A tyrosine phosphorylation switch controls the interaction between the transmembrane modulator protein Wzd and the tyrosine kinase Wze of Lactobacillus rhamnosus

Background: One proposed mechanism for assembly of secreted heteropolysaccharides by many Gram positive bacteria relies on the coordinated action of a polymerization complex through reversible phosphorylation events. The role of the tyrosine protein kinase transmembrane modulator is, however, not well understood. Results: The protein sequences deduced from the wzb, wzd and wze genes from Lactobacillus rhamnosus ATCC 9595 and RW-9595 M contain motifs also found in corresponding proteins CpsB, CpsC and CpsD from Streptococcus pneumoniae D39 (serotype 2). Use of an anti-phosphotyrosine antibody demonstrated that both Wzd and Wze can be found in tyrosine phosphorylated form. When tyrosine 266 was mutated to phenylalanine, WzdY266F showed slightly less phosphorylated protein than those produced by using eight other tyrosine mutated Wzd genes, when expressed along with Wze and Wzb in Lactococcus lactis subsp. cremoris MG1363. In order to demonstrate the importance of ATP for the interactions among these proteins, native and fusion Wzb, Wzd and Wze proteins were expressed and purified from Escherichia coli cultures. The modulator protein, Wzd, binds with the phosphotyrosine kinase Wze, irrespective of its phosphorylation status. However, Wze attained a higher phosphorylation level after interacting with phosphorylated Wzd in the presence of 10 mM ATP. This highly phosphorylated Wze did not remain in close association with phosphorylated Wzd. Conclusion: The Wze tyrosine kinase protein of Lactobacillus rhamnosus thus carries out tyrosine phosphorylation of Wzd in addition to auto- and trans- phosphorylation of the kinase itself © BioMed Central101sciescopu

Arginase therapy combines effectively with checkpoint blockade or agonist anti-OX40 immunotherapy to control tumor growth.

Metabolic dysregulation is a hallmark of cancer; for instance, many tumors exhibit auxotrophy for various amino acids, such as arginine, as they are unable to meet the demand for these amino acids through endogenous production. This vulnerability can be exploited by employing therapeutic strategies that deplete systemic arginine in order to limit the growth and survival of arginine auxotrophic tumors. Pegzilarginase, a human arginase 1 enzyme engineered to have superior stability and enzymatic activity relative to the native human arginase 1 enzyme, depletes systemic arginine by converting it to ornithine and urea. Therapeutic administration of pegzilarginase in the setting of arginine auxotrophic tumors exerts direct anti-tumor activity by starving the tumor of exogenous arginine. We hypothesized that in addition to this direct effect, pegzilarginase treatment indirectly augments anti-tumor immunity through increased antigen presentation, thus making pegzilarginase a prime candidate for combination therapy with immuno-oncology (I-O) agents. Indeed, tumor-bearing mice (CT26; MC38; MCA-205) receiving pegzilarginase in combination with aPD-L1 or agonist aOX40 mAb experienced significantly increased survival relative to animals receiving I-O monotherapy. Combination pegzilarginase/immunotherapy induced robust anti-tumor immunity characterized by increased intratumoral effector CD8+ T cells and M1-polarization of tumor-associated macrophages. Our data suggests potential mechanisms of synergy between pegzilarginase and I-O agents that include increased intratumoral MHC expression on both APCs and tumor cells, and increased presence of M1-like anti-tumor macrophages. These data support the clinical evaluation of I-O agents in conjunction with pegzilarginase for the treatment of patients with cancer