The Role of Extramembranous Cytoplasmic Termini in Assembly and Stability of the Tetrameric K+-Channel KcsA

Membrane-active alcohol 2,2,2-trifluoroethanol has been proven to be an attractive tool in the investigation of the intrinsic stability of integral membrane protein complexes by taking K+-channel KcsA as a suitable and representative ion channel. In the present study, the roles of both cytoplasmic N and C termini in channel assembly and stability of KcsA were determined. The N terminus (1–18 residues) slightly increased tetramer stability via electrostatic interactions in the presence of 30 mol.% acidic phosphatidylglycerol (PG) in phosphatidylcholine lipid bilayer. Furthermore, the N terminus was found to be potentially required for efficient channel (re)assembly. In contrast, truncation of the C terminus (125–160 residues) greatly facilitated channel reversibility from either a partially or a completely unfolded state, and this domain was substantially involved in stabilizing the tetramer in either the presence or absence of PG in lipid bilayer. These studies provide new insights into how extramembranous parts play their crucial roles in the assembly and stability of integral membrane protein complexes

MscS-like mechanosensitive channels in plants and microbes

The challenge of osmotic stress is something all living organisms must face as a result of environmental dynamics. Over the past three decades, innovative research and cooperation across disciplines have irrefutably established that cells utilize mechanically gated ion channels to release osmolytes and prevent cell lysis during hypoosmotic stress. Early electrophysiological analysis of the inner membrane of Escherichia coli identified the presence of three distinct mechanosensitive activities. The subsequent discoveries of the genes responsible for two of these activities, the mechanosensitive channels of large (MscL) and small (MscS) conductance, led to the identification of two diverse families of mechanosensitive channels. The latter of these two families, the MscS family, consists of members from bacteria, archaea, fungi, and plants. Genetic and electrophysiological analysis of these family members has provided insight into how organisms use mechanosensitive channels for osmotic regulation in response to changing environmental and developmental circumstances. Furthermore, determining the crystal structure of E. coli MscS and several homologues in several conformational states has contributed to our understanding of the gating mechanisms of these channels. Here we summarize our current knowledge of MscS homologues from all three domains of life and address their structure, proposed physiological functions, electrophysiological behaviors, and topological diversity

IgG4-Related Diseases and the Liver

IgG4-related disease (IgG4-RD) is a systemic illness including autoimmune pancreatitis and IgG4-related sclerosing cholangitis (IgG4-SC). Although hepatic presentation of IgG4-RD has been reported, whether intrahepatic small bile ducts and hepatocytes are direct targets of IgG4-RD is uncertain. IgG4-RD is pathologically characterized by the numerous IgG4+ cells found in affected organs, but this IgG4 positivity is also frequently found in extrahepatic cholangiocarcinoma and is prominent, albeit rarely, in other hepatobiliary diseases including primary sclerosing cholangitis and autoimmune hepatitis. Moreover, cholangiocarcinoma arising from precedent IgG4-SC and IgG4-SC accompanying precursor lesions of cholangiocarcinoma (biliary intraepithelial neoplasia) are also reported. Diagnostic criteria for IgG-RD and IgG4-SC were recently proposed, but each individual case should be diagnosed clinicopathologically on the basis of its individual features. © Springer Japan 2016.[Book Chapter

Validation study of the Japanese version of MD Anderson Symptom Inventory for Brain Tumor module

Abstract Objective The MD Anderson Symptom Inventory for Brain Tumor (MDASI-BT) module is a widely used instrument for measuring symptom burden and interference of daily activities in brain tumor patients. This study aims to develop and validate its Japanese version (MDASI-BT-Japanese). Methods Following forward and backward translation of the original MDASI-BT into Japanese, understandability and feasibility were assessed by cognitive debriefing. Subsequently, patients with brain tumors were asked to fill out MDASI-BT-Japanese and European Quality of Life-5 Dimensions (EQ-5D). Feasibility, reliability and validity of MDASI-BT-Japanese were assessed. Results Cognitive debriefing confirmed overall ease of completion and good understandability. The study population composed of 140 patients with brain tumors (most commonly gliomas). The mean symptom severity score and mean interference score were 1.9 ± 1.7 and 2.8 ± 2.7, respectively. The top items included distress and drowsiness for symptom severity and general activity and work for interference. The median time required was 4 minutes (range, 0.5–30), and missing values were seen in 1%. Internal consistency was proven by excellent Cronbach’s coefficient alpha (0.94 for symptom severity, 0.92 for interference). Test–retest reliability was assessed with acceptable intra-class correlation coefficient (mean, 0.76). Correlation efficient ranged between 0.7 and 0.9 for convergent validity. Known-group validity was confirmed by significantly different mean symptom severity score and mean interference score among patients with different performance status. As evidence of concurrent validity, MDASI-BT-Japanese correlated with EQ-5D in the hypothesized magnitude and direction. Conclusions The newly developed MDASI-BT-Japanese has demonstrated feasibility, reliability and validity in evaluation of clinical benefit in Japanese-speaking brain tumor patients. </jats:sec