Barboza, B. R. | Search bioRxiv

bioRxiv2022

ArtinM Cytotoxicity in B cells derived from Non-Hodgkins Lymphoma is regulated by CD45 phosphatase activity and Src family kinases

Receptors on the immune cell surface have a variety of glycans that may account for the immunomodulation induced by lectins, which have a carbohydrate recognition domain (CRD) that binds to monosaccharides or oligosaccharides in a specific manner. ArtinM, a D-mannose-binding lectin obtained from Artocarpus heterophyllus, has affinity for the N-glycans core. Immunomodulation by ArtinM toward the Th1 phenotype occurs via its interaction with TLR2/CD14 N-glycans on antigen-presenting cells, as well as recognition of CD3{gamma} N-glycans on murine CD4+ and CD8+ T cells. ArtinM exerts a cytotoxic effect on Jurkat human leukemic T cell line and human myeloid leukemia cell line (NB4). The current study evaluated the effects of ArtinM on murine and human B cells derived from non-Hodgkins lymphoma. We found that murine B cells are recognized by ArtinM via the CRD, and the ArtinM stimulus did not augment the proliferation rate or production of IL-2. However, murine B cells incubation with ArtinM augmented the rate of apoptosis, and this cytotoxic effect of ArtinM was also seen in human B cell lines sourced from non-Hodgkins lymphoma Raji cell line. This cytotoxic effect was inhibited by the phosphatase activity of CD45 on Lck, and the protein kinases of the Src family contribute to cell death triggered by ArtinM.

cell biology↗

bioRxiv2021

Protein arginylation is regulated during SARS-CoV-2 infection

In 2019, the world witnessed the onset of an unprecedented pandemic. In September 2021, the infection by SARS-CoV-2 had already been responsible for the death of more than 4 million people worldwide. Recently, we and other groups discovered that SARS-CoV-2 infection induces ER-stress and activation of unfolded protein response (UPR) pathway. The degradation of misfolded/unfolded proteins is an essential element of proteostasis and occurs mainly in lysosomes or proteasomes. The N-terminal arginylation of proteins is characterized as an inducer of ubiquitination and proteasomal degradation by the N-end rule pathway. Here we present, for the first time, data on the role of arginylation during SARS-CoV-2 infection. We studied the modulation of protein arginylation in Vero CCL-81 and Calu-3 cells infected after 2h, 6h, 12h, 24h, and 48h. A reanalysis of in vivo and in vitro public omics data combined with immunoblotting was performed to measure the levels of ATE1 and arginylated proteins. This regulation is seen specifically during infections by coronaviruses. We demonstrate that during SARS-CoV-2 infection there is an increase in the expression of the ATE1 enzyme associated with regulated levels of specific arginylated proteins. On the other hand, infected macrophages showed no ATE1 regulation. An important finding revealed that modulation of the N-end rule pathway differs between different types of infected cells. We also confirmed the potential of tannic acid to reduce viral load, and furthermore, to modulate ATE1 levels during infection. In addition, the arginylation inhibitor merbromin (MER) is also capable of both reducing viral load and reducing ATE1 levels. Taken together, these data show the importance of arginylation during the progression of SARS-CoV-2 infection and open the door for future studies that may unravel the role of ATE1 and its inhibitors in pathogen infection.

cell biology↗