title: A Novel Role of Numb as A Regulator of Pro-inflammatory Cytokine Production in Macrophages in Response to Toll-like Receptor 4.
abstract: Activation of macrophages triggers the release of pro-inflammatory cytokines leading to inflammation. Numb is a negative regulator of Notch signaling, but the role of Numb in macrophages is not fully understood. In this study, the role of Numb as a regulator of inflammatory responses in macrophages was investigated. Murine bone marrow-derived macrophages, in which expression of Numb was silenced, secreted significantly less TNFα, IL-6 and IL-12 and more IL-10 upon activation by lipopolysaccharide (LPS), a ligand for Toll-like receptor 4 (TLR4), despite increased Notch signaling. The Tnfα mRNA levels both in Numb-deficient and wild-type macrophages were not significantly different, unlike those of Il6 and Il12-p40. In Numb-deficient macrophages, the Tnfα mRNAs were degraded at faster rate, compared to those in control macrophages. Activation of p38 MAPK and NF-κΒ p65 were compromised in activated Numb deficient macrophages. Numb was found to interact with the E3 ubiquitin ligase, Itch, which reportedly regulates p38 MAPK. In addition, blocking the Notch signaling pathway in activated, Numb-deficient macrophages did not further reduce TNFα levels, suggesting a Notch-independent role for Numb. A proteomics approach revealed a novel function for Numb in regulating complex signaling cascades downstream of TLRs, partially involving Akt/NF-κB p65/p38 MAPK in macrophages.
authors.affiliation: 1] Interdisciplinary Program in Medical Microbiology, Graduate School, Chulalongkorn University, Bangkok 10330, Thailand [2] Center of Excellence in Immunology and Immune-mediated Diseases, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Patipark
authors.initials: P
authors.lastname: Kueanjinda
authors.affiliation: National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency, Pathum Thani, Thailand.
authors.forename: Sittiruk
authors.initials: S
authors.lastname: Roytrakul
authors.affiliation: 1] Center of Excellence in Immunology and Immune-mediated Diseases, Chulalongkorn University, Bangkok 10330, Thailand [2] Department of Microbiology, and Omics Sciences and Bioinformatics Center Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Tanapat
authors.initials: T
authors.lastname: Palaga
mesh_terms: D000818:Animals; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008264:Macrophages / Q000166:cytology / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D015846:Monokines / Q000096:biosynthesis* / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D015846:Monokines; D009419:Nerve Tissue Proteins; C106293:Numb protein, mouse; D051880:Receptors, Notch; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4