title: Differential copper binding to alpha-synuclein and its disease-associated mutants affect the aggregation and amyloid formation.
abstract: Copper is an essential trace element required for the proper functioning of various enzymes present in the central nervous system. An imbalance in the copper homeostasis results in the pathology of various neurodegenerative disorders including Parkinson's Disease. Hence, residue specific interaction of Cu2+to α-Syn along with the familial mutants H50Q and G51D needs to be studied in detail.
  
  
  
  We investigated the residue specific mapping of Cu2+binding sites and binding strength using solution-state NMR and ITC respectively. The aggregation kinetics, secondary structural changes, and morphology of the formed fibrils in the presence and absence of Cu2+were studied using fluorescence, CD, and AFM respectively.
  
  
  
  Copper binding to α-Syn takes place at three different sites with a higher affinity for the region 48-53. While one of the sites got abolished in the case of H50Q, the mutant G51D showed a binding pattern similar to WT. The aggregation kinetics of these proteins in the presence of Cu2+showed an enhanced rate of fibril formation with a pronounced effect for G51D.
  
  
  
  Cu2+binding results in the destabilization of long-range tertiary interactions in α-Syn leading to the exposure of highly amyloidogenic NAC region which results in the increased rate of fibril formation. Although the residues 48-53 have a stronger affinity for Cu2+in case of WT and G51D, the binding is not responsible for enhancing the rate of fibril formation in case of H50Q.
  
  
  
  These findings will help in the better understanding of Cu2+catalyzed aggregation of synucleins.
authors.affiliation: Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors.forename: Priyatosh
authors.initials: P
authors.lastname: Ranjan
authors.affiliation: Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors.forename: Dhiman
authors.initials: D
authors.lastname: Ghosh
authors.affiliation: Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors.forename: Deepthi S
authors.initials: DS
authors.lastname: Yarramala
authors.affiliation: Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India; IITB-Monash Research Academy, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors.forename: Subhadeep
authors.initials: S
authors.lastname: Das
authors.affiliation: Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors.forename: Samir K
authors.initials: SK
authors.lastname: Maji
authors.affiliation: Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India. Electronic address: ashutoshk@iitb.ac.in.
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Kumar
mesh_terms: D000682:Amyloid / Q000378:metabolism*; D058227:Amyloidogenic Proteins / Q000378:metabolism*; D000686:Amyloidosis / Q000378:metabolism / Q000473:pathology; D001665:Binding Sites; D002460:Cell Line; D003300:Copper / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D010300:Parkinson Disease / Q000378:metabolism / Q000473:pathology; D066263:Protein Aggregation, Pathological / Q000378:metabolism / Q000473:pathology; D051844:alpha-Synuclein / Q000378:metabolism*
chemical_list: D000682:Amyloid; D058227:Amyloidogenic Proteins; D051844:alpha-Synuclein; D003300:Copper
keywords: Copper; Long-range contacts; Non-amyloid-β component; α-Syn G51D; α-Syn H50Q