Return to search

Role of a Mitochondrial Micropeptide in Regulating Innate Immune Responses

Short ORF-encoded peptides (SEPs) are increasingly being identified as functional elements in various cellular processes. The current computational methods and experimental molecular biochemistry allow us to discover putative SEPs or micropeptides from proteogenomic datasets and experimentally validate them. Here, we identified a micropeptide produced from a putative long noncoding RNA (lncRNA) 1810058I24Rik which is downregulated in both human and murine myeloid cells exposed to lipopolysaccharide (LPS), as well as other TLR ligands and inflammatory cytokines. Analysis of lncRNA 1810058I24Rik subcellular localization revealed this transcript is localized in the cytosol, prompting us to evaluate its coding potential. In vitro translation with 35S-labeled methionine resulted in translation of a 47 amino acid micropeptide. Microscopy and subcellular fractionation studies in macrophages demonstrated endogenous expression of this peptide on the mitochondrion. We thus named this gene ‘Mitochondrial micropeptide-47 (Mm47)’. Functional studies using siRNA and Cripsr-cas9-mediated deletion in primary cells, showed that the transcriptional response downstream of TLR4 was not affected by Mm47 loss of function. In contrast, both the Crispr-cas9- and siRNA-targeted BMDM cells were compromised for Nlrp3 inflammasome responses. However, the primary macrophages derived from the Mm47 knockout mice do not require Mm47 for Nlrp3 activation, likely due to basal downregulation of a negative regulator microRNA of Nlrp3 called Mir-223. Notably, the Mm47-deficient mice are susceptible to influenza virus infection and succumb despite comparable antiviral and inflammatory response to wildtype mice. We hypothesize that the Mm47 deficiency may affect the antiviral resilience of mice due to secondary mitochondria dependent immunometabolic defect or failure of recovery from immune pathology, which warrants further investigation. This study therefore identifies a novel mitochondrial micropeptide Mm47 that is required for activation of the Nlrp3 inflammasome in cells and resistance to influenza virus infection. Broadly, this work highlights the presence of translatable ORFs is annotated noncoding RNA transcripts and underscores their importance in innate immunity and virus infection.

Identiferoai:union.ndltd.org:umassmed.edu/oai:escholarship.umassmed.edu:gsbs_diss-2117
Date29 September 2020
CreatorsBhatta, Ankit
PublishereScholarship@UMMS
Source SetsUniversity of Massachusetts Medical School
Detected LanguageEnglish
Typetext
Formatapplication/pdf
SourceGSBS Dissertations and Theses
RightsCopyright is held by the author, with all rights reserved., select

Page generated in 0.0025 seconds