Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) regulate the vesicle transport machinery in phagocytic cells. Within the secretory pathway, Sec22b is an endoplasmic reticulum–Golgi intermediate compartment (ERGIC)-resident SNARE that controls phagosome maturation and function in macrophages and dendritic cells. The secretory pathway controls the release of cytokines and may also impact the secretion of NO, which is synthesized by the Golgi-active inducible NO synthase (iNOS). Whether ERGIC SNARE Sec22b controls NO and cytokine secretion is unknown. Using murine bone marrow-derived dendritic cells, we demonstrated that inducible NO synthase colocalizes with ERGIC/Golgi markers, notably Sec22b and its partner syntaxin 5, in the cytoplasm and at the phagosome. Pharmacological blockade of the secretory pathway hindered NO and cytokine release, and inhibited NF-κB translocation to the nucleus. Importantly, RNA interference–mediated silencing of Sec22b revealed that NO and cytokine production were abrogated at the protein and mRNA levels. This correlated with reduced nuclear translocation of NF-κB. We also found that Sec22b co-occurs with NF-κB in both the cytoplasm and nucleus, pointing to a role for this SNARE in the shuttling of NF-κB. Collectively, our data unveiled a novel function for the ERGIC/Golgi, and its resident SNARE Sec22b, in the production and release of inflammatory mediators.

Soluble NSF attachment receptor (SNARE) proteins regulate the vesicle transport machinery in phagocytic cells. Within the secretory pathway, Sec22b is an ER-Golgi intermediate compartment (ERGIC)-resident SNARE that controls phagosome maturation and function in macrophages and dendritic cells. The ERGIC controls the release of cytokines and may impact that of nitric oxide (NO), the latter of which is synthesized by the Golgi-active inducible nitric oxide synthase (iNOS). Whether the ERGIC SNARE Sec22b controls NO and cytokine secretion, is unknown. Using bone marrow-derived dendritic cells (BMDC), we demonstrated that iNOS colocalizes with ERGIC/Golgi markers, notably Sec22b and its partner syntaxin-5 (Stx5), in the cytoplasm and at the phagosome. Pharmacological blockade of the secretory pathway hindered NO and cytokine release, and inhibited NFκB translocation to the nucleus. Importantly, RNAi-mediated silencing of Sec22b revealed that NO and cytokine production were abrogated at the protein and mRNA levels. This correlated with deregulated mitogen-activated protein kinase (MAPK) signalling and reduced nuclear translocation of NFκB. Collectively, our data unveiled a novel function for the ERGIC, and its resident SNARE Sec22b, in the release of inflammatory mediators.

Soluble NSF attachment receptor (SNARE) proteins regulate the vesicle transport machinery in phagocytic cells. Within the secretory pathway, Sec22b is an ER-Golgi intermediate compartment (ERGIC)-resident SNARE that controls phagosome maturation and function in macrophages and dendritic cells. The secretory pathway controls the release of cytokines and may also impact the secretion of nitric oxide (NO), which is synthesized by the Golgi-active inducible nitric oxide synthase (iNOS). Whether ERGIC SNARE Sec22b controls NO and cytokine secretion, is unknown. Using bone marrow-derived dendritic cells (BMDC), we demonstrated that iNOS colocalizes with ERGIC/Golgi markers, notably Sec22b and its partner syntaxin-5 (Stx5), in the cytoplasm and at the phagosome. Pharmacological blockade of the secretory pathway hindered NO and cytokine release, and inhibited NF-κB translocation to the nucleus. Importantly, RNAi-mediated silencing of Sec22b revealed that NO and cytokine production were abrogated at the protein and mRNA levels. This correlated with deregulated mitogen-activated protein kinase signalling and reduced nuclear translocation of NF-κB. We also found that Sec22b co-occurs with NF-κB in both the cytoplasm and nucleus, pointing to a role for this SNARE in the shuttling of NF-κB. Collectively, our data unveiled a novel function for the ER-Golgi, and its resident SNARE Sec22b, in the production and release of inflammatory mediators.