The Deubiquitylase Otub1 Regulates the Chemotactic Response of Splenic B Cells by Modulating the Stability of the γ-Subunit Gng2.

The ubiquitin proteasome system performs the covalent attachment of lysine 48-linked polyubiquitin chains to substrate proteins, thereby targeting them for degradation, while deubiquitylating enzymes (DUBs) reverse this process. This posttranslational modification regulates key features both of innate and adaptative immunity, including antigen presentation, protein homeostasis and signal transduction. Here we show that loss of one of the most highly expressed DUBs, Otub1, results in changes in murine splenic B cell subsets, leading to a significant increase in marginal zone and transitional B cells and a concomitant decrease in follicular B cells. We demonstrate that Otub1 interacts with the γ-subunit of the heterotrimeric G protein, Gng2, and modulates its ubiquitylation status, thereby controlling Gng2 stability. Proximal mapping of Gng2 revealed an enrichment in partners associated with chemokine signaling, actin cytoskeleton and cell migration. In line with these findings, we show that Otub1-deficient B cells exhibit greater Ca2+ mobilization, F-actin polymerization and chemotactic responsiveness to Cxcl12, Cxcl13 and S1P in vitro, which manifests in vivo as altered localization of B cells within the spleen. Together, our data establishes Otub1 as a novel regulator of G-protein coupled receptor signaling in B cells, regulating their differentiation and positioning in the spleen.

Frequency of Kell and Rh alloantibodies in Iranian Thalassemia Patients in Khorasan Razavi Province, Iran.

Background: Thalassemia is an inherited disease with anemia and hemolysis. Blood transfusion is a routine treatment for thalassemia patients; alloimmunization is one of the complications of blood transfusion, which is very serious for these patients, especially girls and young women. Materials and Methods: In this cross-sectional study, 446 thalassemia patients were examined. Demographic information of patients was extracted and recorded. The phenotype of ABO, Rh, and Kell antigens (tube method) with antisera from IMMUNDIANOSTICA Company (Germany) and the frequency of alloantibodies were determined. Results: 55.8% of the studied individuals were male, and 44.2% were female. Mean age of the studied patients was 19.94±10.63. The alloantibodies were detected in 7.5% of cell-pack receivers. The most prevalent phenotype of the ABO system was the O blood group (37.4%), and the most abundant antigen of the Rh group was 'e', which was found in 99.8% of the studied population. The most common alloantibody detected was Anti K (38.2%); concerning kell phenotype, (K_k+) and (K+k+) were found in 99.3% and 0.7% of patients, respectively. The frequency of Anti-D, Anti-C, Anti-c, and Anti-E was 23.5%, 14.7%, 2.9%, and 14.7%, respectively. Conclusion: According to the results of this paper, finding the compatible packed cells in terms of Kell and Rh systems antigens in addition to the ABO blood group is recommended to decrease the rate of alloantibodies in thalassemia patients.

The mitochondrial pyruvate carrier complex potentiates the efficacy of proteasome inhibitors in multiple myeloma.

Multiple myeloma (MM) is a hematological malignancy that emerges from antibody-producing plasma B cells. Proteasome inhibitors, including the US Food and Drug Administration-approved bortezomib (BTZ) and carfilzomib (CFZ), are frequently used for the treatment of patients with MM. Nevertheless, a significant proportion of patients with MM are refractory or develop resistance to this class of inhibitors, which represents a significant challenge in the clinic. Thus, identifying factors that determine the potency of proteasome inhibitors in MM is of paramount importance to bolster their efficacy in the clinic. Using genome-wide CRISPR-based screening, we identified a subunit of the mitochondrial pyruvate carrier (MPC) complex, MPC1, as a common modulator of BTZ response in 2 distinct human MM cell lines in vitro. We noticed that CRISPR-mediated deletion or pharmacological inhibition of the MPC complex enhanced BTZ/CFZ-induced MM cell death with minimal impact on cell cycle progression. In fact, targeting the MPC complex compromised the bioenergetic capacity of MM cells, which is accompanied by reduced proteasomal activity, thereby exacerbating BTZ-induced cytotoxicity in vitro. Importantly, we observed that the RNA expression levels of several regulators of pyruvate metabolism were altered in advanced stages of MM for which they correlated with poor patient prognosis. Collectively, this study highlights the importance of the MPC complex for the survival of MM cells and their responses to proteasome inhibitors. These findings establish mitochondrial pyruvate metabolism as a potential target for the treatment of MM and an unappreciated strategy to increase the efficacy of proteasome inhibitors in the clinic.