Regulation of B cell fate by chronic activity of the IgE B cell receptor.

IgE can trigger potent allergic responses, yet the mechanisms regulating IgE production are poorly understood. Here we reveal that IgE+ B cells are constrained by chronic activity of the IgE B cell receptor (BCR). In the absence of cognate antigen, the IgE BCR promoted terminal differentiation of B cells into plasma cells (PCs) under cell culture conditions mimicking T cell help. This antigen-independent PC differentiation involved multiple IgE domains and Syk, CD19, BLNK, Btk, and IRF4. Disruption of BCR signaling in mice led to consistently exaggerated IgE+ germinal center (GC) B cell but variably increased PC responses. We were unable to confirm reports that the IgE BCR directly promoted intrinsic apoptosis. Instead, IgE+ GC B cells exhibited poor antigen presentation and prolonged cell cycles, suggesting reduced competition for T cell help. We propose that chronic BCR activity and access to T cell help play critical roles in regulating IgE responses

Ternatin and improved synthetic variants kill cancer cells by targeting the elongation factor-1A ternary complex.

Cyclic peptide natural products have evolved to exploit diverse protein targets, many of which control essential cellular processes. Inspired by a series of cyclic peptides with partially elucidated structures, we designed synthetic variants of ternatin, a cytotoxic and anti-adipogenic natural product whose molecular mode of action was unknown. The new ternatin variants are cytotoxic toward cancer cells, with up to 500-fold greater potency than ternatin itself. Using a ternatin photo-affinity probe, we identify the translation elongation factor-1A ternary complex (eEF1A·GTP·aminoacyl-tRNA) as a specific target and demonstrate competitive binding by the unrelated natural products, didemnin and cytotrienin. Mutations in domain III of eEF1A prevent ternatin binding and confer resistance to its cytotoxic effects, implicating the adjacent hydrophobic surface as a functional hot spot for eEF1A modulation. We conclude that the eukaryotic elongation factor-1A and its ternary complex with GTP and aminoacyl-tRNA are common targets for the evolution of cytotoxic natural products

A prospective study of physician-observed concussion during a varsity university ice hockey season: Incidence and neuropsychological changes. Part 2 of 4

Object: The primary objective of this study was to measure the incidence of concussion according to a relative number of athlete exposures among 25 male and 20 female varsity ice hockey players. The secondary objective was to present neuropsychological test results between preseason and postseason play and at 72 hours, 2 weeks, and 2 months after concussion. Methods: Every player underwent baseline assessments using the Sport Concussion Assessment Tool-2 (SCAT2), Immediate Post-Concussion Assessment and Cognitive Test (ImPACT), and MRI. Each regular season and postseason game was observed by 2 independent observers (a physician and a nonphysician observer). Players with a diagnosed concussion were removed from the game, examined in the team physician\u27s office using the SCAT2 and ImPACT, and sent to undergo MRI. Results: Eleven concussions occurred during the 55 physician-observed games (20%). The incidence of concussion, expressed as number of concussions per 1000 athlete exposures, was 10.70 for men and women combined in regular season play, 11.76 for men and women combined across both the regular season and playoff season, 7.50 for men and 14.93 for women in regular season play, and 8.47 for men across both the regular season and playoff season. One male player experienced repeat concussions. No concussions were reported during practice sessions, and 1 concussion was observed and diagnosed in an exhibition game. Neuropsychological testing suggested no statistically significant preseason/postseason differences between athletes who sustained a physician-diagnosed concussion and athletes who did not sustain a physician-diagnosed concussion on either the ImPACT or SCAT2. The athletes who sustained a physician-diagnosed concussion demonstrated few reliable changes postinjury. Conclusions: Although the incidence of game-related concussions per 1000 athlete exposures in this study was half the highest rate reported in the authors\u27 previous research, it was 3 times higher than the incidence reported by other authors within the literature concerning men\u27s collegiate ice hockey and 5 times higher than the highest rate previously reported for woman\u27s collegiate ice hockey. Interestingly, the present results suggest a substantively higher incidence of concussion among women (14.93) than men (7.50). The reproducible and significantly higher incidence of concussion among both men and woman ice hockey players, when compared with nonphysician-observed games, suggests a significant underestimation of sports concussion in the scientific literature

Repurposing tofacitinib as an anti-myeloma therapeutic to reverse growth-promoting effects of the bone marrow microenvironment.

The myeloma bone marrow microenvironment promotes proliferation of malignant plasma cells and resistance to therapy. Activation of JAK/STAT signaling is thought to be a central component of these microenvironment-induced phenotypes. In a prior drug repurposing screen, we identified tofacitinib, a pan-JAK inhibitor Food and Drug Administration (FDA) approved for rheumatoid arthritis, as an agent that may reverse the tumor-stimulating effects of bone marrow mesenchymal stromal cells. Herein, we validated in vitro, in stromal-responsive human myeloma cell lines, and in vivo, in orthotopic disseminated xenograft models of myeloma, that tofacitinib showed efficacy in myeloma models. Furthermore, tofacitinib strongly synergized with venetoclax in coculture with bone marrow stromal cells but not in monoculture. Surprisingly, we found that ruxolitinib, an FDA approved agent targeting JAK1 and JAK2, did not lead to the same anti-myeloma effects. Combination with a novel irreversible JAK3-selective inhibitor also did not enhance ruxolitinib effects. Transcriptome analysis and unbiased phosphoproteomics revealed that bone marrow stromal cells stimulate a JAK/STAT-mediated proliferative program in myeloma cells, and tofacitinib reversed the large majority of these pro-growth signals. Taken together, our results suggest that tofacitinib reverses the growth-promoting effects of the tumor microenvironment. As tofacitinib is already FDA approved, these results can be rapidly translated into potential clinical benefits for myeloma patients

Prolonged and tunable residence time using reversible covalent kinase inhibitors.

Drugs with prolonged on-target residence times often show superior efficacy, yet general strategies for optimizing drug-target residence time are lacking. Here we made progress toward this elusive goal by targeting a noncatalytic cysteine in Bruton's tyrosine kinase (BTK) with reversible covalent inhibitors. Using an inverted orientation of the cysteine-reactive cyanoacrylamide electrophile, we identified potent and selective BTK inhibitors that demonstrated biochemical residence times spanning from minutes to 7 d. An inverted cyanoacrylamide with prolonged residence time in vivo remained bound to BTK for more than 18 h after clearance from the circulation. The inverted cyanoacrylamide strategy was further used to discover fibroblast growth factor receptor (FGFR) kinase inhibitors with residence times of several days, demonstrating the generalizability of the approach. Targeting of noncatalytic cysteines with inverted cyanoacrylamides may serve as a broadly applicable platform that facilitates 'residence time by design', the ability to modulate and improve the duration of target engagement in vivo

p90RSK Targets the ERK5-CHIP Ubiquitin E3 Ligase Activity in Diabetic Hearts and Promotes Cardiac Apoptosis and Dysfunction

