Hysteretic behavior of proprotein convertase 1/3 (PC1/3).
Ontology highlight
ABSTRACT:
SUBMITTER: Icimoto MY
PROVIDER: S-EPMC3174183 | biostudies-literature | 2011
REPOSITORIES: biostudies-literature
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Project description:The proprotein convertase 1/3 is expressed in the regulated secretory pathway of neural and endocrine cells. Its major function is in the post-translational processing and activation of precursor proteins. The PC1/3 knock-out (KO) mouse model has allowed us to elucidate its physiological functions in studies focused primarily on neuroendocrine tissues. However, PC1/3 is also expressed in cells of the immune system, mainly in macrophages. The present study explores the effects of innate immune challenge in the PC1/3 KO mouse. PC1/3 KO mice have an enlarged spleen with marked disorganization of the marginal zone and red pulp. Immunohistochemical studies using various markers demonstrate a depletion of dendritic cells in PC1/3 KO spleens. When challenged with lipopolysaccharide, PC1/3 KO mice are more susceptible to septic shock than wild-type controls or other PC KO mice, such as PC2 and PC7 null mice. Plasma levels of proinflammatory cytokines (IL-6, IL-1?, and TNF-?) were very significantly elevated in PC1/3 KO mice, consistent with a hypercytokinemia, i.e. indicative of a major systemic uncontrolled inflammatory response or cytokine storm. Peritoneal macrophages isolated from PC1/3 KO mice also demonstrate elevated cytokine secretion when treated with LPS. Electron micrographs show morphological features indicating a prolonged activation of these cells following LPS stimulation. We also present evidence that the proinflammatory T(h)1 pathway is dominant in the PC1/3 KO mouse model. We conclude that aside from its important role in neuroendocrine functions PC1/3 also has an important role in the regulation of the innate immune system, most likely through the regulation of cytokine secretion in macrophages.
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Project description:Macrophages provide the first line of host immune defense. Their activation triggers the secretion of pro-inflammatory cytokines and chemokines recruiting other immune cells. In cancer, macrophages present an M2 anti-inflammatory phenotype promoting tumor growth. In this way, strategies need to be develop to reactivate macrophages. Previously thought to be expressed only in cells with a neural/neuroendocrine phenotype, the proprotein convertase 1/3 has been shown to also be expressed in macrophages and regulated as a function of the Toll-like receptor immune response. Here, we investigated the intracellular impact of the down-regulation of the proprotein convertase 1/3 in NR8383 macrophages and confirmed the results on macrophages from PC1/3 deficient mice. A complete proteomic study of secretomes and intracellular proteins was undertaken and revealed that inhibition of proprotein convertase 1/3 orient macrophages toward an M1 activated phenotype. This phenotype is characterized by filopodial extensions, Toll-like receptor 4 MyD88-dependent signaling, calcium entry augmentation and the secretion of pro-inflammatory factors. In response to endotoxin/lipopolysaccharide, these intracellular modifications increased, and the secreted factors attracted naïve T helper lymphocytes to promote the cytotoxic response. Importantly, the application of these factors onto breast and ovarian cancer cells resulted in a decrease viability or resistance. Under inhibitory conditions using interleukin 10, PC1/3-knockdown macrophages continued to secrete inflammatory factors. These data indicate that targeted inhibition of proprotein convertase 1/3 could represent a novel type of immune therapy to reactivate intra-tumoral macrophages.
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Project description:High grade gliomas are the most common brain tumors in adult. These tumors are characterized by a high infiltration in microglial cells and macrophages. The immunosuppressive tumor environment is known to orient immune cells toward a pro-tumoral and anti-inflammatory phenotype. Therefore, the current challenge for cancer therapy is to find a way to reorient macrophages toward an antitumoral phenotype. Previously, we demonstrated that macrophages secreted antitumoral factors when they were invalidated for the proprotein converstase 1/3 (PC1/3) and treated with LPS. However, achieving an activation of macrophages via LPS/TLR4/Myd88-dependent pathway appears yet unfeasible in cancer patients. On the contrary, the antitumor drug Paclitaxel is also known to activate the TLR4 MyD88-dependent signaling pathway and mimics LPS action. Therefore, we evaluated if PC1/3 knock-down (KD) macrophages could be activated by Paclitaxel and efficient against glioma. We report here that such a treatment of PC1/3 KD macrophages drove to the overexpression of proteins mainly involved in cytoskeleton rearrangement. In support of this finding, we found that these cells exhibited a Ca2+ increase after Paclitaxel treatment. This is indicative of a possible depolymerization of microtubules and may therefore reflect an activation of inflammatory pathways in macrophages. In such a way, we found that PC1/3 KD macrophages displayed a repression of the anti-inflammatory pathway STAT3 and secreted more pro-inflammatory cytokines. Extracellular vesicles isolated from these PC1/3 KD cells inhibited glioma growth. Finally, the supernatant collected from the coculture between glioma cells and PC1/3 KD macrophages contained more antitumoral factors. These findings unravel the potential value of a new therapeutic strategy combining Paclitaxel and PC1/3 inhibition to switch macrophages toward an antitumoral immunophenotype.
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