In vivo aggregation of the HET-s prion protein of the fungus Podospora anserina.
We have proposed that the [Het-s] infectious cytoplasmic element of the filamentous fungus Podospora anserina is the prion form of the HET-s protein. The HET-s protein is involved in a cellular recognition phenomenon characteristic of filamentous fungi and known as heterokaryon incompatibility. Under the prion form, the HET-s protein causes a cell death reaction when co-expressed with the HET-S protein, from which it differs by only 13 amino acid residues. We show here that the HET-s protein can exist as two alternative states, a soluble and an aggregated form in vivo. As shown for the yeast prions, transition to the infectious prion form leads to aggregation of a HET-s--green fluorescent protein (GFP) fusion protein. The HET-s protein is aggregated in vivo when highly expressed. However, we could not demonstrate HET-s aggregation at wild-type expression levels, which could indicate that only a small fraction of the HET-s protein is in its aggregated form in vivo in wild-type [Het-s] strains. The antagonistic HET-S form is soluble even at high expression level. A double amino acid substitution in HET-s (D23A P33H), which abolishes prion infectivity, suppresses in vivo aggregation of the GFP fusion. Together, these results further support the model that the [Het-s] element corresponds to an abnormal self-perpetuating aggregated form of the HET-s protein.
Coustou-Linares
V
V
Laboratoire de Parasitologie Moléculaire, UMR 5016 CNRS/Université de Bordeaux 2, Bordeaux, France.
Maddelein
M L
ML
Bégueret
J
J
Saupe
S J
SJ
D002449:Cell Aggregation; D017931:DNA Primers; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics; D008856:Microscopy, Fluorescence; D016133:Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020037:Sordariales / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology; D014774:Virulence / Q000235:genetics
D017931:DNA Primers; D005656:Fungal Proteins; C083891:HET-S protein, Podospora anserina; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins