Small ubiquitin-related modifiers, SUMO-2/3 and SUMO-1, are involved in gene regulation and nuclear structures. However, little is known about the roles of SUMO, in heterochromatin formation of mammalian cells. Here we demonstrate that SUMOs directly interact with human MCAF1, which forms complexes with either the methyl-CpG-binding protein MBD1 or SETDB1, which trimethylates histone H3 at lysine 9 (H3-K9) in the presence of MCAF1. Modification of MBD1 with either SUMO-2/3 or SUMO-1 facilitated the interaction between MBD1 and MCAF1, suggesting that SUMOylation links the methylation of DNA and histones. In a cultured human cell line, SUMOs were localized in MBD1- and MCAF1-containing heterochromatin regions that were enriched in trimethyl-H3-K9 and the heterochromatin proteins HP1β and HP1γ. Specific knockdown of either SUMO-2/3 or SUMO-1 induced dissociation of MCAF1, trimethyl-H3-K9, and the HP1 proteins from the MBD1-containing heterochromatin foci, suggesting a requirement for SUMOs for heterochromatin assembly. These findings provide insights into the roles of SUMOylation in the regulation of heterochromatin formation and gene silencing.

Oncotarget | https://doi.org/10.18632/oncotarget.25809 Mamiko Kobayashi, Daisuke Mikami, Junsuke Uwada, Takashi Yazawa, Kazuko Kamiyama, Hideki Kimura, Takanobu Taniguchi, Masayuki Iwano A short-chain fatty acid, propionate, enhances the cytotoxic effect of cisplatin by modulating GPR41 signaling pathways in HepG2 cells

BACKGROUND AND PURPOSE Muscarinic acetylcholine receptors (mAChRs) and β‐adrenoceptors in the airways and lungs are clinically important in chronic obstructive pulmonary disease (COPD) and asthma. However, the quantitative and qualitative estimation of these receptors by radioligand binding approaches in human airways has not yet been reported because of tissue limitations.EXPERIMENTAL APPROACH The regional distribution and relative proportion of mAChR and β‐adrenoceptor subtypes were evaluated in human bronchus and lung parenchyma by a tissue segment binding method with [³H]‐N‐methylscopolamine ([³H]‐NMS) for mAChRs and [³H]‐CGP‐12,177 for β‐adrenoceptors. Functional responses to carbachol and isoprenaline were also analysed in the bronchus.KEY RESULTS The M₃ subtype predominantly occurred in the bronchus, but the density decreased from the segmental to subsegmental bronchus, and was absent in lung parenchyma. On the other hand, the M₁ subtype occurred in the lung only, and the M₂ subtype was distributed ubiquitously in the bronchus and lungs. β₂‐adrenoceptors were increased along the airways, and their densities in the subsegmental bronchus and lung parenchyma were approximately twofold higher than those of mAChRs in the same region. β₁‐adrenoceptors were also detected in lung parenchyma but not in the bronchus. The muscarinic contractions and adrenoceptor relaxations in both bronchial regions were mediated through M₃‐mAChRs and β₂‐adrenoceptors, respectively.CONCLUSIONS AND IMPLICATIONS From the present radioligand binding approach with intact tissue segments, we constructed a distribution map of mAChRs and β‐adrenoceptors in human bronchus and lung parenchyma for the first time, providing important evidence for future pharmacotherapy and new drug development for respiratory disorders.

Inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, is an intestinal disorder that causes prolonged inflammation of the gastrointestinal tract. Currently, the etiology of IBD is not fully understood and treatments are insufficient to completely cure the disease. In addition to absorbing essential nutrients, intestinal epithelial cells prevent the entry of foreign antigens (micro-organisms and undigested food) through mucus secretion and epithelial barrier formation. Disruption of the intestinal epithelial homeostasis exacerbates inflammation. Thus, the maintenance and reinforcement of epithelial function may have therapeutic benefits in the treatment of IBD. Muscarinic acetylcholine receptors (mAChRs) are G protein-coupled receptors for acetylcholine that are expressed in intestinal epithelial cells. Recent studies have revealed the role of mAChRs in the maintenance of intestinal epithelial homeostasis. The importance of non-neuronal acetylcholine in mAChR activation in epithelial cells has also been recognized. This review aimed to summarize recent advances in research on mAChRs for intestinal epithelial homeostasis and the involvement of non-neuronal acetylcholine systems, and highlight their potential as targets for IBD therapy.

Ovaries represent one of the primary steroidogenic organs, producing estrogen and progesterone under the regulation of gonadotropins during the estrous cycle. Gonadotropins fluctuate the expression of various steroidogenesis-related genes, such as those encoding steroidogenic enzymes, cholesterol deliverer, and electronic transporter. Steroidogenic factor-1 (SF-1)/adrenal 4-binding protein (Ad4BP)/NR5A1 and liver receptor homolog-1 (LRH-1) play important roles in these phenomena via transcriptional regulation. With the aid of cAMP, SF-1/Ad4BP and LRH-1 can induce the differentiation of stem cells into steroidogenic cells. This model is a useful tool for studying the molecular mechanisms of steroidogenesis. In this article, we will provide insight into the transcriptional regulation of steroidogenesis-related genes in ovaries that are revealed from stem cell-derived steroidogenic cells. Using the cells derived from the model, novel SF-1/Ad4BP- and LRH-1-regulated genes were identified by combined DNA microarray and promoter tiling array analyses. The interaction of SF-1/Ad4BP and LRH-1 with transcriptional regulators in the regulation of ovarian steroidogenesis was also revealed.

Muscarinic acetylcholine receptors (mAChRs) are well known to transmit extracellular cholinergic signals into the cytoplasm from their position on the cell surface. However, we show here that M1‐mAChRs are also highly expressed on intracellular membranes in neurons of the telencephalon and activate signaling cascades distinct from those of cell surface receptors, contributing uniquely to synaptic plasticity. Radioligand‐binding experiments with cell‐permeable and ‐impermeable ligands and immunohistochemical observations revealed intracellular and surface distributions of M1‐mAChRs in the hippocampus and cortex of rats, mice, and humans, in contrast to the selective occurrence on the cell surface in other tissues. All intracellular muscarinic‐binding sites were abolished in M1‐mAChR‐gene‐knockout mice. Activation of cell surface M1‐mAChRs in rat hippocampal neurons evoked phosphatidylinositol hydrolysis and network oscillations at theta rhythm, and transiently enhanced long‐term potentiation. On the other hand, activation of intracellular M1‐mAChRs phosphorylated extracellular‐regulated kinase 1/2 and gradually enhanced long‐term potentiation. Our data thus demonstrate that M1‐mAChRs function at both surface and intracellular sites in telencephalon neurons including the hippocampus, suggesting a new mode of cholinergic transmission in the central nervous system.