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Prion and nonprion amyloids: a comparison inspired by the yeast Sup35 protein

Vitaly V Kushnirov1, Aleksandra B Vishnevskaya, Ilya M Alexandrov

  • 1Institute of Experimental Cardiology, Cardiology Research Center, Moscow, Russia.

Prion
|January 24, 2009
PubMed

Insights

Yeast Sup35 protein forms amyloid polymers that can be either heritable prions or nonheritable amyloids. Polymer fragmentation frequency, influenced by chaperones like Hsp104, distinguishes these states and may explain prion infectivity.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Protein Aggregation

Background:

  • Prion determinants in yeast, like [PSI(+)], involve protein polymerization into amyloid fibers, exemplified by the Sup35 protein.
  • The Hsp104 chaperone's fragmentation of prion polymers is crucial for prion replication and influences phenotypic variation.
  • Sup35 can also form nonheritable, poorly fragmented amyloid polymers, distinct from prions.

Purpose of the Study:

  • To investigate the role of polymer fragmentation frequency in distinguishing yeast prion and nonprion amyloid states.
  • To explore the potential parallels between yeast amyloid formation and human amyloid diseases.
  • To propose a model for prion transmission barriers based on amyloid seeding mechanisms.

Main Methods:

  • Analysis of Sup35 protein polymerization and fragmentation dynamics in yeast.
  • Comparison of [PSI(+)] prion formation with nonheritable Sup35 amyloid formation.
  • Investigating the influence of Rnq1 prion polymers on Sup35 amyloid seeding and fragmentation.

Main Results:

  • Yeast Sup35 protein can model both heritable prion and nonheritable amyloid formations.
  • Polymer fragmentation frequency, mediated by Hsp104, is a key differentiator between prion and nonprion states.
  • Nonheritable Sup35 polymers are poorly fragmented and efficiently seeded by Rnq1 polymers.

Conclusions:

  • The frequency of amyloid polymer fragmentation is a critical factor distinguishing prion and nonprion amyloids in yeast.
  • This fragmentation mechanism may also be key in understanding mammalian prion and nonprion amyloid properties, including infectivity.
  • The "species barrier" in prion transmission could be explained by seeding of non-transmissible amyloids by heterologous prions.

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