In vitro exploration of interactions between junctin and the Ryanodine receptor from skeletal and cardiac muscle

Muscle contraction is dependent on a large Ca2+ release from its intracellular Ca2+ store, the Sarcoplasmic Reticulum (SR), through Ryanodine receptor Ca2+ release channels (RyRs). In the resting state, striated muscle requires a tight control of Ca2+ release through RyRs. Another SR bound protein, junctin, is thought to facilitate this. Located in both skeletal and cardiac muscle, junctin has a short N-terminal domain (Njun) and bulky, highly charged C-terminal domain (Cjun), that are exposed to the cytoplasm and SR lumen respectively. Although originally thought to function as a linker between the SR calcium binding protein (calsequestrin) and RyRs, recent studies suggest the junctin may have a more complex role in regulating RyR activity and SR Ca2+ handling. In vitro studies have shown that addition of full-length junctin (FLjun) to the luminal domain of RyR directly activates RyR in lipid bilayers. However, the molecular mechanism by which junctin regulates RyR activity has been unclear. To explore the specific regions of junctin that regulate RyR, constructs corresponding to Njun, Cjun and FLjun were produced. Modified co-immunoprecipitation and affinity chromatography were employed to evaluate the direct interactions between junctin constructs and purified RyR. Both Cjun and Njun bound to the full-length RyRs. The effect of the junctin constructs on RyR1 (skeletal isoform) or RyR2 (cardiac isoform) activity was tested in lipid bilayer experiments with 1 mM luminal [Ca2+] to replicate resting conditions. As found previously, addition of FLjun to the luminal solution increased both RyR1 and RyR2 activity by ~2-3-fold. Curiously, luminal addition of Cjun strongly inhibited both RyR1 and RyR2, whereas cytoplasmic addition of Njun significantly increased RyR1 and RyR2 activity by ~5-6-fold. This was unexpected as the RyR-junctin interaction was assumed to occur only luminally. Neither luminal addition of Njun nor cytoplasmic addition of the scrambled Njun sequence altered channel activity, suggesting a specific cytoplasmic effect of Njun. This suggestion was further substantiated as cytoplasmic Njun did not change the activity of native RyRs that retained endogenous junctin. Sequential addition of Njun to the cytoplasmic solution and Cjun to the luminal solution resulted in channel activity increasing by ~2-3-fold, as observed with luminal addition of FLjun. On the other hand, the RyR inhibition induced by luminal addition of Cjun was not altered by subsequent addition of Njun to the cytoplasmic solution. The functional region of Cjun was localized to residues 85-106 that contain a KEKE motif, as luminal addition of a peptide corresponding to this region replicated the inhibitory effect of Cjun. In conclusion, the study demonstrates that junctin regulates RyR1 and RyR2 via interactions in both the cytoplasm and SR lumen, the combined actions of Njun and Cjun indicate that the novel cytoplasmic Njun-RyR interaction must be established before the luminal Cjun-RyR interaction to replicate the FLjun modulation of RyR1 and RyR2 activity

An analysis of 1256 cases of sporadic ruptured cerebral aneurysm in a single Chinese institution

Background: To review the epidemiology of sporadic ruptured cerebral aneurysm. Methods: This is a retrospective study of consecutive 1256 Chinese patients between January 2006 and January 2013, who were admitted to the Second Hospital of Hebei Medical University, China, for spontaneous subarachnoid hemorrhage due to a rupture of cerebral artery aneurysm. In 288 males and 478 females, the size of aneurysms was measured by a neuroradiologist on DSA. In 123 males and 184 females, the size of the ruptured aneurysms was not measured. The remaining patients, with 61 males and 122 females, had multiple aneurysms, and the medical record could not reliably determine the specific aneurysm responsible for the rupture. Results: In total there were 784 females and 472 males with a female/male ratio of 1.66. The female/male ratio was down to 0.50 for patients younger than 35 yrs. For both males and females, aneurysm rupture was most common during the age of 50-59 yrs. Ruptured aneurysms were mostly of 2 mm-5 mm in size (47.1%), followed by 5 mm-10 mm (39.7%). Ruptured single cerebral aneurysm occurred in anterior circulation in 95.0% of the cases, with 5.0% occurred in posterior circulation. Ruptured aneurysm most commonly occurred at posterior communicating artery (34.9%) and anterior communicating artery (29.5%). 183 cases (14.6%) had multiple aneurysms. Conclusions: With younger patients, there is a male predominance in our series. Ninety percent of patients have ruptured aneurysms less than 10 mm in size. © 2014 Zhao et al.published_or_final_versio

