Abstract
Recent evidence suggests that signaling by the proinflammatory cytokine interleukin-1beta (IL-1beta) is dependent on reactive oxygen species derived from NADPH oxidase. Redox signaling in response to IL-1beta is known to require endocytosis of its cognate receptor (IL-1R1) following ligand binding and the formation of redox-active signaling endosomes that contain Nox2 (also called redoxosomes). The consequent generation of reactive oxygen species by redoxosomes is responsible for the downstream recruitment of IL-1R1 effectors (IRAK, TRAF6, and IkappaB kinase kinases) and ultimately for activation of the transcription factor NFkappaB. Despite this knowledge of the signaling events that occur downstream of redoxosome formation, an understanding of the mechanisms that coordinate the genesis of redoxosomes following IL-1beta stimulation has been lacking. Here, we demonstrate that lipid rafts play an important role in this process. We show that Nox2 and IL-1R1 localize to plasma membrane lipid rafts in the unstimulated state and that IL-1beta signals caveolin-1-dependent endocytosis of both proteins into the redoxosome. We also show that inhibiting lipid raft-mediated endocytosis prevents NFkappaB activation. Finally, we demonstrate that Vav1, a Rac1 guanine exchange factor and activator of Nox2, is recruited to lipid rafts following IL-1beta stimulation and that it is required for NFkappaB activation. Our results fill in an important mechanistic gap in the understanding of early IL-1R1 and Nox2 signaling events that control NFkappaB activation, a redox-dependent process important in inflammation.
Highlights
Allergies, trauma, and chemical exposure [1,2,3,4,5,6,7,8]
We show that, following IL-1 stimulation, effectors of the IL-1R1 pathway are recruited into lipid rafts and that Nox2 and IL-1R1 are co-endocytosed into lipid raft/EEA1positive early endosomes via a mechanism that requires caveolin-1
Because Nox2 was shown previously to be required for IL-1-dependent NFB activation in MCF-7 cells [14], we hypothesized that disrupting lipid rafts would interfere with NFB activation following IL-1 stimulation
Summary
Allergies, trauma, and chemical exposure [1,2,3,4,5,6,7,8]. A primary role for signaling by IL-1 in these inflammatory responses is the activation of NFB, a transcription factor that regulates a large number of immune molecules, apoptotic factors, anti-apoptotic factors, and other transcription factors [9]. Because Nox2 was shown previously to be required for IL-1-dependent NFB activation in MCF-7 cells [14], we hypothesized that disrupting lipid rafts would interfere with NFB activation following IL-1 stimulation. The ability of nystatin and filipin to inhibit IL-1-mediated NFB activation suggested that this signaling pathway is dependent on lipid rafts.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
