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Updated: Dec 25, 2025

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Published on: January 7, 2019
Negative Regulation of TLR Signaling by BCAP Requires Dimerization of Its DBB Domain
Johannes U Lauenstein1, Michael J Scherm1, Atul Udgata1
1Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom; and.
B cell adaptor protein (BCAP) negatively regulates Toll-like receptor (TLR) signaling through its TIG/IPT domain. This domain mediates indirect dimerization, crucial for inhibiting inflammatory pathways in immune cells.
Area of Science:
- Immunology
- Molecular Biology
- Cell Signaling
Background:
- B cell adaptor protein (BCAP) regulates inflammatory signaling by coupling TLRs to phosphoinositide metabolism.
- BCAP inhibits MyD88-directed signal transduction and interacts with MAL and MyD88 adaptors in the TLR signalosome.
Purpose of the Study:
- To investigate the mechanism of BCAP-mediated negative regulation of TLR signaling.
- To elucidate the structural and functional role of the BCAP TIG/IPT domain.
Main Methods:
- Crystal structure determination of the BCAP TIG/IPT domain.
- Analysis of structural similarities with other proteins, such as EBF1.
- Investigation of BCAP localization and DNA-binding capabilities.
Main Results:
- Indirect dimerization of BCAP TIR is essential for negative regulation of TLR signaling.
- The BCAP TIG/IPT domain, structurally similar to EBF1, mediates this dimerization via a helix-loop-helix motif and β-sheet interactions.
- BCAP is localized in the cytosol and does not bind DNA.
Conclusions:
- The BCAP TIG/IPT domain functions as a promiscuous dimerization module.
- This module is repurposed for regulating gene expression and signal transduction pathways, specifically inhibiting TLR signaling.
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