1
|
Monteith AJ, Vincent HA, Kang S, Li P, Claiborne TM, Rajfur Z, Jacobson K, Moorman NJ, Vilen BJ. mTORC2 Activity Disrupts Lysosome Acidification in Systemic Lupus Erythematosus by Impairing Caspase-1 Cleavage of Rab39a. THE JOURNAL OF IMMUNOLOGY 2018; 201:371-382. [PMID: 29866702 DOI: 10.4049/jimmunol.1701712] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 05/08/2018] [Indexed: 12/16/2022]
Abstract
Lysosomes maintain immune homeostasis through the degradation of phagocytosed apoptotic debris; however, the signaling events regulating lysosomal maturation remain undefined. In this study, we show that lysosome acidification, key to the maturation process, relies on mTOR complex 2 (mTORC2), activation of caspase-1, and cleavage of Rab39a. Mechanistically, the localization of cofilin to the phagosome recruits caspase-11, which results in the localized activation of caspase-1. Caspase-1 subsequently cleaves Rab39a on the phagosomal membrane, promoting lysosome acidification. Although caspase-1 is critical for lysosome acidification, its activation is independent of inflammasomes and cell death mediated by apoptosis-associated speck-like protein containing a caspase recruitment domain, revealing a role beyond pyroptosis. In lupus-prone murine macrophages, chronic mTORC2 activity decouples the signaling pathway, leaving Rab39a intact. As a result, the lysosome does not acidify, and degradation is impaired, thereby heightening the burden of immune complexes that activate FcγRI and sustain mTORC2 activity. This feedforward loop promotes chronic immune activation, leading to multiple lupus-associated pathologies. In summary, these findings identify the key molecules in a previously unappreciated signaling pathway that promote lysosome acidification. It also shows that this pathway is disrupted in systemic lupus erythematosus.
Collapse
Affiliation(s)
- Andrew J Monteith
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Heather A Vincent
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - SunAh Kang
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Patrick Li
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Tauris M Claiborne
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Zenon Rajfur
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599; and.,Department of Physics, Astronomy, and Applied Computer Science, Institute of Physics, Jagiellonian University, 31-007 Krakow, Poland
| | - Ken Jacobson
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599; and
| | - Nathaniel J Moorman
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Barbara J Vilen
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599;
| |
Collapse
|
2
|
Pollard KM, Kono DH. Requirements for innate immune pathways in environmentally induced autoimmunity. BMC Med 2013; 11:100. [PMID: 23557436 PMCID: PMC3616845 DOI: 10.1186/1741-7015-11-100] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Accepted: 03/07/2013] [Indexed: 02/06/2023] Open
Abstract
There is substantial evidence that environmental triggers in combination with genetic and stochastic factors play an important role in spontaneous autoimmune disease. Although the specific environmental agents and how they promote autoimmunity remain largely unknown, in part because of diverse etiologies, environmentally induced autoimmune models can provide insights into potential mechanisms. Studies of idiopathic and environmentally induced systemic autoimmunity show that they are mediated by common adaptive immune response genes. By contrast, although the innate immune system is indispensable for autoimmunity, there are clear differences in the molecular and cellular innate components that mediate specific systemic autoimmune diseases, suggesting distinct autoimmune-promoting pathways. Some of these differences may be related to the bifurcation of toll-like receptor signaling that distinguishes interferon regulatory factor 7-mediated type I interferon production from nuclear factor-κB-driven proinflammatory cytokine expression. Accordingly, idiopathic and pristane-induced systemic autoimmunity require both type I interferon and proinflammatory cytokines whereas the less aggressive mercury-induced autoimmunity, although dependent on nucleic acid-binding toll-like receptors, does not require type I interferon but needs proinflammatory cytokines. Scavenger receptors and the inflammasome may contribute to silica-induced autoimmunity. Greater understanding of the innate mechanisms responsible for idiopathic and environmentally induced autoimmunity should yield new information into the processes that instigate and drive systemic autoimmunity.
Collapse
Affiliation(s)
- Kenneth Michael Pollard
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
| | | |
Collapse
|