RING finger, HC subclass, found in E3 ubiquitin-protein ligase Cbl-b and similar proteins
Cbl-b, also known as Casitas B-lineage lymphoma proto-oncogene b, RING finger protein 56 (RNF56), SH3-binding protein Cbl-b, or signal transduction protein Cbl-b, has been identified as a regulator of antigen-specific, T cell-intrinsic, peripheral immune tolerance, a state also known as clonal anergy. It may inhibit activation of the p85 subunit of phosphoinositide 3-kinase (PI3K), protein kinase C-theta (PKC-theta), and phospholipase C-gamma1 (PLC-gamma1) and negatively regulates T-cell receptor-induced transcription factor nuclear factor kappaB (NF-kappaB) activation. In addition, Cbl-b may target multiple signaling molecules involved in transforming growth factor (TGF)-beta-mediated transactivation pathways. Cbl-b contains a tyrosine-kinase-binding domain (TKB, also known as the phosphotyrosine binding PTB domain, is composed of a four helix-bundle, a Ca2+ binding EF-hand and a highly variant SH2 domain), a proline rich domain, a nuclear localization signal, a C3HC4-type RING-HC finger and an ubiquitin-associated (UBA) domain.