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Hop/Sti1 - A Two-Faced Cochaperone Involved in Pattern Recognition Receptor Maturation and Viral Infection.

ABSTRACT: Perception of pathogens by host pattern recognition receptors (PRRs) or R proteins is a prerequisite to promote successful immune responses. The Hsp70/Hsp90 organizing protein Hop/Sti1, a multifunctional cochaperone, has been implicated in the maturation of a receptor-like kinase (RLK) necessary for chitin sensing. However, it remains unknown whether Hop/Sti1 is generally participating in PRR genesis. Using RNA-interference (RNAi), we silenced Hop/Sti1 expression in Nicotiana tabacum to gain further insight into the role of the cochaperone in plant defense responses. As expected, transgenic plants do not respond to chitin treatment anymore. In contrast to this, trafficking and functionality of the flagellin PRR FLS2 were unaltered, suggesting a selective involvement of Hop/Sti1 during PRR maturation. Furthermore, Hop/Sti1 was identified as a cellular determinant of Potato virus Y (PVY) symptom development in tobacco, since PVY was able to accumulate to near wild-type level without provoking the usual veinal necrosis phenotype. In addition, typical antiviral host defense responses were suppressed in the transgenic plants. These data suggest that perception of PVY is dependent on Hop/Sti1-mediated receptor maturation, while viral symptoms represent a failing attempt to restrict PVY spread. In addition, Hop/Sti1 colocalized with virus-induced membrane aggregates in wild-type plants. The retention of Hop/Sti1 in potential viral replication complexes suggests a role during viral translation/replication, explaining why RNAi-lines do not exhibit increased susceptibility to PVY. This study provides evidence for a dual role of Hop/Sti1 in PRR maturation and pathogen perception as well as in promoting viral proliferation.

SUBMITTER: Lamm CE

PROVIDER: S-EPMC5641557 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Hop/Sti1 - A Two-Faced Cochaperone Involved in Pattern Recognition Receptor Maturation and Viral Infection.

Lamm Christian E CE Kraner Max E ME Hofmann Jörg J Börnke Frederik F Mock Hans-Peter HP Sonnewald Uwe U

Frontiers in plant science 20171011

Perception of pathogens by host pattern recognition receptors (PRRs) or R proteins is a prerequisite to promote successful immune responses. The Hsp70/Hsp90 organizing protein Hop/Sti1, a multifunctional cochaperone, has been implicated in the maturation of a receptor-like kinase (RLK) necessary for chitin sensing. However, it remains unknown whether Hop/Sti1 is generally participating in PRR genesis. Using RNA-interference (RNAi), we silenced Hop/Sti1 expression in <i>Nicotiana tabacum</i> to g ...[more]

PMID: 29075278

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Project description:Recent genome-wide screens reveal that the host cells express an arsenal of proteins that inhibit replication of plus-stranded RNA viruses by functioning as cell-intrinsic restriction factors of viral infections. One group of cell-intrinsic restriction factors against tombusviruses contains tetratricopeptide repeat (TPR) domains that directly interact with the viral replication proteins. In this paper, we find that the TPR domain-containing Hop-like stress-inducible protein 1 (Sti1p) cochaperone selectively inhibits the mitochondrial membrane-based replication of Carnation Italian ringspot tombusvirus (CIRV). In contrast, Sti1/Hop does not inhibit the peroxisome membrane-based replication of the closely related Tomato bushy stunt virus (TBSV) or Cucumber necrosis virus (CNV) in a yeast model or in plants. Deletion of STI1 in yeast leads to up to a 4-fold increase in CIRV replication, and knockdown of the orthologous Hop cochaperone in plants results in a 3-fold increase in CIRV accumulation. Overexpression of Sti1p derivatives in yeast reveals that the inhibitory function depends on the TPR1 domain known to interact with heat shock protein 70 (Hsp70), but not on the TPR2 domain interacting with Hsp90. In vitro CIRV replication studies based on isolated mitochondrial preparations and purified recombinant proteins has confirmed that Sti1p, similar to the TPR-containing Cyp40-like Cpr7p cyclophilin and the Ttc4 oncogene-like Cns1 cochaperone, is a strong inhibitor of CIRV replication. Sti1p interacts and colocalizes with the CIRV replication proteins in yeast. Our findings indicate that the TPR-containing Hop/Sti1 cochaperone could act as a cell-intrinsic virus restriction factor of the mitochondrial CIRV, but not against the peroxisomal tombusviruses in yeast and plants.The host cells express various cell-intrinsic restriction factors that inhibit the replication of plus-stranded RNA viruses. In this paper, the authors find that the Hop-like stress-inducible protein 1 (Sti1p) cochaperone selectively inhibits the mitochondrial membrane-based replication of Carnation Italian ringspot tombusvirus (CIRV) in yeast. Deletion of STI1 in yeast or knockdown of the orthologous Hop cochaperone in plants leads to increased CIRV replication. In addition, overexpression of Sti1p derivatives in yeast reveals that the inhibitory function depends on the TPR1 domain known to interact with heat shock protein 70 (Hsp70), but not on the TPR2 domain interacting with Hsp90. In vitro CIRV replication studies based on isolated mitochondrial preparations and purified recombinant proteins have confirmed that Sti1p is a strong inhibitor of CIRV replication. The authors' findings reveal that the Hop/Sti1 cochaperone could act as a cell-intrinsic restriction factor against the mitochondrial CIRV, but not against the related peroxisomal tombusviruses.

Dataset Information

Hop/Sti1 - A Two-Faced Cochaperone Involved in Pattern Recognition Receptor Maturation and Viral Infection.

Publications

Hop/Sti1 - A Two-Faced Cochaperone Involved in Pattern Recognition Receptor Maturation and Viral Infection.

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