TI  - Two-hybrid system as a model to study the interaction of beta-amyloid
      peptide monomers.
PG  - 2065-70
AB  - The kinetics of amyloid fibril formation by <prot>beta-amyloid peptide</prot> (<prot>Abeta</prot>)
      are typical of a nucleation-dependent polymerization mechanism. This type
      of mechanism suggests that the study of the interaction of   <prot>Abeta</prot>   with
      itself can provide some valuable insights into Alzheimer disease
      amyloidosis. Interaction of   <prot>Abeta</prot>   with itself was explored with the yeast
      two-hybrid system. Fusion proteins were created by linking the <prot>Abeta</prot>
      fragment to a <prot>LexA</prot> DNA-binding domain (bait) and also to a <prot>B42</prot>
      transactivation domain (prey). Protein-protein interactions were measured
      by expression of these fusion proteins in Saccharomyces cerevisiae
      harboring <prot>lacZ</prot> (<prot>beta-galactosidase</prot>) and <prot>LEU2</prot> (<prot>leucine utilization</prot>) genes
      under the control of LexA-dependent operators. This approach suggests that
      the   <prot>Abeta</prot>   molecule is capable of interacting with itself in vivo in the
      yeast cell nucleus. <prot>LexA</prot> protein fused to the Drosophila protein <prot>bicoid</prot>
      (<prot>LexA</prot>-<prot>bicoid</prot>) failed to interact with the <prot>B42</prot> fragment fused to <prot>Abeta</prot>,
      indicating that the observed  <prot>Abeta</prot> - <prot>Abeta</prot>  interaction was specific.
      Specificity was further shown by the finding that no significant
      interaction was observed in yeast expressing <prot>LexA</prot>-<prot>Abeta</prot> bait when the <prot>B42</prot>
      transactivation domain was fused to an <prot>Abeta</prot> fragment with Phe-Phe at
      residues 19 and 20 replaced by Thr-Thr (AbetaTT), a finding that is
      consistent with in vitro observations made by others. Moreover, when a
      peptide fragment bearing this substitution was mixed with native
      <prot>Abeta</prot>-(1-40), it inhibited formation of fibrils in vitro as examined by
      electron microscopy. The findings presented in this paper suggest that the
      two-hybrid system can be used to study the interaction of <prot>Abeta</prot> monomers
      and to define the peptide sequences that may be important in
      nucleation-dependent aggregation.
AD  - Neuroscience Therapeutic Domain, Hoechst Marion Roussel Inc., Somerville,
