LPS-induced Pellino3 degradation is mediated by p62-dependent autophagy

  • Background: In macrophages Toll-like receptor 4 (TLR4) is activated in response to lipopolysaccharide (LPS) and induces proinflammatory cytokine expression. Therefore, mechanisms terminating proinflammatory gene expression are important. Autophagy plays a central role in controlling innate immune responses by lysosomal degradation of signaling proteins, thus contributing to the resolution of inflammation. Autophagic proteins like p62 directly interact with molecules involved in the TLR4-signaling pathway, but a correlation with the IRAK E3 ligase and scaffold protein Pellino3 remains obscure. Hence, we are interested in elucidating the function of Pellino3 to prove our hypothesis that it is a key regulator in the TLR4-signaling cascade. Methods: We used the cecal ligation and puncture (CLP) mouse model causing polymicrobial sepsis to analyze Pellino3 protein and mRNA expression. Furthermore, we induced endotoxemia in RAW264.7 mouse macrophages by LPS treatment to verify in vivo experiments. Lentiviral Pellino3 knockdown in RAW264.7 macrophages was used for cytokine measurements at mRNA level. To analyze potential Pellino3 binding partners in TLR4-signaling by mass spectrometry (MS), we overexpressed FLAG-tagged Pellino3 in RAW264.7 macrophages, treated cells for 3, 6 and 24 hours with LPS and immunoprecipitated Pellino3 via its FLAG-tag. To consider Pellino3 degradation as a result of p62-mediated autophagy, we transiently knocked down p62 by siRNA in RAW264.7 macrophages and also pharmacologically blocked LPS-induced autophagy by Bafilomycin A1. Results: We demonstrated Pellino3 protein degradation in primary CD11b+ splenocytes after 24 hours following CLP operation and confirmed this in RAW264.7 macrophages after 24-hour LPS stimulation. Knockdown of Pellino3 attenuates proinflammatory cytokines, for example IL-6 mRNA, after 6 hours of LPS. Furthermore, we found by MS and verifying immunoprecipitation experiments that p62 is a Pellino3 binding partner, thus targeting Pellino3 for degradation. In line, both p62 knockdown and Bafilomycin A1 treatment prevent Pellino3 degradation, supporting an autophagic mechanism. Conclusion: Our observations highlight a regulatory role of Pellino3 on TLR4 signaling. Thus, antagonism of Pellino3 in the hyperinflammatory phase of sepsis may counteract the cytokine storm. Furthermore, stabilization of Pellino3 by inhibition of autophagy in the hypoinflammatory phase of sepsis may improve immunity. In consideration of these two conflictive sepsis phases, modulation of Pellino3 may provide a new strategy for the development of a therapy approach in sepsis.

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Metadaten
Author:Annika Heeg, Laura Kuchler, Lisa Eifler, Tilo Knape, Hermann Heide, Bernhard BrüneORCiD, Andreas von KnethenORCiDGND
URN:urn:nbn:de:hebis:30:3-268855
DOI:https://doi.org/10.1186/cc11737
ISSN:1466-609X
ISSN:1364-8535
Parent Title (English):Critical care
Publisher:BioMed Central
Place of publication:London
Document Type:Article
Language:English
Date of Publication (online):2012/11/21
Date of first Publication:2012/11/14
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2012/11/21
Volume:16
Issue:(Suppl 3):P50
Page Number:2
First Page:26
Last Page:27
Note:
© 2012 various authors, licensee BioMed Central Ltd. All articles published in this supplement are distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
HeBIS-PPN:313416486
Institutes:Biochemie, Chemie und Pharmazie / Biochemie und Chemie
Medizin / Medizin
Wissenschaftliche Zentren und koordinierte Programme / Sonderforschungsbereiche / Forschungskollegs
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 57 Biowissenschaften; Biologie / 570 Biowissenschaften; Biologie
Sammlungen:Universitätspublikationen
Sammlung Biologie / Sondersammelgebiets-Volltexte
Licence (German):License LogoCreative Commons - Namensnennung 2.0