SummaryClearing senescent cells extends healthspan in mice. Using a hypothesis‐driven bioinformatics‐based approach, we recently identified pro‐survival pathways in human senescent cells that contribute to their resistance to apoptosis. This led to identification of dasatinib (D) and quercetin (Q) as senolytics, agents that target some of these pathways and induce apoptosis preferentially in senescent cells. Among other pro‐survival regulators identified was Bcl‐xl. Here, we tested whether the Bcl‐2 family inhibitors, navitoclax (N) and TW‐37 (T), are senolytic. Like D and Q, N is senolytic in some, but not all types of senescent cells: N reduced viability of senescent human umbilical vein epithelial cells (HUVECs), IMR90 human lung fibroblasts, and murine embryonic fibroblasts (MEFs), but not human primary preadipocytes, consistent with our previous finding that Bcl‐xl siRNA is senolytic in HUVECs, but not preadipocytes. In contrast, T had little senolytic activity. N targets Bcl‐2, Bcl‐xl, and Bcl‐w, while T targets Bcl‐2, Bcl‐xl, and Mcl‐1. The combination of Bcl‐2, Bcl‐xl, and Bcl‐w siRNAs was senolytic in HUVECs and IMR90 cells, while combination of Bcl‐2, Bcl‐xl, and Mcl‐1 siRNAs was not. Susceptibility to N correlated with patterns of Bcl‐2 family member proteins in different types of human senescent cells, as has been found in predicting response of cancers to N. Thus, N is senolytic and acts in a potentially predictable cell type‐restricted manner. The hypothesis‐driven, bioinformatics‐based approach we used to discover that dasatinib (D) and quercetin (Q) are senolytic can be extended to increase the repertoire of senolytic drugs, including additional cell type‐specific senolytic agents.

The COMMD1 protein, implicated in copper homeostasis, is found to regulate endosomal sorting of the copper transporter ATP7A through a novel protein complex containing CCDC22, CCDC93, and C16orf62, which link COMMD1 to the WASH complex.

Interaction between the hydrophobic Bak BH3-binding groove and the BH3 domain of activator proteins is a key step in initiating Bak oligomerization and activation.

Many chemotherapy treatments induce apoptosis or pyroptosis through BAK/BAX-dependent mitochondrial pathway. BAK/BAX activation causes the mitochondrial outer membrane permeabilization (MOMP), which induces the activation of pro-apoptotic caspase cascade. GSDME cleavage by the pro-apoptotic caspases determines whether chemotherapy drug treatments induce apoptosis or pyroptosis, however, its regulation mechanisms are not clear. In this study, we showed that TNFα+CHX and navitoclax-induced cancer cell pyroptosis through a BAK/BAX-caspase-3-GSDME signaling pathway. GSDME knockdown inhibited the pyroptosis, suggesting the essential role of GSDME in this process. Interestingly, GSDME was found to be palmitoylated on its C-terminal (GSDME-C) during chemotherapyinduced pyroptosis, while 2-bromopalmitate (2-BP) could inhibit the GSDME-C palmitoylation and chemotherapyinduced pyroptosis. Mutation of palmitoylation sites on GSDME also diminished the pyroptosis induced by chemotherapy drugs. Moreover, 2-BP treatment increased the interaction between GSDME-C and GSDME-N, providing a potential mechanism of this function. Further studies indicated several ZDHHC proteins including ZDHHC-2,7,11,15 could interact with and palmitoylate GSDME. Our findings offered new targets to achieve the transformation between chemotherapy-induced pyroptosis and apoptosis.

Bcl-2, the founding member of a family of apoptotic regulators, was initially identified as the protein product of a gene that is translocated and overexpressed in greater than 85% of follicular lymphomas (FLs). Thirty years later we now understand that Bcl-2 modulates the intrinsic apoptotic pathway by binding and neutralizing the mitochondrial permeabilizers Bax and Bak as well as a variety of pro-apoptotic proteins, including the cellular stress sensors Bim, Bid, Puma, Bad, Bmf and, under some conditions, Noxa. Despite extensive investigation of all of these proteins, important questions remain. For example, how Bax and Bak breach the outer mitochondrial membrane remains poorly understood. Likewise, how the functions of anti-apoptotic Bcl-2 family members such as eponymous Bcl-2 are affected by phosphorylation or cancer-associated mutations has been incompletely defined. Finally, whether Bcl-2 family members can be successfully targeted for therapeutic advantage is only now being investigated in the clinic. Here we review recent advances in understanding Bcl-2 family biology and biochemistry that begin to address these questions.