RATIONALE: Cardiomyocyte apoptosis is one of the key events in the development and progression of heart failure, and a crucial role for ICER (inducible cAMP early repressor) in this process has been previously reported. ERK5 is known to inhibit cardiac apoptosis after myocardial infarction (MI), especially in hyperglycemic states, via association with CHIP ubiquitin (Ub) ligase and subsequent up-regulation of CHIP ligase activity, which induces ICER ubiquitination and subsequent protein degradation. The regulatory mechanism governing ERK5/CHIP interaction is unknown. OBJECTIVE: We previously demonstrated increased p90RSK activation in the diabetic heart. As a logical extension of this work, we now investigate whether p90RSK activation inhibits ERK5-mediated CHIP activation, and subsequently increases ICER levels and apoptosis. METHODS AND RESULTS: p90RSK activation inhibits ERK5/CHIP association and CHIP Ub ligase activity. p90RSK and CHIP share a common binding site in the ERK5 C-terminal domain (aa571-807). Overexpression of either p90RSK or an ERK5 fragment (aa571-807) inhibits ERK5/CHIP association, suggesting that p90RSK and CHIP competes for ERK5 binding and that p90RSK activation is critical for inhibiting ERK5/CHIP interaction. We also identified ERK5-S496 as being directly phosphorylated by p90RSK, and demonstrated that an ERK5-S496A mutant significantly impairs Angiotensin II-mediated inhibition of CHIP activity and subsequent increase in ICER levels. In vivo, either cardiac specific depletion of ERK5 or overexpression of p90RSK inhibits CHIP activity and accelerates cardiac apoptosis after MI--a phenomenon fully reversible by activating ERK5. CONCLUSION: These data suggest a role for p90RSK in inhibiting CHIP activity and promoting cardiac apoptosis through binding to and phosphorylation of ERK5-S496

p90RSK Targets the ERK5-CHIP Ubiquitin E3 Ligase Activity in Diabetic Hearts and Promotes Cardiac Apoptosis and Dysfunction

Cardiomyocyte apoptosis is one of the key events in the development and progression of heart failure, and a crucial role for ICER (inducible cAMP early repressor) in this process has been previously reported. ERK5 is known to inhibit cardiac apoptosis after myocardial infarction (MI), especially in hyperglycemic states, via association with CHIP ubiquitin (Ub) ligase and subsequent up-regulation of CHIP ligase activity, which induces ICER ubiquitination and subsequent protein degradation. The regulatory mechanism governing ERK5/CHIP interaction is unknown

Recruitment and Activation of RSK2 by HIV-1 Tat

The transcriptional activity of the integrated HIV provirus is dependent on the chromatin organization of the viral promoter and the transactivator Tat. Tat recruits the cellular pTEFb complex and interacts with several chromatin-modifying enzymes, including the histone acetyltransferases p300 and PCAF. Here, we examined the interaction of Tat with activation-dependent histone kinases, including the p90 ribosomal S6 kinase 2 (RSK2). Dominant-negative RSK2 and treatment with a small-molecule inhibitor of RSK2 kinase activity inhibited the transcriptional activity of Tat, indicating that RSK2 is important for Tat function. Reconstitution of RSK2 in cells from subjects with a genetic defect in RSK2 expression (Coffin-Lowry syndrome) enhanced Tat transactivation. Tat interacted with RSK2 and activated RSK2 kinase activity in cells. Both properties were lost in a mutant Tat protein (F38A) that is deficient in HIV transactivation. Our data identify a novel reciprocal regulation of Tat and RSK2 function, which might serve to induce early changes in the chromatin organization of the HIV LTR

A SARS-CoV-2 protein interaction map reveals targets for drug repurposing

The novel coronavirus SARS-CoV-2, the causative agent of COVID-19 respiratory disease, has infected over 2.3 million people, killed over 160,000, and caused worldwide social and economic disruption1,2. There are currently no antiviral drugs with proven clinical efficacy, nor are there vaccines for its prevention, and these efforts are hampered by limited knowledge of the molecular details of SARS-CoV-2 infection. To address this, we cloned, tagged and expressed 26 of the 29 SARS-CoV-2 proteins in human cells and identified the human proteins physically associated with each using affinity-purification mass spectrometry (AP-MS), identifying 332 high-confidence SARS-CoV-2-human protein-protein interactions (PPIs). Among these, we identify 66 druggable human proteins or host factors targeted by 69 compounds (29 FDA-approved drugs, 12 drugs in clinical trials, and 28 preclinical compounds). Screening a subset of these in multiple viral assays identified two sets of pharmacological agents that displayed antiviral activity: inhibitors of mRNA translation and predicted regulators of the Sigma1 and Sigma2 receptors. Further studies of these host factor targeting agents, including their combination with drugs that directly target viral enzymes, could lead to a therapeutic regimen to treat COVID-19