Biology subjects

Shalah, R.

Publications and source records attributed to Shalah, R..

2 recordsLinked to original sources

bioRxiv2023

Multiple Thymic Cell Fate Decisions Regulated by Gads

Thymic development is tightly regulated by TCR signaling via the immune adaptors SLP-76 and LAT. Gads bridges the TCR-induced recruitment of SLP-76 to LAT; yet is not absolutely required for thymic progression. To better identify Gads-dependent developmental transitions, we performed tamoxifen-induced ablation of Gads (GadsiKO), accompanied by expression of tdTomato, and compared the development of Gads-expressing (Tom-) and - ablated (Tom+) thymocytes within the same mouse. The frequency of GadsiKO (Tom+) thymocytes decreased at {beta}-selection and positive selection, confirming the Gads-dependence of these junctures; nevertheless, we observed small populations of positively-selected GadsiKO SP thymocytes. Consistent with a signaling defect, expression of CD5 was strongly impaired at the {beta}-selection checkpoint and within the DP compartment; moreover, GadsiKO DP thymocytes exhibited reduced TCR-induced calcium flux. Surprisingly, MHC-non-responding (CD5-) GadsiKO DP thymocytes exhibited reduced death by neglect; instead, aberrant populations of CD5- GadsiKO thymocytes progressed as far as the CD4 SP compartment, while lacking key characteristics of positively selected thymocytes. In an experimentally-induced model of death by neglect triggered by CD8 crosslinking, Gads was required for the preferential apoptosis of CD5lo DP thymocytes. Our results suggest that Gads promotes passage through TCR-driven developmental checkpoints while also promoting the death by neglect of unselected thymocytes.

immunology↗

bioRxiv2020

Itk promotes the integration of TCR and CD28 costimulation, through its direct substrates, SLP-76 and Gads

The costimulatory receptor, CD28, synergizes with the T cell antigen receptor (TCR) to promote IL-2 production, cell survival and proliferation. Despite their profound synergy, the obligatory interdependence of the signaling pathways initiated by these two receptors is not well understood. Upon TCR stimulation, Gads, a Grb2-family adaptor, bridges the interaction of two additional adaptors, LAT and SLP-76, to form a TCR-induced effector signaling complex. SLP-76 binds the Tec-family tyrosine kinase, Itk, which phosphorylates SLP-76 at Y173 and PLC-{gamma}1 at Y783. Here we identified Gads Y45 as an additional TCR-inducible, Itk-mediated phosphorylation site. Y45 is found within the N-terminal SH3 domain of Gads, an evolutionarily conserved domain with no known binding partners or signaling function. Gads Y45 phosphorylation depended on the interaction of Gads with SLP-76 and on the preferentially-paired binding of Gads to phospho-LAT. Three Itk-related features, Gads Y45, SLP-76 Y173, and a proline-rich Itk SH3-binding motif on SLP-76, were selectively required for activation of the CD28 RE/AP transcriptional element from the IL-2 promoter, but were not required to activate NFAT. This study illuminates a new regulatory module, in which Itk-targeted phosphorylation sites on two adaptor proteins, SLP-76 and Gads, control the transcriptional response to TCR/CD28 costimulation, thus enforcing the obligatory interdependence of the TCR and CD28 signaling pathways.

immunology↗