Year: 2025
Type: dissertation
Abstract: Background: Gain of function Spleen Tyrosine Kinase (SYK) variants have been previously identified as a cause of systemic inflammation and immune dysregulation. This study aims to characterize novel SYK variants and review clinical phenotypes in a large cohort of patients. It further aims to understand the mechanism by which SYK gain of function variants dysregulate intracellular signaling and how this contributes to inflammatory disease. Methods: We identified patients with putative gain of function SYK variants and used cell based assays in HEK293T and LS174T-W4 intestinal epithelial cell lines to validate SYK gain of function. We also used co-immunoprecipitation to investigate interaction with receptors, and SYK inhibitors to ameliorate SYK gain of function. Using a BioID screen, we identified SYK interactors and further investigated a promising candidate, USP25, using western blots, co immunoprecipitation, luciferase assays, and ELISAs to investigate the functional impact of SYK gain of function on inflammatory signaling pathways. ii Results: Overall, we identified 18 patients harboring 1 of 12 SYK gain of function variants. Seven novel SYK variants were classified as gain of function based on constitutive phosphorylation at baseline in a cellular assay and one displayed differential phosphorylation in the different cell lines tested, based on its interaction with a pathogen recognition receptor Dectin-1. Furthermore, the SYK inhibitor Entospletinib was found to be a potential therapeutic option in SYK gain of function patients. Review of clinical features expanded the phenotype from asymptomatic carriers who may develop disease later in life to severe disease resulting in mortality. Characterizing the SYK-USP25 interaction identified that SYK phosphorylates USP25 leading to its degradation through the lysosomal pathway. Furthermore, in SYK gain of function cells, inflammatory signaling remains activated longer than WT cells, due to the role of USP25 as a negative regulator of inflammatory signaling, suggesting that SYK gain of function can cause inflammation by impairing cells’ ability to deactivate inflammatory signaling pathways. Conclusion: Here we report novel clinical phenotypes for patients carrying gain of function SYK variants and expands our knowledge of SYK variants into other protein domains. We also report a novel pathway by which SYK regulates inflammation.
Source: TSpace (University of Toronto)
Author: Natu, Amogh
Institution: University of Toronto
Language: English
Subfield: Immunology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7132858706