A proximity-dependent biotinylation (BioID) approach flags the p62/sequestosome-1 protein as a caspase-1 substrate.

The inflammasome is a major component of the innate immune system, and its main function is to activate caspase-1, a cysteine protease that promotes inflammation by inducing interleukin-1ß (IL-1ß) maturation and release into the extracellular milieu. To prevent uncontrolled inflammation, this complex is highly regulated. When it is assembled, the inflammasome is insoluble, which has long precluded the analysis of its interactions with other proteins. Here we used the proximity-dependent biotinylation assay (BioID) to identify proteins associated with caspase-1 during inflammasome activation. Using the BioID in a cell-free system in which the inflammasome had been activated, we found that a caspase-1-biotin ligase fusion protein selectively labeled 111 candidates, including the p62/sequestosome-1 protein (p62). Using co-immunoprecipitation experiments, we demonstrated that p62 interacts with caspase-1. This interaction promoted caspase-1-mediated cleavage of p62 at Asp-329. Mechanistic and functional analyses revealed that caspase-1-mediated cleavage of p62 leads to loss of its interaction with the autophagosomal protein microtubule-associated protein 1 light chain 3 ß (LC3B). Strikingly, overexpression of a p62 N-terminal fragment generated upon caspase-1 cleavage decreased IL-1ß release, whereas overexpression of p62's C-terminal portion enhanced IL-1ß release, by regulating pro-IL1ß levels. Overall, the overexpression of both fragments together decreased IL-1ß release. Taken together, our results indicate that caspase-1-mediated p62 cleavage plays a complex role in balancing caspase-1-induced inflammation.

An inhibitor of HIV-1 protease modulates constitutive eIF2α dephosphorylation to trigger a specific integrated stress response.

Inhibitors of the HIV aspartyl protease [HIV protease inhibitors (HIV-PIs)] are the cornerstone of treatment for HIV. Beyond their well-defined antiretroviral activity, these drugs have additional effects that modulate cell viability and homeostasis. However, little is known about the virus-independent pathways engaged by these molecules. Here we show that the HIV-PI Nelfinavir decreases translation rates and promotes a transcriptional program characteristic of the integrated stress response (ISR). Mice treated with Nelfinavir display hallmarks of this stress response in the liver, including α subunit of translation initiation factor 2 (eIF2α) phosphorylation, activating transcription factor-4 (ATF4) induction, and increased expression of known downstream targets. Mechanistically, Nelfinavir-mediated ISR bypassed direct activation of the eIF2α stress kinases and instead relied on the inhibition of the constitutive eIF2α dephosphorylation and down-regulation of the phophatase cofactor CReP (Constitutive Repressor of eIF2α Phosphorylation; also known as PPP1R15B). These findings demonstrate that the modulation of eIF2α-specific phosphatase cofactor activity can be a rheostat of cellular homeostasis that initiates a functional ISR and suggest that the HIV-PIs could be repositioned as therapeutics in human diseases to modulate translation rates and stress responses.

AIM2 inflammasome is activated by pharmacological disruption of nuclear envelope integrity.

Inflammasomes are critical sensors that convey cellular stress and pathogen presence to the immune system by activating inflammatory caspases and cytokines such as IL-1ß. The nature of endogenous stress signals that activate inflammasomes remains unclear. Here we show that an inhibitor of the HIV aspartyl protease, Nelfinavir, triggers inflammasome formation and elicits an IL-1R-dependent inflammation in mice. We found that Nelfinavir impaired the maturation of lamin A, a structural component of the nuclear envelope, thereby promoting the release of DNA in the cytosol. Moreover, deficiency of the cytosolic DNA-sensor AIM2 impaired Nelfinavir-mediated inflammasome activation. These findings identify a pharmacologic activator of inflammasome and demonstrate the role of AIM2 in detecting endogenous DNA release upon perturbation of nuclear envelope integrity.

A Noninterventional, Observational, European Post-Authorization Safety Study of Patients With Relapsed/Refractory Multiple Myeloma Treated With Lenalidomide.

INTRODUCTION: Lenalidomide plus dexamethasone is effective and well tolerated in relapsed/refractory multiple myeloma (RRMM). In this observational, noninterventional European post-authorization safety study, the safety profile of lenalidomide plus dexamethasone was investigated and compared with that of other agents in the treatment of RRMM in a real-world setting. PATIENTS AND METHODS: Patients had received ≥ 1 prior antimyeloma therapy; prior lenalidomide was excluded. Treatment was per investigator's routine practice. Adverse events were analyzed by incidence rates per 100 person-years to account for differences in observation length and treatment duration. RESULTS: In total, 2150 patients initiated lenalidomide, and 1479 initiated any other antimyeloma therapy, predominately bortezomib (80.3%), which was primarily administered intravenously (74.3%). The incidence rate of neuropathy was lower with lenalidomide (10.5) than with bortezomib (78.9) or thalidomide (38.7). Lenalidomide also had a lower incidence rate of infections (68.7) versus bortezomib (95.9) and thalidomide (76.0). Conversely, the incidence rate of neutropenia was higher with lenalidomide (38.0) than with bortezomib (18.2) or thalidomide (25.7). The incidence rates of thrombocytopenia were 24.4, 40.4, and 14.4 with lenalidomide, bortezomib, and thalidomide, respectively. CONCLUSION: No new safety signals for lenalidomide were identified in this study, which is the largest prospective real-world European study of lenalidomide in patients with RRMM to date. These results confirm that the safety profile of lenalidomide plus dexamethasone in RRMM in a real-world setting is comparable to that reported in clinical trials.

Pomalidomide Plus Low-Dose Dexamethasone in Patients With Relapsed/Refractory Multiple Myeloma and Renal Impairment: Results From a Phase II Trial.

Purpose Renal impairment (RI) limits treatment options in patients with relapsed/refractory multiple myeloma (RRMM). Here, we prospectively studied pomalidomide plus low-dose dexamethasone (LoDEX) in patients with RRMM and moderate or severe RI, including those receiving hemodialysis. Patients and Methods MM-013, a noncomparative, European phase II trial, enrolled three patient cohorts: moderate RI (cohort A; estimated glomerular filtration rate, 30 to < 45 mL/min/1.73 m2); severe RI (cohort B; estimated glomerular filtration rate, < 30 mL/min/1.73 m2); and severe RI that requires hemodialysis (cohort C). Patients received pomalidomide 4 mg/d on days 1 to 21 and LoDEX 20 or 40 mg once per week in 28-day cycles. The primary end point was overall response rate. Results Of 81 enrolled patients (33, 34, and 14 patients in cohorts A, B, and C, respectively), 13 were still receiving treatment at data cutoff (January 28, 2017). Overall response rates were 39.4%, 32.4%, and 14.3%, with a median duration of response of 14.7 months, 4.6 months, and not estimable, respectively. Of importance, 100%, 79.4%, and 78.6% of patients, respectively, achieved disease control. With a median follow-up of 8.6 months, median overall survival was 16.4 months, 11.8 months, and 5.2 months, respectively. Complete renal responses were observed only in cohort A (18.2%), and no patients in cohort C became hemodialysis independent. Grade 3 and 4 hematologic treatment-emergent adverse events and pomalidomide discontinuations as a result of treatment-emergent adverse events occurred more frequently in cohort C. Pomalidomide pharmacokinetics were comparable among the three renal cohorts. Conclusion Pomalidomide 4 mg/d plus LoDEX is efficacious in patients with RRMM with moderate or severe RI, including those who had more advanced disease and required hemodialysis. The safety profile was acceptable among the three groups, and no new safety signals were observed.