Dithiothreitol causes toxicity in C. elegans by modulating the methionine-homocysteine cycle

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Abstract

The redox reagent dithiothreitol (DTT) causes stress in the endoplasmic reticulum (ER) by disrupting its oxidative protein folding environment, which results in the accumulation and misfolding of the newly synthesized proteins. DTT may potentially impact cellular physiology by ER-independent mechanisms; however, such mechanisms remain poorly characterized. Using the nematode model Caenorhabditis elegans, here we show that DTT toxicity is modulated by the bacterial diet. Specifically, the dietary component vitamin B12 alleviates DTT toxicity in a methionine synthase-dependent manner. Using a forward genetic screen, we discover that loss-of-function of R08E5.3, an S-adenosylmethionine (SAM)-dependent methyltransferase, confers DTT resistance. DTT upregulates R08E5.3 expression and modulates the activity of the methionine-homocysteine cycle. Employing genetic and biochemical studies, we establish that DTT toxicity is a result of the depletion of SAM. Finally, we show that a functional IRE-1/XBP-1 unfolded protein response pathway is required to counteract toxicity at high, but not low, DTT concentrations.

Data availability

The whole-genome sequence data for JSJ1-JSJ12 have been submitted to the public repository, the Sequence Read Archive, with BioProject ID PRJNA786771. All data generated or analyzed during this study are included in the manuscript and supporting files. Source Data files have been provided for Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, Figure 6, Figure 1-figure supplement 1, Figure 2-figure supplement 1, Figure 3-figure supplement 2, Figure 3-figure supplement 3, Figure 3-figure supplement 4, and Figure 6-figure supplement 1

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Gokul G

Indian Institute of Science Education and Research, Bhopal, Bhopal, India

Competing interests
The authors declare that no competing interests exist.
Jogender Singh

Indian Institute of Science Education and Research, Mohali, Mohali, India

For correspondence
jogender@iisermohali.ac.in

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-7947-0405

Funding

Indian Institute of Science Education and Research Bhopal (INST/BIO/2019091)

Jogender Singh

Indian Institute of Science Education and Research Mohali (Intramural funds)

Jogender Singh

Science and Engineering Research Board (Startup Research Grant,SRG/2020/000022)

Jogender Singh

Department of Biotechnology, Ministry of Science and Technology, India (Ramalingaswami Re-entry Fellowship,BT/RLF/Re-entry/50/2020)

Jogender Singh

Department of Science and Technology, Ministry of Science and Technology, India (INSPIRE-SHE Scholarship)

Gokul G

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

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This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.