Structural highlights
Function
[BCAP_HUMAN] Signaling adapter that contributes to B-cell development by linking B-cell receptor (BCR) signaling to the phosphoinositide 3-kinase (PI3K)-Akt signaling pathway. Has a complementary role to the BCR coreceptor CD19, coupling BCR and PI3K activation by providing a docking site for the PI3K subunit PIK3R1. Alternatively, links Toll-like receptor (TLR) signaling to PI3K activation, a process preventing excessive inflammatory cytokine production. Also involved in the activation of PI3K in natural killer cells. May be involved in the survival of mature B-cells via activation of REL.[1]
Publication Abstract from PubMed
The B cell adaptor protein (BCAP) is a multimodular regulator of inflammatory signaling in diverse immune system cells. BCAP couples TLR signaling to phosphoinositide metabolism and inhibits MyD88-directed signal transduction. BCAP is recruited to the TLR signalosome forming multitypic interactions with the MAL and MyD88 signaling adaptors. In this study, we show that indirect dimerization of BCAP TIR is required for negative regulation of TLR signaling. This regulation is mediated by a transcription factor Ig (TIG/IPT) domain, a fold found in the NF-kappaB family of transcription factors. We have solved the crystal structure of the BCAP TIG and find that it is most similar to that of early B cell factor 1 (EBF1). In both cases, the dimer is stabilized by a helix-loop-helix motif at the C terminus and interactions between the beta-sheets of the Ig domains. BCAP is exclusively localized in the cytosol and is unable to bind DNA. Thus, the TIG domain is a promiscuous dimerization module that has been appropriated for a range of regulatory functions in gene expression and signal transduction.
Negative Regulation of TLR Signaling by BCAP Requires Dimerization of Its DBB Domain.,Lauenstein JU, Scherm MJ, Udgata A, Moncrieffe MC, Fisher DI, Gay NJ J Immunol. 2020 Mar 20. pii: jimmunol.1901210. doi: 10.4049/jimmunol.1901210. PMID:32198144[2]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Maruoka M, Suzuki J, Kawata S, Yoshida K, Hirao N, Sato S, Goff SP, Takeya T, Tani K, Shishido T. Identification of B cell adaptor for PI3-kinase (BCAP) as an Abl interactor 1-regulated substrate of Abl kinases. FEBS Lett. 2005 Jun 6;579(14):2986-90. PMID:15893754 doi:http://dx.doi.org/S0014-5793(05)00528-4
- ↑ Lauenstein JU, Scherm MJ, Udgata A, Moncrieffe MC, Fisher DI, Gay NJ. Negative Regulation of TLR Signaling by BCAP Requires Dimerization of Its DBB Domain. J Immunol. 2020 Mar 20. pii: jimmunol.1901210. doi: 10.4049/jimmunol.1901210. PMID:32198144 doi:http://dx.doi.org/10.4049/jimmunol.1901210
