The proprotein convertase PC1/3 regulates TLR9 trafficking and the associated signaling pathways

• Published in: Scientific reports Vol. 6; no. 1; p. 19360
• Main Authors: Duhamel, M., Rodet, F., Murgoci, A. N., Desjardins, R., Gagnon, H., Wisztorski, M., Fournier, I., Day, R., Salzet, M.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 18.01.2016; Nature Publishing Group
• Subjects: 631/378/371; 631/80/86; Animals; Cytokines - biosynthesis; Endosomes; Endosomes - metabolism; Enzyme Activation - drug effects; Humanities and Social Sciences; Inflammation; Interleukin 1; Interleukin 6; Life Sciences; Localization; Macrophages; Macrophages, Alveolar - metabolism; Macrophages, Peritoneal - metabolism; Mice; Mice, Knockout; Mice, Transgenic; multidisciplinary; MyD88 protein; NF-kappa B - metabolism; NF-κB protein; Oligodeoxyribonucleotides - immunology; Oligodeoxyribonucleotides - pharmacology; Oligonucleotides; pH effects; Proprotein Convertase 1 - metabolism; Proprotein convertases; Protein Binding; Protein Transport; Proteolysis - drug effects; Rats; Rodents; Science; Signal Transduction; Stat3 protein; STAT3 Transcription Factor - metabolism; TLR4 protein; TLR9 protein; Toll-Like Receptor 9 - metabolism; Toll-like receptors; Tumor necrosis factor
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep19360

Endosomal TLR9 is considered as a potent anti-tumoral therapeutic target. Therefore, it is crucial to decipher the mechanisms controlling its trafficking since it determines TLR9 activation and signalling. At present, the scarcity of molecular information regarding the control of this trafficking and signalling is noticeable. We have recently demonstrated that in macrophages, proprotein convertase 1/3 (PC1/3) is a key regulator of TLR4 Myd88-dependent signalling. In the present study, we established that PC1/3 also regulates the endosomal TLR9. Under CpG-ODN challenge, we found that PC1/3 traffics rapidly to co-localize with TLR9 in CpG-ODN-containing endosomes with acidic pH. In PC1/3 knockdown macrophages, compartmentalization of TLR9 was altered and TLR9 clustered in multivesicular bodies (MVB) as demonstrated by co-localization with Rab7. This demonstrates that PC1/3 controls TLR9 trafficking. This clustering of TLR9 in MVB dampened the anti-inflammatory STAT3 signalling pathway while it promoted the pro-inflammatory NF-kB pathway. As a result, macrophages from PC1/3 KO mice and rat PC1/3-KD NR8383 macrophages secreted more pro-inflammatory cytokines such as TNF-α, IL6, IL1α and CXCL2. This is indicative of a M1 pro-inflammatory phenotype. Therefore, PC1/3 KD macrophages represent a relevant mean for cell therapy as “Trojan” macrophages.