SLAP2 Adaptor Binding Disrupts c-CBL Autoinhibition to Activate Ubiquitin Ligase Function.
CBL is a RING type E3 ubiquitin ligase that functions as a negative regulator of tyrosine kinase signaling and loss of CBL E3 function is implicated in several forms of leukemia. The Src-like adaptor proteins (SLAP/SLAP2) bind to CBL and are required for CBL-dependent downregulation of antigen receptor, cytokine receptor, ... and receptor tyrosine kinase signaling. Despite the established role of SLAP/SLAP2 in regulating CBL activity, the nature of the interaction and the mechanisms involved are not known. To understand the molecular basis of the interaction between SLAP/SLAP2 and CBL, we solved the crystal structure of CBL tyrosine kinase binding domain (TKBD) in complex with SLAP2. The carboxy-terminal region of SLAP2 adopts an ?-helical structure which binds in a cleft between the 4H, EF-hand, and SH2 domains of the TKBD. This SLAP2 binding site is remote from the canonical TKBD phospho-tyrosine peptide binding site but overlaps with a region important for stabilizing CBL in its autoinhibited conformation. In addition, binding of SLAP2 to CBL in vitro activates the ubiquitin ligase function of autoinhibited CBL. Disruption of the CBL/SLAP2 interface through mutagenesis demonstrated a role for this protein-protein interaction in regulation of CBL E3 ligase activity in cells. Our results reveal that SLAP2 binding to a regulatory cleft of the TKBD provides an alternative mechanism for activation of CBL ubiquitin ligase function.
Mesh Terms:
Adaptor Proteins, Signal Transducing, Binding Sites, Down-Regulation, Humans, Molecular Conformation, Protein Binding, Protein Interaction Domains and Motifs, Protein-Tyrosine Kinases, Proto-Oncogene Proteins c-cbl, Proto-Oncogene Proteins pp60(c-src), Receptor Protein-Tyrosine Kinases, Sequence Alignment, Signal Transduction, Ubiquitin, Ubiquitin-Protein Ligases, src Homology Domains
Adaptor Proteins, Signal Transducing, Binding Sites, Down-Regulation, Humans, Molecular Conformation, Protein Binding, Protein Interaction Domains and Motifs, Protein-Tyrosine Kinases, Proto-Oncogene Proteins c-cbl, Proto-Oncogene Proteins pp60(c-src), Receptor Protein-Tyrosine Kinases, Sequence Alignment, Signal Transduction, Ubiquitin, Ubiquitin-Protein Ligases, src Homology Domains
J Mol Biol
Date: Dec. 16, 2020
PubMed ID: 33617900
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