title: Structure based aggregation studies reveal the presence of helix-rich intermediate during α-Synuclein aggregation.
abstract: Mechanistic understanding of nucleation dependent polymerization by α-synuclein (α-Syn) into toxic oligomers and amyloids is important for the drug development against Parkinson's disease. However the structural and morphological characterization during nucleation and subsequent fibrillation process of α-Syn is not clearly understood. Using a variety of complementary biophysical techniques monitoring entire pathway of nine different synucleins, we found that transition of unstructured conformation into β-sheet rich fibril formation involves helix-rich intermediates. These intermediates are common for all aggregating synucleins, contain high solvent-exposed hydrophobic surfaces, are cytotoxic to SHSY-5Y cells and accelerate α-Syn aggregation efficiently. A multidimensional NMR study characterizing the intermediate accompanied with site-specific fluorescence study suggests that the N-terminal and central portions mainly participate in the helix-rich intermediate formation while the C-terminus remained in an extended conformation. However, significant conformational transitions occur at the middle and at the C-terminus during helix to β-sheet transition as evident from Trp fluorescence study. Since partial helix-rich intermediates were also observed for other amyloidogenic proteins such as Aβ and IAPP, we hypothesize that this class of intermediates may be one of the important intermediates for amyloid formation pathway by many natively unstructured protein/peptides and represent a potential target for drug development against amyloid diseases.
authors.affiliation: Department of Biosciences and Bioengineering, IIT Bombay, Powai, Mumbai, India 400076.
authors.forename: Dhiman
authors.initials: D
authors.lastname: Ghosh
authors.affiliation: Department of Biosciences and Bioengineering, IIT Bombay, Powai, Mumbai, India 400076.
authors.forename: Pradeep K
authors.initials: PK
authors.lastname: Singh
authors.affiliation: Department of Biosciences and Bioengineering, IIT Bombay, Powai, Mumbai, India 400076.
authors.forename: Shruti
authors.initials: S
authors.lastname: Sahay
authors.affiliation: Department of Biosciences and Bioengineering, IIT Bombay, Powai, Mumbai, India 400076.
authors.forename: Narendra Nath
authors.initials: NN
authors.lastname: Jha
authors.affiliation: Department of Biosciences and Bioengineering, IIT Bombay, Powai, Mumbai, India 400076.
authors.forename: Reeba S
authors.initials: RS
authors.lastname: Jacob
authors.affiliation: Department of Biosciences and Bioengineering, IIT Bombay, Powai, Mumbai, India 400076.
authors.forename: Shamik
authors.initials: S
authors.lastname: Sen
authors.affiliation: Department of Biosciences and Bioengineering, IIT Bombay, Powai, Mumbai, India 400076.
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Kumar
authors.affiliation: Laboratory for Physical Chemistry, Wolfgang-Pauli-Str. 10, ETH Zurich, CH-8093 Zurich, Switzerland.
authors.forename: Roland
authors.initials: R
authors.lastname: Riek
authors.affiliation: Department of Biosciences and Bioengineering, IIT Bombay, Powai, Mumbai, India 400076.
authors.forename: Samir K
authors.initials: SK
authors.lastname: Maji
mesh_terms: D000682:Amyloid / Q000737:chemistry / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002942:Circular Dichroism; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D018625:Microscopy, Atomic Force; D008854:Microscopy, Electron; D019906:Nuclear Magnetic Resonance, Biomolecular; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000494:pharmacology; D017550:Spectroscopy, Fourier Transform Infrared; D051844:alpha-Synuclein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D000682:Amyloid; D011994:Recombinant Proteins; D051844:alpha-Synuclein