Src-like adaptor protein regulates TCR expression on thymocytes by linking the ubiquitin ligase c-Cbl to the TCR complex

Abstract

The adaptor molecule SLAP and E3 ubiquitin ligase c-Cbl each regulate expression of T cell receptor (TCR)-CD3 on thymocytes. Here we provide genetic and biochemical evidence that both molecules function in the same pathway. TCR-CD3 expression was similar in the absence of SLAP and/or c-Cbl. SLAP and c-Cbl were found to interact, and their expression together downregulated CD3epsilon. This required multiple domains in SLAP and the ring finger of c-Cbl. Furthermore, expression of SLAP and c-Cbl together induced TCRzeta ubiquitination and degradation, preventing the accumulation of fully assembled recycling TCR complexes. These studies indicate that SLAP links the E3 ligase activity of c-Cbl to the TCR, allowing for stage-specific regulation of TCR expression.

The tyrosine phosphatase SHP‐2 regulates differentiation and apoptosis of individual primary T lymphocytes

“…We speculate that this interaction is mediated by tyrosine residues in the C-terminal tail of SHP-2 that constitute potential binding sites for the atypical SH2 domains of c-Cbl. Both, c-Cbl and Cbl-b, are known to be involved in negative regulation of T cell function [48][49][50][51][52]. However, despite the possible interaction of SHP-2 with c-Cbl and Cbl-b in 293T cells, in WT Th cells we were only able to detect the interaction between SHP-2 and c-Cbl but not Cbl-b (Fig.…”

“…The interaction between SHP-2 and c-Cbl has been described earlier [44,45], but effects of this interaction for T cell function has not been shown to date. Potential target molecules of SHP-2/Cbl complex in T cells that are located upstream of PKC in the TCR signal transduction cascade are CD3-e, CD3-f, Lck, ZAP-70 or in particular PI3K [52][53][54][55][56][57]. By targeting one or more of these molecules for ubiquitin-mediated degradation, the increased complex formation between SHP-2 and c-Cbl could account for reduced effector function in full-length SHP-2-transduced Th cells.…”

Src-like adaptor protein (SLAP) regulates B cell receptor levels in a c-Cbl-dependent manner

“…The SLAP-deficient, c-Cbl-deficient, and SLAP c-Cbl doubly deficient mice have been described previously (8,14,16). The mice were backcrossed to C57BL/6 (B6) for at least five generations.…”

“…Recent work in our laboratory has shown that SLAP is required for c-Cbl-dependent down-modulation of the TCR complex in DP thymocytes (16). As a complement to these studies, we wanted to determine whether SLAP could cooperate with c-Cbl to down-modulate the BCR complex in B cells.…”

“…Interestingly, mice deficient in c-Cbl, SLAP, or both have similar thymic phenotypes, suggesting that SLAP and c-Cbl may function in the same biochemical pathway (14)(15)(16). Mice deficient in c-Cbl have alterations in B cell development with increased numbers of B1 B cells in the peritoneal cavity and increased immature B cell numbers in the spleen (17).…”