T cells and mast cells share a high sensitivity to antigen. In both cell types, antigen recognition triggers the tyrosine phosphorylation of two key adaptor proteins, LAT and SLP-76. A third adaptor, Gads, bridges the recruitment of SLP-76 to LAT, and together these adaptors nucleate the formation of large signaling complexes that transmit antigen receptor signals into the cell.
Our group studies the regulatory mechanisms that govern adaptor protein signaling pathways. We characterized the role of SLP-76 in recruiting and activating specific kinases that regulate antigen receptor responsiveness. We identified and characterized new phosphorylation sites on SLP-76 and Gads that regulate their signaling functions. We are studying cooperative interactions within the LAT-nucleated signaling complex, and the role of SH2 domain dimerization in mediating cooperativity. Our research combines biochemical, biophysical and genetic approaches to reach an in depth understanding of the mechanisms underlying the sensitivity and selectivity of antigen responsiveness.
Gads exerts complex regulatory effects on T cell development and function. To better understand its regulatory roles we have developed new mouse models, with which we can inducibly delete Gads, or to allow expression of unique Gads point mutants in vivo. These mouse models are increasingly integrated into our research and provide a systemic perspective on the regulatory roles exerted by Gads at various stages in the life of a T cell.
Gads dimerization promotes its cooperative binding to LAT, which markedly increases the sensitivity of immune cell signaling. Here, TIRF microscopy was used to visualize the antigen receptor-induced co-clustering of Gads and LAT. We are using this approach as one way of characterizing the protein interfaces required for Gads dimerization, and for its cooperative binding to LAT.
Gads plays an important regulatory role in allergy; indeed, we showed that Gads dimerization is required for allergic responsiveness in a mouse model. We are developing new biophysical assays with which to characterize Gads dimerization and its cooperative binding to LAT. This research direction may lead to the development of novel strategies for the treatment of allergy.