The Role of Modified UNC-68 in Age-related Caenorhabditis elegans Muscle Function Loss

Age-dependent loss of body wall muscle function and locomotion has been observed in C. elegans, however its cause has yet to be elucidated. Utilizing biochemical techniques and calcium imaging, we demonstrate that aberrant calcium (Ca2+) release via the ryanodine receptor (RyR) homologue UNC-68 contributes to age-dependent muscle weakness in C. elegans. We show that UNC-68 comprises a macromolecular complex bearing FKB-2, a C. elegans immunophilin with high homology to the stabilizing subunit calstabin (calcium channel stabilizing binding protein, or FKBP12). Furthermore, we demonstrate that as the nematode ages, UNC-68 is oxidized and depleted of FKB-2, resulting in “leaky” channels, depleted SR calcium stores, and a reduction in body wall muscle Ca2+ transients at baseline. These perturbations resulted in a motility phenotype, where fkb-2(ok3007) worms harboring a deletion mutation that abolishes FKB-2 binding to the UNC-68 macromolecular complex suffered from poor muscle performance and exercise fatigue in swimming trials. Moreover, pharmacological interventions inducing oxidization of UNC-68 and depletion FKB-2 from the channel independently cause reduced body wall muscle Ca2+ transients, strongly suggesting that UNC-68 oxidation and FKB-2 depletion contribute to muscle function loss observed in aging. UNC-68 oxidation was found to correlate with lifespan, happening earlier in short-lived mitochondrial electron transport chain strains and later in long-lived worms. Finally, preventing FKB-2 depletion from the UNC-68 macromolecular complex in aged C. elegans using the Rycal drug S107 improved muscle Ca2+ transients. Taken together, our data implicate UNC-68 dysfunction in the underlying mechanism of muscle function loss in C. elegans, analogous to observations made of RyR1 dysfunction in aged mammalian skeletal muscle, and describes for the first time a potential role for FKB-2 in C.elegans physiology

Cyclin F-Mediated Degradation of Ribonucleotide Reductase M2 Controls Genome Integrity and DNA Repair

F-box proteins are the substrate binding subunits of SCF (Skp1-Cul1-F-box protein) ubiquitin ligase complexes. Using affinity purifications and mass spectrometry, we identified RRM2 (the ribonucleotide reductase family member 2) as an interactor of the F-box protein cyclin F. Ribonucleotide reductase (RNR) catalyzes the conversion of ribonucleotides to deoxyribonucleotides (dNTPs), which are necessary for both replicative and repair DNA synthesis. We found that, during G2, following CDK-mediated phosphorylation of Thr33, RRM2 is degraded via SCFcyclin F to maintain balanced dNTP pools and genome stability. After DNA damage, cyclin F is downregulated in an ATR-dependent manner to allow accumulation of RRM2. Defective elimination of cyclin F delays DNA repair and sensitizes cells to DNA damage, a phenotype that is reverted by expressing a nondegradable RRM2 mutant. In summary, we have identified a biochemical pathway that controls the abundance of dNTPs and ensures efficient DNA repair in response to genotoxic stress

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

Causal effect of plasminogen activator inhibitor type 1 on coronary heart disease

Background--Plasminogen activator inhibitor type 1 (PAI-1) plays an essential role in the fibrinolysis system and thrombosis. Population studies have reported that blood PAI-1 levels are associated with increased risk of coronary heart disease (CHD). However, it is unclear whether the association reflects a causal influence of PAI-1 on CHD risk. Methods and Results--To evaluate the association between PAI-1 and CHD, we applied a 3-step strategy. First, we investigated the observational association between PAI-1 and CHD incidence using a systematic review based on a literature search for PAI-1 and CHD studies. Second, we explored the causal association between PAI-1 and CHD using a Mendelian randomization approach using summary statistics from large genome-wide association studies. Finally, we explored the causal effect of PAI-1 on cardiovascular risk factors including metabolic and subclinical atherosclerosis measures. In the systematic meta-analysis, the highest quantile of blood PAI-1 level was associated with higher CHD risk comparing with the lowest quantile (odds ratio=2.17; 95% CI: 1.53, 3.07) in an age- and sex-adjusted model. The effect size was reduced in studies using a multivariable-adjusted model (odds ratio=1.46; 95% CI: 1.13, 1.88). The Mendelian randomization analyses suggested a causal effect of increased PAI-1 level on CHD risk (odds ratio=1.22 per unit increase of log-transformed PAI-1; 95% CI: 1.01, 1.47). In addition, we also detected a causal effect of PAI-1 on elevating blood glucose and high-density lipoprotein cholesterol. Conclusions--Our study indicates a causal effect of elevated PAI-1 level on CHD risk, which may be mediated by glucose dysfunction