Role of a Mitochondrial Micropeptide in Regulating Innate Immune Responses
Authors
Bhatta, AnkitFaculty Advisor
Kate A FitzgeraldAcademic Program
Immunology and MicrobiologyUMass Chan Affiliations
Infectious Diseases and ImmunologyDocument Type
Doctoral DissertationPublication Date
2020-09-29Keywords
LncRNAlong noncoding RNA
noncoding RNA
Micropeptide
Short-ORF-encoded peptides
SEPs
inflammation
inflammasome
NLRP3
Nod-like receptor
bacterial LPS
mitochondria
innate immune signaling
influenza A virus
IAV
Immunology and Infectious Disease
Microbiology
Metadata
Show full item recordAbstract
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.DOI
10.13028/phqj-xc86Permanent Link to this Item
http://hdl.handle.net/20.500.14038/31335Rights
Copyright is held by the author, with all rights reserved.ae974a485f413a2113503eed53cd6c53
10.13028/phqj-xc86