authors.initials: K
authors.lastname: Gotfryd
authors.forename: Shizhong
authors.initials: S
authors.lastname: Li
authors.forename: Nikolaj
authors.initials: N
authors.lastname: Kulahin
authors.forename: Vladislav
authors.initials: V
authors.lastname: Soroka
authors.forename: Kim K
authors.initials: KK
authors.lastname: Rasmussen
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Bock
authors.forename: Vladimir
authors.initials: V
authors.lastname: Berezin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000502:physiology; D002460:Cell Line; D002478:Cells, Cultured; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D019006:Neural Cell Adhesion Molecules / Q000502:physiology*; D016501:Neurites / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D051100:Glial Cell Line-Derived Neurotrophic Factor; D019006:Neural Cell Adhesion Molecules