title: Solvent microenvironments and copper binding alters the conformation and toxicity of a prion fragment.
abstract: The secondary structures of amyloidogenic proteins are largely influenced by various intra and extra cellular microenvironments and metal ions that govern cytotoxicity. The secondary structure of a prion fragment, PrP(111-126), was determined using circular dichroism (CD) spectroscopy in various microenvironments. The conformational preferences of the prion peptide fragment were examined by changing solvent conditions and pH, and by introducing external stress (sonication). These physical and chemical environments simulate various cellular components at the water-membrane interface, namely differing aqueous environments and metal chelating ions. The results show that PrP(111-126) adopts different conformations in assembled and non-assembled forms. Aging studies on the PrP(111-126) peptide fragment in aqueous buffer demonstrated a structural transition from random coil to a stable β-sheet structure. A similar, but significantly accelerated structural transition was observed upon sonication in aqueous environment. With increasing TFE concentrations, the helical content of PrP(111-126) increased persistently during the structural transition process from random coil. In aqueous SDS solution, PrP(111-126) exhibited β-sheet conformation with greater α-helical content. No significant conformational changes were observed under various pH conditions. Addition of Cu(2+) ions inhibited the structural transition and fibril formation of the peptide in a cell free in vitro system. The fact that Cu(2+) supplementation attenuates the fibrillar assemblies and cytotoxicity of PrP(111-126) was witnessed through structural morphology studies using AFM as well as cytotoxicity using MTT measurements. We observed negligible effects during both physical and chemical stimulation on conformation of the prion fragment in the presence of Cu(2+) ions. The toxicity of PrP(111-126) to cultured astrocytes was reduced following the addition of Cu(2+) ions, owing to binding affinity of copper towards histidine moiety present in the peptide.
authors.affiliation: Biomaterials and Advanced Drug Delivery Laboratory, Stanford University School of Medicine, Stanford, California, United States of America.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Inayathullah
authors.affiliation: Bioorganic and Neurochemistry Laboratory, Central Leather Research Institute, Adyar, Chennai, India.
authors.forename: K S
authors.initials: KS
authors.lastname: Satheeshkumar
authors.affiliation: Biomaterials and Advanced Drug Delivery Laboratory, Stanford University School of Medicine, Stanford, California, United States of America.
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Malkovskiy
authors.affiliation: Department of Surgery, School of Medicine, Stanford University, Stanford, California, United States of America.
authors.forename: Antoine L
authors.initials: AL
authors.lastname: Carre
authors.affiliation: Biomaterials and Advanced Drug Delivery Laboratory, Stanford University School of Medicine, Stanford, California, United States of America.
authors.forename: Senthilkumar
authors.initials: S
authors.lastname: Sivanesan
authors.affiliation: Department of Chemical Engineering, Stanford University, Stanford, California, United States of America.
authors.forename: Jasper O
authors.initials: JO
authors.lastname: Hardesty
authors.affiliation: Biomaterials and Advanced Drug Delivery Laboratory, Stanford University School of Medicine, Stanford, California, United States of America ; Department of Neurology and Neurological Science, Stanford University School of Medicine, Stanford, California, United States of America ; Cardiovascular Pharmacology Division, Cardiovascular Institute, Stanford University School of Medicine, Stanford, California, United States of America.
authors.forename: Jayakumar
authors.initials: J
authors.lastname: Rajadas
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D003300:Copper / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D011328:Prions / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D051381:Rats; D017208:Rats, Wistar
chemical_list: D010455:Peptides; D011328:Prions; D003300:Copper