Talks
Presentation Type
Oral Presentation
Discipline Track
Biomedical Science
Abstract Type
Research/Clinical
Abstract
Background: Insulin resistance is associated with low circulating levels of lipopolysaccharide (LPS). Binding of LPS to Toll like receptor 4 (TLR4) leads to the internalization and trafficking of TLR4 resulting in activation of downstream signaling pathways. TLR4 internalization in macrophages leads to the activation of pro-inflammatory signaling pathways and production of factors linked to the development of insulin resistance. The extracellular signal-regulated kinase 1 and 2 (ERK1 and 2) are activated downstream of TLR4 and are associated with insulin resistance. We hypothesized that ERK1 and ERK2 regulate TLR4 internalization in macrophages when exposed to LPS.
Methods: We examined whether inhibition of ERK activity blocked LPS-mediated internalization of TLR4 in bone marrow derived macrophages (BMDM). To determine which ERK isoform is involved in regulating TLR4 internalization, we used siRNA to knockdown ERK1, ERK2, or both. BMDM were treated with LPS (100 ng/ml, 6hr). Loss of cell surface TLR4 expression was measured by flow cytometry as a readout for TLR4 internalization.
Results: LPS decreased TLR4 surface expression by 31.3%, but knockdown of ERK1, ERK2, or both prevented LPS-induced decrease of TLR4 surface expression (5.6%, no decrease, 0.9%, respectively). In addition, knockdown of either ERK1, ERK2, or both in RAW264.7 cells prevented LPS-induced activity of Rab5, the early endosomal protein associated with TLR4 translocation.
Conclusions: ERK regulates TLR4 endocytosis and trafficking in macrophages. We propose that ERK positively regulates LPS-mediated TLR4 internalization and inhibition of ERK signaling will protect against insulin resistance.
Academic/Professional Position
Faculty
Mentor/PI Department
Molecular Science
Recommended Citation
Reyna, Sara M. and Chang, Phoebe Fang-Mei, "ERK Required for Lipopolysaccharide-induced TLR4 Internalization in Macrophages" (2023). Research Symposium. 29.
https://scholarworks.utrgv.edu/somrs/2022/talks/29
ERK Required for Lipopolysaccharide-induced TLR4 Internalization in Macrophages
Background: Insulin resistance is associated with low circulating levels of lipopolysaccharide (LPS). Binding of LPS to Toll like receptor 4 (TLR4) leads to the internalization and trafficking of TLR4 resulting in activation of downstream signaling pathways. TLR4 internalization in macrophages leads to the activation of pro-inflammatory signaling pathways and production of factors linked to the development of insulin resistance. The extracellular signal-regulated kinase 1 and 2 (ERK1 and 2) are activated downstream of TLR4 and are associated with insulin resistance. We hypothesized that ERK1 and ERK2 regulate TLR4 internalization in macrophages when exposed to LPS.
Methods: We examined whether inhibition of ERK activity blocked LPS-mediated internalization of TLR4 in bone marrow derived macrophages (BMDM). To determine which ERK isoform is involved in regulating TLR4 internalization, we used siRNA to knockdown ERK1, ERK2, or both. BMDM were treated with LPS (100 ng/ml, 6hr). Loss of cell surface TLR4 expression was measured by flow cytometry as a readout for TLR4 internalization.
Results: LPS decreased TLR4 surface expression by 31.3%, but knockdown of ERK1, ERK2, or both prevented LPS-induced decrease of TLR4 surface expression (5.6%, no decrease, 0.9%, respectively). In addition, knockdown of either ERK1, ERK2, or both in RAW264.7 cells prevented LPS-induced activity of Rab5, the early endosomal protein associated with TLR4 translocation.
Conclusions: ERK regulates TLR4 endocytosis and trafficking in macrophages. We propose that ERK positively regulates LPS-mediated TLR4 internalization and inhibition of ERK signaling will protect against insulin resistance.