Understanding how some HIV-infected cells resist the cytotoxicity of HIV replication is crucial to enabling HIV cure efforts. HIV killing of CD4 T cells that replicate HIV can involve HIV protease-mediated cleavage of procaspase 8 to generate a fragment (Casp8p41) that directly binds and activates the mitochondrial proapoptotic protein BAK. Here, we demonstrate that Casp8p41 also binds with nanomolar affinity to the antiapoptotic protein Bcl-2, which sequesters Casp8p41 and prevents apoptosis. Intense activity is focused on identifying a clinical intervention that results in a long term, drug free remission of HIV-1 infection. Latently infected CD4 T cells harbor transcriptionally silent, replication-competent HIV. Because these cells persist long term and are unaffected by current therapies, the cells represent an HIV reservoir that remains undiminished by current approaches. Pilot clinical trials have tested whether reactivation of HIV-1 from latency will decrease the number of cells containing HIV DNA due to viral cytopathic effect or immune-mediated clearance. The latency reversal agents vorinostat, panobinostat, and romidepsin result in HIV reactivation, as measured by increases in cell-associated HIV RNA, but no change in cell-associated HIV DNA, indicating that the reactivating cells do not die (1-4). Multiple ongoing studies are testing augmentation of the anti-HIV immune response in combination with viral reactivation as a strategy for HIV eradication.In an effort to inform these attempts to eradicate the HIV reservoir, we and others have been examining the mechanistic basis for HIV-induced killing of CD4 T cells under different circumstances of activation and HIV replication. Although numerous pathways may contribute to the decline of uninfected CD4 T cells during uncontrolled HIV infection (5), fewer pathways have been implicated in the demise of cells directly infected by HIV. After HIV attachment, at least three distinct pathways can initiate the death of infected cells: (i) RIG-I-mediated sensing of HIV RNA (6, 7), (ii) IFI-16 sensing of unintegrated HIV DNA (8, 9), and (iii) DNA-PK-sensing of HIV integrase nicking of host DNA (10). Once integrated into host DNA, HIV can remain in a latent state

Key Points• BCL2 mutations in FL correlate with activationinduced cytidine deaminase expression and frequently alter the amino acid sequence of the protein.• Mutations in the BCL2 coding sequence at diagnosis are associated with shortened time to transformation and earlier death due to lymphoma.Follicular lymphoma (FL), an indolent neoplasm caused by a t(14;18) chromosomal translocation that juxtaposes the BCL2 gene and immunoglobulin locus, has a variable clinical course and frequently undergoes transformation to an aggressive lymphoma. Although BCL2 mutations have been previously described, their relationship to FL progression remains unclear. In this study, we evaluated the frequency and nature of BCL2 mutations in 2 independent cohorts of grade 1 and 2 FLs, along with the correlation between BCL2 mutations, transformation risk, and survival. The prevalence of BCL2 coding sequence mutations was 12% in FL at diagnosis and 53% at transformation (P < .0001). The presence of these BCL2 mutations at diagnosis correlated with an increased risk of transformation (hazard ratio 3.6; 95% CI, 2.0-6.2; P < .0001) and increased risk of death due to lymphoma (median survival of 9.5 years with BCL2 mutations vs 20.4 years without; P 5 .012).In a multivariate analysis, BCL2 mutations and high FL international prognostic index were independent risk factors for transformation and death due to lymphoma. Some mutant Bcl-2 proteins exhibited enhanced antiapoptotic capacity in vitro. Accordingly, BCL2 mutations can affect antiapoptotic Bcl-2 function, are associated with increased activationinduced cytidine deaminase expression, and correlate with increased risk of transformation and death due to lymphoma. (Blood. 2015;125(4):658-667) Introduction Follicular lymphoma (FL) has a highly variable clinical course. [1][2][3] Although some patients do well for decades, often with limited therapy, at some point 30% to 50% of patients experience histologic transformation to a more aggressive lymphoma, usually diffuse large B-cell lymphoma (DLBCL). [4][5][6][7][8][9][10][11] This transformation, which is thought to reflect the acquisition of new genetic abnormalities leading to further genomic instability, [12][13][14][15][16] has generally been associated with a poor clinical outcome. 17 Retrospective analyses from the prerituximab era have reported a median survival of only 1 to 2 years after transformation, 18,19 although a recent prospective observational study suggests somewhat better survival after transformation in the rituximab era. 20 At the present time, the FL international prognostic index (FLIPI), which integrates patient characteristics at diagnosis, is the gold standard for predicting FL clinical outcome. 21,22 There is, however, considerable interest in identifying characteristics of the FL cells themselves that might also impact prognosis. 22,23 The BCL2 gene is critical for FL pathogenesis. 24,25 Originally identified because of its translocation to the immunoglobulin heavy chain (IGH) locus as a part of the t(14;18) ...

