Structural basis and regulation of the reductive stress response.

Although oxidative phosphorylation is best known for producing ATP, it also yields reactive oxygen species (ROS) as invariant byproducts. Depletion of ROS below their physiological levels, a phenomenon known as reductive stress, impedes cellular signaling and has been linked to cancer, diabetes, and cardiomyopathy. Cells alleviate reductive stress by ubiquitylating and degrading the mitochondrial gatekeeper FNIP1, yet it is unknown how the responsible E3 ligase CUL2FEM1B can bind its target based on redox state and how this is adjusted to changing cellular environments. Here, we show that CUL2FEM1B relies on zinc as a molecular glue to selectively recruit reduced FNIP1 during reductive stress. FNIP1 ubiquitylation is gated by pseudosubstrate inhibitors of the BEX family, which prevent premature FNIP1 degradation to protect cells from unwarranted ROS accumulation. FEM1B gain-of-function mutation and BEX deletion elicit similar developmental syndromes, showing that the zinc-dependent reductive stress response must be tightly regulated to maintain cellular and organismal homeostasis.

A Cellular Mechanism to Detect and Alleviate Reductive Stress.

Metazoan organisms rely on conserved stress response pathways to alleviate adverse conditions and preserve cellular integrity. Stress responses are particularly important in stem cells that provide lifetime support for tissue formation and repair, but how these protective systems are integrated into developmental programs is poorly understood. Here we used myoblast differentiation to identify the E3 ligase CUL2FEM1B and its substrate FNIP1 as core components of the reductive stress response. Reductive stress, as caused by prolonged antioxidant signaling or mitochondrial inactivity, reverts the oxidation of invariant Cys residues in FNIP1 and allows CUL2FEM1B to recognize its target. The ensuing proteasomal degradation of FNIP1 restores mitochondrial activity to preserve redox homeostasis and stem cell integrity. The reductive stress response is therefore built around a ubiquitin-dependent rheostat that tunes mitochondrial activity to redox needs and implicates metabolic control in coordination of stress and developmental signaling.

Long-term outcomes of repeat vs initial trabeculectomy in open-angle glaucoma.

PURPOSE: To evaluate the long-term intraocular pressure (IOP) control and to identify risk factors for failure of repeat trabeculectomy with mitomycin C (MMC) in patients with open-angle glaucoma. DESIGN: Retrospective case-control study. METHODS: Seventy-five eyes (67 patients) that had undergone repeat trabeculectomy with MMC were matched to 75 eyes (64 patients) that had undergone initial trabeculectomy with MMC according to age, gender, race, diagnosis, preoperative IOP, number of glaucoma medications, and lens status in an institutional setting. Surgical successes were defined as: 1) IOP < or =18 mm Hg and > or = 20% reduction in IOP, 2) < or = 15 mm Hg IOP and > or = 25% reduction in IOP, and 3) < or = 12 mm Hg IOP and > or = 30% reduction in IOP from baseline, with or without glaucoma medications, and were assessed by Kaplan-Meier survival analyses. Risk factors for failure in the repeat trabeculectomy group were analyzed by the Cox proportional hazard regression model. The main outcome measures were success rate, number of medications, and visual acuity. RESULTS: Eyes that underwent initial trabeculectomy with MMC had a statistically significantly higher cumulative surgical success rate than those that underwent repeat trabeculectomy with MMC at 3 years according to criteria B (61.3% vs 41.3%; P = .022) and C (52.0% vs 32.0%; P = .021). In eyes that underwent repeat trabeculectomy, younger age and requirement of laser suture lysis were significant risk factors for surgical failure. Eyes that underwent initial trabeculectomy required a statistically fewer number of medications than eyes that underwent repeat trabeculectomy (0.6 vs 1.2; P = .013). CONCLUSIONS: Repeat trabeculectomy with MMC is less successful at achieving IOP reduction in open-angle glaucoma than is initial trabeculectomy with MMC at 3 years or more.

Clinical trial participation among patients enrolled in the Glioma Outcomes Project.

BACKGROUND: Patient participation in well-designed and conducted clinical trials enables researchers to test new therapies. An understanding of the variables that possibly influence patient enrollment may help in patient recruitment for future trials. The authors evaluated factors that influenced patient enrollment in clinical trials using a prospective, large, multi-institutional registry of patients with malignant glioma. METHODS: Data were examined from 708 patients who underwent first or second surgery for a malignant glioma who were enrolled in the Glioma Outcomes Project, which is a prospective observational data base that captures clinical practice patterns. The frequency of clinical trial participation and the variables that may have been associated with trial participation were evaluated. These variables included age, gender, race, household income, educational level, first versus second craniotomy, histology, and whether the patient was treated at an academic institution. RESULTS: One hundred fifty-one of 708 patients (21.3%) participated in a clinical trial, which was higher than the participation reported typically for patients with other types of primary malignancies. In univariate analysis, race, histology, and first craniotomy were significant between the two groups, with Caucasian patients and patients with glioblastoma histology showing higher participation rates. In a multivariate logistic regression model, significant predictors included young age and glioblastoma multiforme histology. CONCLUSIONS: The authors present information on factors that may influence clinical trial participation among patients with malignant glioma and compare their data with information described previously on patients with other types of malignant disease. The percent of participation among the patients in the current study was greater than among patients with other primary tumor sites. Strategies should be implemented to improve recruitment to neuro-oncology trials, especially in elderly and minority populations.