Related Experiment Video
Updated: Feb 26, 2026
Intracellular Phosphoflow Cytometry of Acute Myeloid Leukemia Patient-Derived Xenotransplants
Published on: June 6, 2025
Mercury alters endogenous phosphorylation profiles of SYK in murine B cells
Joseph A Caruso1, Nicholas Carruthers2, Namhee Shin2
1Institute of Environmental Health Sciences, Center for Urban Responses to Environmental Stressors (CURES), Wayne State University, Detroit, MI, 48201, USA. joseph_caruso@wayne.edu.
Background:
Epidemiological evidence and animal models suggest that exposure to low and non-neurotoxic concentrations of mercury may contribute to idiosyncratic autoimmune disease. Since defects in function and signaling in B cells are often associated with autoimmunity, we investigated whether mercury exposure might alter B cell responsiveness to self-antigens by interfering with B cell receptor (BCR) signal transduction. In this study we determined the effects of mercury on the protein tyrosine kinase SYK, a critical protein involved in regulation of the BCR signaling pathway.
Methods:
Phosphorylation sites of murine SYK were mapped before and after treatment of WEHI cell cultures with mercury, or with anti-IgM antibody (positive control) or pervanadate (a potent phosphatase inhibitor). Phosphopeptides were enriched by either titanium dioxide chromatography or anti-phosphotyrosine immunoaffinity, and analyzed by liquid chromatography-mass spectrometry. Select SYK phosphosite cluster regions were profiled for responsiveness to treatments using multiple reaction monitoring (MRM) methodology.
Results:
A total of 23 phosphosites were identified with high probability in endogenous SYK, including 19 tyrosine and 4 serine residues. For 10 of these sites phosphorylation levels were increased following BCR activation. Using MRM to profile changes in phosphorylation status we found that 4 cluster regions, encompassing 8 phosphosites, were activated by mercury and differentially responsive to all 3 treatments. Phosphorylation of tyrosine-342 and -346 residues were most sensitive to mercury exposure. This cluster is known to propagate normal BCR signal transduction by recruiting adaptor proteins such as PLC-γ and Vav-1 to SYK during formation of the BCR signalosome.
Conclusions:
Our data shows that mercury alters the phosphorylation status of SYK on tyrosine sites known to have a role in promoting BCR signals. Considering the importance of SYK in the BCR signaling pathway, these data suggest that mercury can alter BCR signaling in B cells, which might affect B cell responsiveness to self-antigen and have implications with respect to autoimmunity and autoimmune disease.
