Signal transduction by a fungal NOD-like receptor based on propagation of a prion amyloid fold

PLoS Biol. 2015 Feb 11;13(2):e1002059. doi: 10.1371/journal.pbio.1002059. eCollection 2015 Feb.

Abstract

In the fungus Podospora anserina, the [Het-s] prion induces programmed cell death by activating the HET-S pore-forming protein. The HET-s β-solenoid prion fold serves as a template for converting the HET-S prion-forming domain into the same fold. This conversion, in turn, activates the HET-S pore-forming domain. The gene immediately adjacent to het-S encodes NWD2, a Nod-like receptor (NLR) with an N-terminal motif similar to the elementary repeat unit of the β-solenoid fold. NLRs are immune receptors controlling cell death and host defense processes in animals, plants and fungi. We have proposed that, analogously to [Het-s], NWD2 can activate the HET-S pore-forming protein by converting its prion-forming region into the β-solenoid fold. Here, we analyze the ability of NWD2 to induce formation of the β-solenoid prion fold. We show that artificial NWD2 variants induce formation of the [Het-s] prion, specifically in presence of their cognate ligands. The N-terminal motif is responsible for this prion induction, and mutations predicted to affect the β-solenoid fold abolish templating activity. In vitro, the N-terminal motif assembles into infectious prion amyloids that display a structure resembling the β-solenoid fold. In vivo, the assembled form of the NWD2 N-terminal region activates the HET-S pore-forming protein. This study documenting the role of the β-solenoid fold in fungal NLR function further highlights the general importance of amyloid and prion-like signaling in immunity-related cell fate pathways.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Amyloidogenic Proteins / chemistry*
  • Amyloidogenic Proteins / genetics
  • Amyloidogenic Proteins / metabolism
  • Fungal Proteins / chemistry*
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism
  • Gene Expression
  • Models, Molecular
  • Molecular Sequence Data
  • Podospora / genetics
  • Podospora / metabolism*
  • Prions / chemistry*
  • Prions / genetics
  • Prions / metabolism
  • Protein Binding
  • Protein Folding
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Receptors, Cell Surface / chemistry*
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / metabolism
  • Sequence Alignment
  • Signal Transduction

Substances

  • Amyloidogenic Proteins
  • Fungal Proteins
  • HET-S protein, Podospora anserina
  • Prions
  • Receptors, Cell Surface

Grant support

This work was funded by a grant by ANR (STANDPRION ANR-11-BSV8-0001 to SJS and 13-PDOC-0017-01 to BH), by the Idex Bordeaux (Université de Bordeaux, PEPS 2014 to AL and SJS) and by the Fondation pour la Recherche Médicale (FRM—AJE20140630090 to AL). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.