In stressed cells, apoptosis ensues when Bcl-2 family members Bax or Bak oligomerize and permeabilize the mitochondrial outer membrane. Certain BH3-only relatives can directly activate them to ...mediate this pivotal, poorly understood step. To clarify the conformational changes that induce Bax oligomerization, we determined crystal structures of BaxΔC21 treated with detergents and BH3 peptides. The peptides bound the Bax canonical surface groove but, unlike their complexes with prosurvival relatives, dissociated Bax into two domains. The structures define the sequence signature of activator BH3 domains and reveal how they can activate Bax via its groove by favoring release of its BH3 domain. Furthermore, Bax helices α2–α5 alone adopted a symmetric homodimer structure, supporting the proposal that two Bax molecules insert their BH3 domain into each other’s surface groove to nucleate oligomerization. A planar lipophilic surface on this homodimer may engage the membrane. Our results thus define critical Bax transitions toward apoptosis.
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► Activator BH3 domains bind the Bax canonical groove and help free the Bax BH3 ► Bax:BH3 peptide complexes reveal sequence characteristics of activator BH3 domains ► Bax activation separates its “core” domain (helices α1–α5) and “latch” (α6–α8) ► The freed core forms a symmetric BH3-in-groove dimer with a lipophilic surface
The structural transitions that set proapoptotic Bax on the pathway to forming a pore in the outer mitochondrial membrane are revealed in crystal structures of Bax bound to activator BH3 peptides.
BCL-2 family antagonists for cancer therapy Lessene, Guillaume; Czabotar, Peter E; Colman, Peter M
Nature reviews. Drug discovery,
12/2008, Volume:
7, Issue:
12
Journal Article
Peer reviewed
Overexpression of members of the BCL-2 family of pro-survival proteins is commonly associated with unfavourable pathogenesis in cancer. The convergence of cytotoxic stress signals on the extended ...BCL-2 protein family provides the biological rationale for directly targeting this family to induce apoptotic cell death. Recently, several compounds have been described that inhibit the interaction between BCL-2 family members and their natural ligand, a helical peptide sequence known as the BH3 domain. Here, we review preclinical and clinical data on these compounds, and recommend four criteria that define antagonists of the BCL-2 protein family.
Apoptotic stimuli activate and oligomerize the proapoptotic proteins Bak and Bax, resulting in mitochondrial outer-membrane permeabilization and subsequent cell death. This activation can occur when ...certain BH3-only proteins interact directly with Bak and Bax. Recently published crystal structures reveal that Bax separates into core and latch domains in response to BH3 peptides. The distinguishing characteristics of BH3 peptides capable of directly activating Bax were also elucidated. Here we identify specific BH3 peptides capable of “unlatching” Bak and describe structural insights into Bak activation and oligomerization. Crystal structures and crosslinking experiments demonstrate that Bak undergoes a conformational change similar to that of Bax upon activation. A structure of the Bak core domain dimer provides a high-resolution image of this key intermediate in the pore-forming oligomer. Our results confirm an analogous mechanism for activation and dimerization of Bak and Bax in response to certain BH3 peptides.
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•Bak separates into core and latch subdomains upon activation•Core/latch separation is required for Bak-mediated mitochondrial permeabilization•The freed core subdomain forms BH3:groove symmetric dimers•BH3:groove dimers possess a lipophilic surface that may engage membranes
BH3-only proteins activate the proapoptotic protein Bak, resulting in its oligomerization and disruption of the mitochondrial outer membrane. Here, Brouwer et al. show that Bak separates into core and latch domains upon activation. Released core domains form BH3:groove dimers, the likely building block for the larger Bak oligomer.
Venetoclax is a first-in-class cancer therapy that interacts with the cellular apoptotic machinery promoting apoptosis. Treatment of patients suffering chronic lymphocytic leukaemia with this BCL-2 ...antagonist has revealed emergence of a drug-selected BCL-2 mutation (G101V) in some patients failing therapy. To understand the molecular basis of this acquired resistance we describe the crystal structures of venetoclax bound to both BCL-2 and the G101V mutant. The pose of venetoclax in its binding site on BCL-2 reveals small but unexpected differences as compared to published structures of complexes with venetoclax analogues. The G101V mutant complex structure and mutant binding assays reveal that resistance is acquired by a knock-on effect of V101 on an adjacent residue, E152, with venetoclax binding restored by a E152A mutation. This provides a framework for considering analogues of venetoclax that might be effective in combating this mutation.
To assess the efficacy and safety of closed-loop insulin delivery compared with sensor-augmented pump therapy among older adults with type 1 diabetes.
This open-label, randomized (1:1), crossover ...trial compared 4 months of closed-loop versus sensor-augmented pump therapy. Eligible adults were aged ≥60 years, with type 1 diabetes (duration ≥10 years), using an insulin pump. The primary outcome was continuous glucose monitoring (CGM) time in range (TIR; 3.9-10.0 mmol/L).
There were 30 participants (mean age 67 SD 5 years), with median type 1 diabetes duration of 38 years (interquartile range IQR 20-47), randomized (n = 15 to each sequence); all completed the trial. The mean TIR was 75.2% (SD 6.3) during the closed-loop stage and 69.0% (9.1) during the sensor-augmented pump stage (difference of 6.2 percentage points 95% CI 4.4 to 8.0; P < 0.0001). All prespecified CGM metrics favored closed loop over the sensor-augmented pump; benefits were greatest overnight. Closed loop reduced CGM time <3.9 mmol/L during 24 h/day by 0.5 percentage points (95% CI 0.3 to 1.1; P = 0.0005) and overnight by 0.8 percentage points (0.4 to 1.1; P < 0.0001) compared with sensor-augmented pump. There was no significant difference in HbA1c between closed-loop versus sensor-augmented pump stages (7.3% IQR, 7.1-7.5 (56 mmol/mol 54-59) vs. 7.5% 7.1-7.9 (59 mmol/mol 54-62), respectively; P = 0.13). Three severe hypoglycemia events occurred during the closed-loop stage and two occurred during the sensor-augmented pump stage; no hypoglycemic events required hospitalization. One episode of diabetic ketoacidosis occurred during the sensor-augmented pump stage; no serious adverse events occurred during the closed-loop stage.
Closed-loop therapy is an effective treatment option for older adults with long-duration type 1 diabetes, and no safety issues were identified. These older adults had higher TIR accompanied by less time below range during closed loop than during sensor-augmented pump therapy. Of particular clinical importance, closed loop reduced the time spent in hypoglycemic range overnight.
To investigate whether liraglutide added to treat-to-target insulin improves glycemic control and reduces insulin requirements and body weight in subjects with type 1 diabetes.
A 52-week, ...double-blind, treat-to-target trial involving 1,398 adults randomized 3:1 to receive once-daily subcutaneous injections of liraglutide (1.8, 1.2, or 0.6 mg) or placebo added to insulin.
HbA1c level was reduced 0.34-0.54% (3.7-5.9 mmol/mol) from a mean baseline of 8.2% (66 mmol/mol), and significantly more for liraglutide 1.8 and 1.2 mg compared with placebo (estimated treatment differences ETDs: 1.8 mg liraglutide -0.20% 95% CI -0.32; -0.07; 1.2 mg liraglutide -0.15% 95% CI -0.27; -0.03; 0.6 mg liraglutide -0.09% 95% CI -0.21; 0.03). Insulin doses were reduced by the addition of liraglutide 1.8 and 1.2 mg versus placebo (estimated treatment ratios: 1.8 mg liraglutide 0.92 95% CI 0.88; 0.96; 1.2 mg liraglutide 0.95 95% CI 0.91; 0.99; 0.6 mg liraglutide 1.00 95% CI 0.96; 1.04). Mean body weight was significantly reduced in all liraglutide groups compared with placebo ETDs (1.8 mg liraglutide -4.9 kg 95% CI -5.7; -4.2; 1.2 mg liraglutide -3.6 kg 95% CI -4.3; -2.8; 0.6 mg liraglutide -2.2 kg 95% CI -2.9; -1.5). The rate of symptomatic hypoglycemia increased in all liraglutide groups (estimated rate ratios: 1.8 mg liraglutide 1.31 95% CI 1.07; 1.59; 1.2 mg liraglutide 1.27 95% CI 1.03; 1.55; 0.6 mg liraglutide 1.17 95% CI 0.97; 1.43), and hyperglycemia with ketosis increased significantly for liraglutide 1.8 mg only (event rate ratio 2.22 95% CI 1.13; 4.34).
