The Spo13/Meikin pathway confines the onset of gamete differentiation to meiosis II in yeast.

Sexual reproduction requires genome haploidization by the two divisions of meiosis and a differentiation program to generate gametes. Here, we have investigated how sporulation, the yeast equivalent of gamete differentiation, is coordinated with progression through meiosis. Spore differentiation is initiated at metaphase II when a membrane-nucleating structure, called the meiotic plaque, is assembled at the centrosome. While all components of this structure accumulate already at entry into meiosis I, they cannot assemble because centrosomes are occupied by Spc72, the receptor of the γ-tubulin complex. Spc72 is removed from centrosomes by a pathway that depends on the polo-like kinase Cdc5 and the meiosis-specific kinase Ime2, which is unleashed by the degradation of Spo13/Meikin upon activation of the anaphase-promoting complex at anaphase I. Meiotic plaques are finally assembled upon reactivation of Cdk1 at entry into metaphase II. This unblocking-activation mechanism ensures that only single-copy genomes are packaged into spores and might serve as a paradigm for the regulation of other meiosis II-specific processes.

Oxeiptosis, a ROS-induced caspase-independent apoptosis-like cell-death pathway.

Reactive oxygen species (ROS) are generated by virus-infected cells; however, the physiological importance of ROS generated under these conditions is unclear. Here we found that the inflammation and cell death induced by exposure of mice or cells to sources of ROS were not altered in the absence of canonical ROS-sensing pathways or known cell-death pathways. ROS-induced cell-death signaling involved interactions among the cellular ROS sensor and antioxidant factor KEAP1, the phosphatase PGAM5 and the proapoptotic factor AIFM1. Pgam5 -/- mice showed exacerbated lung inflammation and proinflammatory cytokines in an ozone-exposure model. Similarly, challenge with influenza A virus led to increased infiltration of the virus, lymphocytic bronchiolitis and reduced survival of Pgam5 -/- mice. This pathway, which we have called 'oxeiptosis', was a ROS-sensitive, caspase independent, non-inflammatory cell-death pathway and was important for protection against inflammation induced by ROS or ROS-generating agents such as viral pathogens.

The efficacy of hydrotalcite compared with OTC famotidine in the on-demand treatment of gastroesophageal reflux disease: a non-inferiority trial.

BACKGROUND: Antacids and gastric acid inhibitors are effective in the self-treatment of gastroesophageal reflux disease (GERD). The aim was to investigate onset of action of the antacid hydrotalcite compared with the OTC H2-receptor antagonist famotidine in patients suffering from heartburn. MATERIAL/METHODS: A total of 53 patients with endoscopically diagnosed GERD grade 0-1 took part in this open, randomized, parallel-group comparison trial: 26 patients received a single dose of 1000 mg hydrotalcite and 27 patients a single dose of 10 mg famotidine on the occasion of a symptomatic reflux episode. Severity of heartburn and accompanying symptoms were documented on a four-point verbal rating scale (VRS) at baseline and up to four hours after intake. Onset and duration of action were defined by the number of patients experiencing improvement of heartburn from severe or moderate to mild or none compared with baseline. RESULTS: Hydrotalcite was significantly superior (p<0.001) to famotidine in increasing the proportion of responders within the first 45 minutes, starting 10 minutes after drug intake. Between 60 and 120 minutes, both compounds showed equal efficacy. Three hours after intake the response rate was 90.9% for hydrotalcite and 92.0% for famotidine. After four hours the response rates were 86.4% for hydrotalcite and 96.0% for famotidine. In both groups, no adverse events were observed. CONCLUSIONS: The results indicate that hydrotalcite relieves the symptoms of gastroesophageal reflux faster than OTC famotidine and is equally effective for up to two hours. It is a safe and effective self-medication for on-demand treatment of heartburn.

Distribution of HCN1 and HCN2 in rat auditory brainstem nuclei.

Auditory brainstem neurons that are involved in the precise analysis of the temporal pattern of sounds have ionic currents activated near the resting potential to shorten membrane time constants. One of these currents is the hyperpolarization-activated current (Ih). Molecular cloning of the channels underlying Ih revealed four different isoforms (HCN1-4). HCN1 and HCN2, which are widely distributed in the brain, differ in their activation kinetics, voltage dependence and sensitivity to cAMP. We determined the distribution of the HCN1 and HCN2 isoform in the auditory brainstem and midbrain of young rats (P20-30), using standard immunohistochemical techniques. HCN1 antibodies gave rise to punctate staining on the somatic and dendritic membrane. Strong HCN1 staining was present on octopus and bushy cells of the ventral cochlear nucleus, principal neurons of the lateral and medial superior olive, and neurons of the ventral nucleus of the lateral lemniscus. No HCN1 staining was observed in the dorsal cochlear nucleus and the medial nucleus of the trapezoid body (MNTB). In contrast, HCN2 staining was strongest in the MNTB and the dorsal nucleus of the lateral lemniscus. Strong HCN2 antibody labelling was also observed in bushy cells of the ventral cochlear nucleus. In the central nucleus of the inferior colliculus only a subpopulation of neurons showed HCN1 or HCN2 immunolabelling. This differential distribution of HCN1 and HCN2 channels is in agreement with the physiologically observed Ih currents in corresponding neuronal populations and might represent the basis for functional heterogeneity and diverse sensitivity to neuromodulators.

Flexibility analysis and structure comparison of two crystal forms of calcium-free human m-calpain.

The calpains form a growing family of structurally related intracellular multidomain cysteine proteinases containing a papain-related catalytic domain, whose activity depends on calcium. The calpains are believed to play important roles in cytoskelatel remodeling processes, cell differentiation, apoptosis and signal transduction, but are also implicated in a number of diseases. Recent crystal structures of truncated rat and full-length human apo-m-calpain revealed the domain arrangement and explained the inactivity of m-calpain in the absence of calcium by a disrupted catalytic domain. Proteolysis studies have indicated several susceptible sites, in particular in the catalytic subdomain IIb and in the following domain III, which are more accessible to attacking proteinases in the presence than in the absence of calcium. The current view is that m-calpain exhibits a number of calcium binding sites, which upon calcium binding cooperatively interact, triggering the reformation of a papain-like catalytic domain, accompanied by enhanced mobilisation of the whole structure. To further analyse the flexibility of m-calpain, we have determined and refined the human full-length apo-m-calpain structure of a second crystal form to 3.15 A resolution. Here we present this new structure, compare it with our first structure now re-refined with tighter constrain parameters, discuss the flexibility in context with the proteolysis and calcium binding data available, and suggest implications for the calcium-induced activation process.