title: Extracellular GAPDH binds to L1 and enhances neurite outgrowth.
abstract: We have identified glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a binding partner for the cell adhesion molecule L1. GAPDH binds to sites within the extracellular domain of L1, namely the immunoglobulin-like domains I-VI and the fibronectin type III homologous repeats 4-5. Extracellular GAPDH was detected at the cell surface of neuronal cells by surface biotinylation and immunocytochemistry. Addition of GAPDH antibodies to cultured cerebellar neurons inhibited L1-dependent neurite outgrowth in the presence of ATP, while the application of exogenous GAPDH promoted L1-dependent neurite outgrowth. Pre-treatment of substrate-coated L1-Fc with ATP and GAPDH, which phosphorylates L1, subsequently led to an enhanced neurite outgrowth. Furthermore, aggregation of L1-Fc carrying beads was enhanced in the presence of both GAPDH and ATP. L1-dependent neurite outgrowth and aggregation of L1 were diminished in the presence of alkaline phosphatase or a protein kinase inhibitor. Our results show that GAPDH-dependent phosphorylation of L1 is a novel mechanism in regulating L1-mediated neurite outgrowth.
authors.affiliation: Zentrum für Molekulare Neurobiologie, Universität Hamburg, Martinistrasse 52, 20246 Hamburg, Germany.
authors.forename: Tatjana
authors.initials: T
authors.lastname: Makhina
authors.forename: Gabriele
authors.initials: G
authors.lastname: Loers
authors.forename: Christian
authors.initials: C
authors.lastname: Schulze
authors.forename: Barbara
authors.initials: B
authors.lastname: Ueberle
authors.forename: Melitta
authors.initials: M
authors.lastname: Schachner
authors.forename: Ralf
authors.initials: R
authors.lastname: Kleene
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001932:Brain Neoplasms; D045744:Cell Line, Tumor; D002531:Cerebellum / Q000166:cytology; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D039842:Neural Cell Adhesion Molecule L1 / Q000235:genetics / Q000378:metabolism*; D019006:Neural Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism; D016501:Neurites / Q000502:physiology*; D009447:Neuroblastoma; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats
chemical_list: D007141:Immunoglobulin Fc Fragments; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules; D000255:Adenosine Triphosphate; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases