title: Mutants of metal binding site M1 in APP E2 show metal specific differences in binding of heparin but not of sorLA.
abstract: The amyloid precursor protein (APP) and its neurotoxic cleavage product Aβ are key players in the development of Alzheimer's disease (AD) and appear to be essential for neuronal development and cell homeostasis. Proteolytic processing of APP and its physiological function depend on its interaction with heparin and are influenced by the binding of metal ions and sorLA. We created various mutations of metal binding site M1 residing within the extracellular E2 domain of APP. Using isothermal titration calorimetry and circular dichroism spectroscopy, we analyzed the binding of Cu(2+) and Zn(2+) to APP E2 and identified two mutations that are most suited for functional studies to dissect ion specific effects of metal binding. The H313A mutation abrogates only copper-based effects, whereas the H382A mutation weakens any metal binding at M1 of APP E2. Subsequently, we tested the effect of Cu(2+) and Zn(2+) on the binding of heparin and sorLA to APP E2 using a chromatographic technique and surface plasmon resonance. We show that Zn(2+) and to a larger degree also Cu(2+) enhance the binding of heparin to APP E2, consistent with an extracellular regulation of the function of APP by both metal ions. In contrast, neither ion seemed to affect the interaction between APP E2 and sorLA. This supports an intracellular interaction between the latter two partners that would not sense extracellular variations of metal ions upon synaptic activity.
authors.affiliation: †Leibniz Institute for Age Research, Fritz Lipmann Institute (FLI), Protein Crystallography Group, Beutenbergstrasse 11, 07745 Jena, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Dienemann
authors.affiliation: †Leibniz Institute for Age Research, Fritz Lipmann Institute (FLI), Protein Crystallography Group, Beutenbergstrasse 11, 07745 Jena, Germany.
authors.forename: Ina
authors.initials: I
authors.lastname: Coburger
authors.affiliation: ‡The Lundbeck Foundation Research Center MIND, Danish Research Institute of Translational Neuroscience (DANDRITE) Nordic-EMBL Partnership, Department of Biomedicine, Aarhus University, Ole Worms Allé 3, DK-8000 Aarhus C, Denmark.
authors.forename: Arnela
authors.initials: A
authors.lastname: Mehmedbasic
authors.affiliation: ‡The Lundbeck Foundation Research Center MIND, Danish Research Institute of Translational Neuroscience (DANDRITE) Nordic-EMBL Partnership, Department of Biomedicine, Aarhus University, Ole Worms Allé 3, DK-8000 Aarhus C, Denmark.
authors.forename: Olav M
authors.initials: OM
authors.lastname: Andersen
authors.affiliation: †Leibniz Institute for Age Research, Fritz Lipmann Institute (FLI), Protein Crystallography Group, Beutenbergstrasse 11, 07745 Jena, Germany.
authors.forename: Manuel E
authors.initials: ME
authors.lastname: Than
mesh_terms: D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism; D019943:Amino Acid Substitution; D016564:Amyloid beta-Protein Precursor / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D006493:Heparin / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D026502:LDL-Receptor Related Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D011485:Protein Binding; D020349:Surface Plasmon Resonance; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism
chemical_list: C545487:APP protein, human; D016564:Amyloid beta-Protein Precursor; D026502:LDL-Receptor Related Proteins; D026901:Membrane Transport Proteins; C102582:SORL1 protein, human; D003300:Copper; D006493:Heparin; D015032:Zinc