Previous studies have suggested that the BH3 domain of the proapoptotic Bcl-2 family member Noxa only interacts with the anti-apoptotic proteins Mcl-1 and A1 but not Bcl-2. In view of the similarity of the BH3 binding domains of these anti-apoptotic proteins as well as recent evidence that studies of isolated BH3 domains can potentially underestimate the binding between full-length Bcl-2 family members, we examined the interaction of full-length human Noxa with anti-apoptotic human Bcl-2 family members. Surface plasmon resonance using bacterially expressed proteins demonstrated that Noxa binds with mean dissociation constants (K D ) of 3.4 nM for Mcl-1, 70 nM for Bcl-x L , and 250 nM for wild type human Bcl-2, demonstrating selectivity but not absolute specificity of Noxa for Mcl-1. Further analysis showed that the Noxa/Bcl-2 interaction reflected binding between the Noxa BH3 domain and the Bcl-2 BH3 binding groove. Analysis of proteins expressed in vivo demonstrated that Noxa and Bcl-2 can be pulled down together from a variety of cells. Moreover, when compared with wild type Bcl-2, certain lymphoma-derived Bcl-2 mutants bound Noxa up to 20-fold more tightly in vitro, pulled down more Noxa from cells, and protected cells against killing by transfected Noxa to a greater extent. When killing by bortezomib (an agent whose cytotoxicity in Jurkat T-cell leukemia cells is dependent on Noxa) was examined, apoptosis was enhanced by the Bcl-2/Bcl-x L antagonist ABT-737 or by Bcl-2 down-regulation and diminished by Bcl-2 overexpression. Collectively, these observations not only establish the ability of Noxa and Bcl-2 to interact but also identify Bcl-2 overexpression as a potential mechanism of bortezomib resistance.Regression of sensitive tumors such as lymphomas after effective chemotherapy is thought to reflect the induction of apoptosis (1). Chemotherapy-induced apoptosis results largely from activation of the mitochondrial or intrinsic apoptotic pathway (2, 3), which is regulated by Bcl-2 family members (4 -8). This group of proteins consists of three functionally distinct subfamilies. The multidomain proapoptotic proteins Bax and Bak oligomerize upon death stimulation to induce mitochondrial outer membrane permeabilization, thereby allowing release of cytochrome c and subsequent caspase activation. Anti-apoptotic family members, including Bcl-2, Bcl-x L , Bcl-w, Mcl-1, and A1, prevent mitochondrial outer membrane permeabilization. Conversely, BH3-only proteins 3 such as Bim, Puma, and Noxa, which share only limited sequence homology with other Bcl-2 family members in a single 15-amino acid region known as the BH3 domain (9), serve as sensors of various cellular stresses and facilitate apoptosis when activated (6, 9 -14).Although it is clear that BH3-only proteins are activated through transcriptional up-regulation or post-translational modification (7, 10), the manner in which these proteins subsequently initiate apoptosis has been controversial. Two models have emerged to explain this process (15,16). The direct a...