Chloride is a key anion involved in cellular physiology by regulating its homeostasis and rheostatic processes. Changes in cellular Cl− concentration result in differential regulation of cellular functions such as transcription and translation, post-translation modifications, cell cycle and proliferation, cell volume, and pH levels. In intracellular compartments, