Macromolecular crowding accelerates amyloid formation by human apolipoprotein C-II

J Biol Chem. 2002 Mar 8;277(10):7824-30. doi: 10.1074/jbc.M110429200. Epub 2001 Dec 18.

Abstract

Human apolipoprotein C-II (apoC-II) slowly forms amyloid fibers in lipid-free solutions at physiological pH and salt concentrations (Hatters, D. M., MacPhee, C. E., Lawrence, L. J., Sawyer, W. H., and Howlett, G. J. (2000) Biochemistry 39, 8276--8283). Measurements of the time dependence of solution turbidity, thioflavin T reactivity, and the amount of sedimentable aggregate reveal that the rate and extent of amyloid formation are significantly increased by the addition of an inert polymer, dextran T10, at concentrations exceeding 20 g/liter. High dextran concentrations do not alter the secondary structure of the protein, fiber morphology, or the thioflavin T and Congo Red binding capacity of apoC-II amyloid. Analytical ultracentrifugation studies show that monomeric apoC-II does not associate significantly with dextran. The observed dependence of the overall rate of amyloid formation on dextran concentration may be accounted for quantitatively by a simple model for nonspecific volume exclusion. The model predicts that an increase in the fractional volume occupancy of macromolecules in a physiological fluid can nonspecifically accelerate the formation of amyloid fibers by any amyloidogenic protein.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyloid / biosynthesis*
  • Amyloid / chemistry*
  • Apolipoprotein C-II
  • Apolipoproteins C / chemistry*
  • Benzothiazoles
  • Circular Dichroism
  • Coloring Agents / pharmacology
  • Congo Red / pharmacology
  • Dextrans / chemistry
  • Dextrans / pharmacology
  • Dose-Response Relationship, Drug
  • Electric Conductivity
  • Fluorescent Dyes / pharmacology
  • Humans
  • Hydrogen-Ion Concentration
  • Kinetics
  • Lipids / chemistry
  • Microscopy, Electron
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Secondary
  • Recombinant Proteins / metabolism
  • Thermodynamics
  • Thiazoles / pharmacology
  • Time Factors
  • Ultracentrifugation

Substances

  • Amyloid
  • Apolipoprotein C-II
  • Apolipoproteins C
  • Benzothiazoles
  • Coloring Agents
  • Dextrans
  • Fluorescent Dyes
  • Lipids
  • Recombinant Proteins
  • Thiazoles
  • thioflavin T
  • Congo Red