title: Endocytosis of the tachykinin neuropeptide, neurokinin B, in astrocytes and its role in cellular copper uptake.
abstract: The tachykinin neuropeptide, neurokinin B (NKB), belongs to a family of peptides having diverse roles in the brain. NKB, along with several other tachykinins, has been identified as a copper-binding peptide, however the physiological relevance of the binding is unclear. Previously, NKB was shown to limit the ability of copper to enter astrocytes and disrupt calcium homeostasis and it was thought that the peptide was sequestering the metal extracellularly. Here we use a fluorescein-labelled NKB peptide (F-NKB) to show that NKB is not retained extracellularly, but is endocytosed within 10-20min after addition to the cell media. The endocytosis is not inhibited when NKB is delivered as a copper-complex, [CuII(F-NKB)2]. Endocytosis of NKB can increase intracellular copper. Comparison to cells cultured in copper-free buffer indicated that apo-NKB can facilitate uptake of copper found in normal culture media. To achieve this NKB must compete with a variety of copper proteins, and we show that NKB can successfully compete with copper-binding peptides derived from the prion protein, itself associated with Cu(II) and Zn(II) metabolism. We suggest a mechanism of receptor mediated endocytosis to account for the observations.
authors.affiliation: The School of Science and Health, Western Sydney University, Locked Bag 1797, Penrith, 2759, NSW, Australia.
authors.forename: Reeha
authors.initials: R
authors.lastname: Shahzad
authors.affiliation: The School of Science and Health, Western Sydney University, Locked Bag 1797, Penrith, 2759, NSW, Australia.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Jones
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK.
authors.forename: John H
authors.initials: JH
authors.lastname: Viles
authors.affiliation: The School of Science and Health, Western Sydney University, Locked Bag 1797, Penrith, 2759, NSW, Australia. Electronic address: c.jones@westernsydney.edu.au.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Jones
mesh_terms: D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D001667:Binding, Competitive; D045744:Cell Line, Tumor; D003300:Copper / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology*; D019793:Fluorescein / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D015287:Neurokinin B / Q000187:drug effects / Q000378:metabolism*; D000072002:Prion Proteins / Q000378:metabolism; D011485:Protein Binding
chemical_list: D005456:Fluorescent Dyes; D000072002:Prion Proteins; D003300:Copper; D015287:Neurokinin B; D019793:Fluorescein
keywords: Copper; Endocytosis; Neurodegeneration; Neurokinin B; Neuropeptide; Tachykinin