Liraglutide added to insulin therapy reduced HbA1c levels, total insulin dose, and body weight in a population that was generally representative of subjects with type 1 diabetes, accompanied by increased rates of symptomatic hypoglycemia and hyperglycemia with ketosis, thereby limiting clinical use in this group.
ObjectivesSystemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease associated with diffuse immune cell dysfunction. CD40–CD40 ligand (CD40L) interaction activates B cells, ...antigen-presenting cells and platelets. CD40L blockade might provide an innovative treatment for systemic autoimmune disorders. We investigated the safety and clinical activity of dapirolizumab pegol, a polyethylene glycol conjugated anti-CD40L Fab' fragment, in patients with SLE.MethodsThis 32-week randomised, double-blind, multicentre study (NCT01764594) evaluated repeated intravenous administration of dapirolizumab pegol in patients with SLE who were positive for/had history of antidouble stranded DNA/antinuclear antibodies and were on stable doses of immunomodulatory therapies (if applicable). Sixteen patients were randomised to 30 mg/kg dapirolizumab pegol followed by 15 mg/kg every 2 weeks for 10 weeks; eight patients received a matched placebo regimen. Randomisation was stratified by evidence of antiphospholipid antibodies. Patients were followed for 18 weeks after the final dose.ResultsNo serious treatment-emergent adverse events, thromboembolic events or deaths occurred. Adverse events were mild or moderate, transient and resolved without intervention. One patient withdrew due to infection.Efficacy assessments were conducted only in patients with high disease activity at baseline. Five of 11 (46%) dapirolizumab pegol-treated patients achieved British Isles Lupus Assessment Group-based Composite Lupus Assessment response (vs 1/7; 14% placebo) and 5/12 (42%) evaluable for SLE Responder Index-4 responded by week 12 (vs 1/7; 14% placebo). Mechanism-related gene expression changes were observed in blood RNA samples.ConclusionsDapirolizumab pegol could be an effective biological treatment for SLE. Further studies are required to address efficacy and safety.Trial registration numberNCT01764594.
Progress in the discovery of new antiviral medicines is tempered by the rapidity with which drug-resistant variants emerge. A review of the resistance-suppressing properties of four classes of ...antivirals is presented: influenza virus neuraminidase inhibitors, HIV protease inhibitors, antibodies, and protein-based fusion inhibitors. The analysis supports the hypothesis that the more similar the drug is to the target's natural ligands, the higher the barrier to resistance. However, other factors, such as entropy compensation and solvent anchoring, might also be exploited for improved drug design.
Epstein-Barr virus (EBV) is associated with human malignancies, especially those affecting the B cell compartment such as Burkitt lymphoma. The virally encoded homolog of the mammalian pro-survival ...protein Bcl-2, BHRF1 contributes to viral infectivity and lymphomagenesis. In addition to the pro-apoptotic BH3-only protein Bim, its key target in lymphoid cells, BHRF1 also binds a selective sub-set of pro-apoptotic proteins (Bid, Puma, Bak) expressed by host cells. A consequence of BHRF1 expression is marked resistance to a range of cytotoxic agents and in particular, we show that its expression renders a mouse model of Burkitt lymphoma untreatable. As current small organic antagonists of Bcl-2 do not target BHRF1, the structures of it in complex with Bim or Bak shown here will be useful to guide efforts to target BHRF1 in EBV-associated malignancies, which are usually associated with poor clinical outcomes.
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