Signal peptide‐regulated toxicity of a plant ribosome‐inactivating protein during cell stress

Marshall, Richard S.; D’Avila, Francesca; Cola, Alessandra Di; Traini, Roberta; Spanó, Laura; Fabbrini, Maria Serena; Ceriotti, Aldo

doi:10.1111/j.1365-313x.2010.04413.x

Cited by 21 publications

(32 citation statements)

References 71 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In mammalian cells, certain secretory proteins are considered to be degraded before reaching the ER membrane in the UPR (31). This substrate-specific translocational attenuation during ER stress was defined as a "pre-emptive quality control," and similar regulation was also suggested in plants (32). Thus, although a large segment of ER-localized mRNAs is considered to be degraded by IRE1 in the UPR in Arabidopsis, it may not necessarily be the case that all of the transcripts for SS/TM genes are RIDD targets.…”

Section: Discussionmentioning

confidence: 99%

Defects in IRE1 enhance cell death and fail to degrade mRNAs encoding secretory pathway proteins in the Arabidopsis unfolded protein response

Mishiba

Nagashima

Suzuki

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

169

167

View full text Add to dashboard Cite

The unfolded protein response (UPR) is a cellular response highly conserved in eukaryotes to obviate accumulation of misfolded proteins in the endoplasmic reticulum (ER). Inositol-requiring enzyme 1 (IRE1) catalyzes the cytoplasmic splicing of mRNA encoding bZIP transcription factors to activate the UPR signaling pathway. Arabidopsis IRE1 was recently shown to be involved in the cytoplasmic splicing of bZIP60 mRNA. In the present study, we demonstrated that an Arabidopsis mutant with defects in two IRE1 paralogs showed enhanced cell death upon ER stress compared with a mutant with defects in bZIP60 and wild type, suggesting an alternative function of IRE1 in the UPR. Analysis of our previous microarray data and subsequent quantitative PCR indicated degradation of mRNAs encoding secretory pathway proteins by tunicamycin, DTT, and heat in an IRE1-dependent manner. The degradation of mRNAs localized to the ER during the UPR was considered analogous to a molecular mechanism referred to as the regulated IRE1-dependent decay of mRNAs reported in metazoans. Another microarray analysis conducted in the condition repressing transcription with actinomycin D and a subsequent Gene Set Enrichment Analysis revealed the regulated IRE1-dependent decay of mRNAs-mediated degradation of a significant portion of mRNAs encoding the secretory pathway proteins. In the mutant with defects in IRE1, genes involved in the cytosolic protein response such as heat shock factor A2 were upregulated by tunicamycin, indicating the connection between the UPR and the cytosolic protein response.heat stress | protein folding | bioinformatics T he unfolded protein response (UPR) or the endoplasmic reticulum (ER) stress response is a cellular response that is highly conserved in eukaryotes to obviate accumulation of misfolded proteins and to alleviate protein overload in the ER (1-3). Inositol-requiring enzyme 1 (IRE1), which is the primary transducer of the UPR in various organisms, catalyzes the unconventional or cytoplasmic splicing of mRNAs encoding bZIP transcription factors to up-regulate the UPR-related genes, such as genes for the ER-resident molecular chaperones, through its ribonuclease domain. The cytoplasmic splicing by IRE1 activates the bZIP transcription factors HAC1, XBP1, and bZIP60 in yeast, animals, and plants, respectively, by producing active proteins. Although the fundamental mechanism of the cytoplasmic splicing by IRE1 appears to be highly conserved, the mechanism of transcription factor activation is diverse among organisms (4).In addition to the cytoplasmic splicing of mRNAs for transcription factors, other functions of metazoan IRE1 have been reported. One such function is the degradation of mRNAencoding proteins in the secretory pathway referred to as regulated IRE1-dependent decay (RIDD) (5-7). RIDD is considered to contribute to reducing the amount of proteins entering the ER in the UPR. The metazoan UPR has an alternative mechanism to reduce the amount of protein entering the ER, and this mechanism is regulated by PKR-li...

show abstract

Section: Discussionmentioning

confidence: 99%

Defects in IRE1 enhance cell death and fail to degrade mRNAs encoding secretory pathway proteins in the Arabidopsis unfolded protein response

Mishiba

Nagashima

Suzuki

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

169

167

View full text Add to dashboard Cite

show abstract

“…Specific signals may lead to a change in the subcellular localization of the toxin, or to the degradation of a putative RIP inhibitor [30]. One of these mechanisms might be embedded in the plant signal peptide, as we have recently demonstrated in the case of saporin [31] where cleavage of the signal peptide was found to represent an activation step in the saporin biosynthetic pathway. In vivo , mutations affecting signal peptide cleavage could clearly reduce (although not fully eliminate) host cell toxicity.…”

Section: Ribosome Inactivating Proteins and Plant Defense Mechanismentioning

confidence: 99%

Ribosome-Inactivating Proteins: From Plant Defense to Tumor Attack

Virgilio

Lombardi

Caliandro

et al. 2010

Toxins

Self Cite

146

128

View full text Add to dashboard Cite

Ribosome-inactivating proteins (RIPs) are EC3.2.32.22 N-glycosidases that recognize a universally conserved stem-loop structure in 23S/25S/28S rRNA, depurinating a single adenine (A4324 in rat) and irreversibly blocking protein translation, leading finally to cell death of intoxicated mammalian cells. Ricin, the plant RIP prototype that comprises a catalytic A subunit linked to a galactose-binding lectin B subunit to allow cell surface binding and toxin entry in most mammalian cells, shows a potency in the picomolar range. The most promising way to exploit plant RIPs as weapons against cancer cells is either by designing molecules in which the toxic domains are linked to selective tumor targeting domains or directly delivered as suicide genes for cancer gene therapy. Here, we will provide a comprehensive picture of plant RIPs and discuss successful designs and features of chimeric molecules having therapeutic potential.

show abstract

“…14 Mutation of these two residues in lysine 176 and glutamine 179 was shown to abolish toxicity by depleting protein synthesis inhibition in vitro 36,37 and in vivo (cytotoxicity abolishment in cultured cell lines). 17 Consistent with this, while the wild-type clone had shown to considerably reduce growth rate for E. coli BL21, 37 we were able to express the SAP-KQ and the ssSAP-KQ mutants in E. coli (Fig.…”

Section: Discussionmentioning

confidence: 99%