Lipopolysaccharide promotes Drp1-dependent mitochondrial fission and associated inflammatory responses in macrophages

Ronan Kapetanovic; Syeda Farhana Afroz; Divya Ramnath; Grace Mep Lawrence; Takashi Okada; James Eb Curson; Jost de Bruin; David P Fairlie; Kate Schroder; Justin C St John; Antje Blumenthal; Matthew J Sweet

doi:10.1111/imcb.12363

Lipopolysaccharide promotes Drp1-dependent mitochondrial fission and associated inflammatory responses in macrophages

Immunol Cell Biol. 2020 Aug;98(7):528-539. doi: 10.1111/imcb.12363. Epub 2020 Jul 20.

Authors

Ronan Kapetanovic^{1

2}, Syeda Farhana Afroz^{1

2}, Divya Ramnath^{1

2}, Grace Mep Lawrence^{1

2}, Takashi Okada³, James Eb Curson^{1

2}, Jost de Bruin^{1

2}, David P Fairlie^{1

2}, Kate Schroder^{1

2}, Justin C St John³, Antje Blumenthal⁴, Matthew J Sweet^{1

2}

Affiliations

¹ Institute for Molecular Bioscience (IMB), IMB Centre for Inflammation and Disease Research, The University of Queensland, Brisbane, QLD, 4072, Australia.
² Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, 4072, Australia.
³ The Mitochondrial Genetics Group, Robinson Research Institute, School of Medicine, Adelaide Health and Medical Sciences Building, The University of Adelaide, Adelaide, SA, 5005, Australia.
⁴ The University of Queensland Diamantina Institute, The University of Queensland, Brisbane, QLD, 4102, Australia.

Abstract

Mitochondria have a multitude of functions, including energy generation and cell signaling. Recent evidence suggests that mitochondrial dynamics (i.e. the balance between mitochondrial fission and fusion) also regulate immune functions. Here, we reveal that lipopolysaccharide (LPS) stimulation increases mitochondrial numbers in mouse bone marrow-derived macrophages (BMMs) and human monocyte-derived macrophages. In BMMs, this response requires Toll-like receptor 4 (Tlr4) and the TLR adaptor protein myeloid differentiation primary response 88 (MyD88) but is independent of mitochondrial biogenesis. Consistent with this phenomenon being a consequence of mitochondrial fission, the dynamin-related protein 1 (Drp1) GTPase that promotes mitochondrial fission is enriched on mitochondria in LPS-activated macrophages and is required for the LPS-mediated increase in mitochondrial numbers in both BMMs and mouse embryonic fibroblasts. Pharmacological agents that skew toward mitochondrial fusion also abrogated this response. LPS triggered acute Drp1 phosphorylation at serine 635 (S635), followed by sustained Drp1 dephosphorylation at serine 656 (S656), in BMMs. LPS-induced S656 dephosphorylation was abrogated in MyD88-deficient BMMs, suggesting that this post-translational modification is particularly important for Tlr4-inducible fission. Pharmacological or genetic targeting of Tlr4-inducible fission had selective effects on inflammatory mediator production, with LPS-inducible mitochondrial fission promoting the expression and/or secretion of a subset of inflammatory mediators in BMMs and mouse embryonic fibroblasts. Thus, triggering of Tlr4 results in MyD88-dependent activation of Drp1, leading to inducible mitochondrial fission and subsequent inflammatory responses in macrophages.

Keywords: Dynamin-related protein 1; Toll-like receptor; lipopolysaccharide; macrophage; mitochondrial dynamics; mitochondrial fission.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Cells, Cultured
Dynamins / metabolism*
Fibroblasts
Humans
Lipopolysaccharides*
Macrophages / immunology*
Mice
Mitochondrial Dynamics*
Mitochondrial Proteins
Myeloid Differentiation Factor 88
Toll-Like Receptor 4

Substances

Lipopolysaccharides
Mitochondrial Proteins
Myd88 protein, mouse
Myeloid Differentiation Factor 88
Tlr4 protein, mouse
Toll-Like Receptor 4
Dnm1l protein, mouse
Dynamins