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Recruitment of Cbl-b to B cell antigen receptor couples antigen recognition to Toll-like receptor 9 activation in late endosomes
Journal article   Open access   Peer reviewed

Recruitment of Cbl-b to B cell antigen receptor couples antigen recognition to Toll-like receptor 9 activation in late endosomes

Margaret Veselits, Azusa Tanaka, Stanley Lipkowitz, Shannon O'Neill, Roger Sciammas, Alison Finnegan, Jian Zhang and Marcus R Clark
PloS one, Vol.9(3), pp.e89792-e89792
2014
DOI: 10.1371/journal.pone.0089792
PMCID: PMC3961229
PMID: 24651487
url
https://doi.org/10.1371/journal.pone.0089792View
Published (Version of record) Open Access

Abstract

Casitas B-lineage lymphoma-b (Cbl-b) is a ubiquitin ligase (E3) that modulates signaling by tagging molecules for degradation. It is a complex protein with multiple domains and binding partners that are not involved in ubiquitinating substrates. Herein, we demonstrate that Cbl-b, but not c-Cbl, is recruited to the clustered B cell antigen receptor (BCR) and that Cbl-b is required for entry of endocytosed BCRs into late endosomes. The E3 activity of Cbl-b is not necessary for BCR endocytic trafficking. Rather, the ubiquitin associated (UBA) domain is required. Furthermore, the Cbl-b UBA domain is sufficient to confer the receptor trafficking functions of Cbl-b on c-Cbl. Cbl-b is also required for entry of the Toll-like receptor 9 (TLR9) into late endosomes and for the in vitro activation of TLR9 by BCR-captured ligands. These data indicate that Cbl-b acts as a scaffolding molecule to coordinate the delivery of the BCR and TLR9 into subcellular compartments required for productively delivering BCR-captured ligands to TLR9.
Adaptor Proteins, Signal Transducing - chemistry Protein Structure, Tertiary Proto-Oncogene Proteins c-cbl - metabolism Humans Mice, Inbred C57BL Ubiquitin-Protein Ligases - metabolism Mutant Proteins - metabolism Receptors, Antigen, B-Cell - metabolism Endosomes - metabolism Proto-Oncogene Proteins c-cbl - chemistry Protein Transport Endocytosis Animals Spleen - enzymology Antigens - immunology Adaptor Proteins, Signal Transducing - metabolism Toll-Like Receptor 9 - metabolism

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