Comparative analyses of differentially induced T-cell receptor-mediated phosphorylation pathways in T lymphoma cells

Abstract

Activation of T lymphoma cells expressing Syk, but not ZAP-70 tyrosine kinase, has been shown to negatively regulate cell activation and activation induced cell death (AICD), perhaps due to differential induction of tyrosine phosphorylation modified proteins. To better understand the role of these proteins and their associated molecules/pathways, we studied a previously described model of T lymphoma cells expressing either a kinase-activated chimeric Syk or ZAP-70 genetically linked to TCR ζ chain (Z/Syk or Z/ZAP cells, respectively). To help identify molecules and pathways linked to cell activation or AICD, a comparative semi-quantitative proteomics-based approach was utilized to analyze tyrosine phosphorylated protein immunoprecipitates from 2 min short-term activated Z/Syk or Z/ZAP cells. Using the resulting bioinformatics datasets, we identified several differentially immunoprecipitated proteins that could be validated biochemically. More tyrosine-phosphorylated and phosphotyrosine-associated proteins were found in Z/Syk than in Z/ZAP cells. Proteins involved in different unique functional pathways were induced in these cells and showed altered intermolecular interactions in varied pathways. Remarkably, 41% of differentially identified proteins in Z/Syk cells belonged to cell cycle or vesicle/trafficking pathways. In contrast, 21% of such proteins in Z/ZAP cells belonged to metabolism pathways. Therefore, molecular pathways involved in post-translational modifications linked to distinct cellular/physiological functions are differentially activated, which may contribute to varied activation and AICD responses of these cells. In summary, we identified proteins belonging to novel differentially activated pathways involved in TCR-mediated signaling, which may be targets for regulating activation and AICD of T lymphoma cells and for potential cancer therapy.

SYK expression in monomorphic epitheliotropic intestinal T-cell lymphoma

“…It is a non-receptor type protein tyrosine kinase which is structurally and functionally related to ZAP-70 and under physiological conditions usually not expressed in mature T-cells. 39 SYK has already been a subject of investigation in T-cell lymphoma research, [40][41][42][43][44][45][46][47][48] although it has not been studied extensively in MEITL and EATL to date. 12,49 We here show a marked cytoplasmic expression of SYK in almost all MEITL cases (38/40), while the EATL cases displayed a consistent negativity for SYK (0/27).…”