The candidate tumor suppressor gene ECRG4 inhibits cancer cells migration and invasion in esophageal carcinoma

<p>Abstract</p> <p>Background</p> <p>The esophageal cancer related gene 4 (ECRG4) was initially identified and cloned in our laboratory from human normal esophageal epithelium (GenBank accession no.<ext-link ext-link-id="AF325503" ext-link-type="gen">AF325503</ext-link>). ECRG4 was a new tumor suppressor gene in esophageal squamous cell carcinoma (ESCC) associated with prognosis. In this study, we investigated the novel tumor-suppressing function of ECRG4 in cancer cell migration, invasion, adhesion and cell cycle regulation in ESCC.</p> <p>Methods</p> <p>Transwell and Boyden chamber experiments were utilized to examined the effects of ECRG4 expression on ESCC cells migration, invasion and adhesion. And flow cytometric analysis was used to observe the impact of ECRG4 expression on cell cycle regulation. Finally, the expression levels of cell cycle regulating proteins p53 and p21 in human ESCC cells transfected with ECRG4 gene were evaluated by Western blotting.</p> <p>Results</p> <p>The restoration of ECRG4 expression in ESCC cells inhibited cancer cells migration and invasion (<it>P </it>< 0.05), which did not affect cell adhesion capacity (<it>P </it>> 0.05). Furthermore, ECRG4 could cause cell cycle G1 phase arrest in ESCC (<it>P </it>< 0.05), through inducing the increased expression of p53 and p21 proteins.</p> <p>Conclusion</p> <p>ECRG4 is a candidate tumor suppressor gene which suppressed tumor cells migration and invasion without affecting cell adhesion ability in ESCC. Furthermore, ECRG4 might cause cell cycle G1 phase block possibly through inducing the increased expression of p53 and p21 proteins in ESCC.</p

Distributionally Robust Optimization and Invariant Representation Learning for Addressing Subgroup Underrepresentation: Mechanisms and Limitations

Spurious correlation caused by subgroup underrepresentation has received increasing attention as a source of bias that can be perpetuated by deep neural networks (DNNs). Distributionally robust optimization has shown success in addressing this bias, although the underlying working mechanism mostly relies on upweighting under-performing samples as surrogates for those underrepresented in data. At the same time, while invariant representation learning has been a powerful choice for removing nuisance-sensitive features, it has been little considered in settings where spurious correlations are caused by significant underrepresentation of subgroups. In this paper, we take the first step to better understand and improve the mechanisms for debiasing spurious correlation due to subgroup underrepresentation in medical image classification. Through a comprehensive evaluation study, we first show that 1) generalized reweighting of under-performing samples can be problematic when bias is not the only cause for poor performance, while 2) naive invariant representation learning suffers from spurious correlations itself. We then present a novel approach that leverages robust optimization to facilitate the learning of invariant representations at the presence of spurious correlations. Finetuned classifiers utilizing such representation demonstrated improved abilities to reduce subgroup performance disparity, while maintaining high average and worst-group performance.Comment: Accepted at FAIMI-202

Poly[[bis­(μ2-6-methyl­pyrazin-2-carboxyl­ato-κ3 N 1,O:N 4)copper(II)] dihydrate]

In the title compound, {[Cu(C6H5N2O2)2]·2H2O}n, the CuII ion (site symmetry ) is coordinated by two N,O-bidentate ligands and two N-monodentate ligands in a distorted CuO2N4 octa­hedral geometry. Each anion acts as a bridge between two cations, thus forming a two-dimensional polymeric network parallel to the ab plane. The packing is consolidated by O—H⋯O hydrogen bonds. One of the O atoms of the ligand and both water mol­ecules are disordered

Life-cycle GHG emission Factors of Final Energy in China

AbstractIn this manuscript, a model for the estimation of the life-cycle GHG emission factors of final energy and an empirical study of China is presented. A linear programming method is utilized to solve the problem that several forms of final energy are utilized in the life-cycle of one certain type of final energy. Nine types of final energy are considered, including raw coal, crude oil, raw natural gas, treated coal, diesel, gasoline, fuel oil, treated natural gas, and electricity. The results indicate that the life-cycle GHG emission factors of final energy in China slightly decreased in recent years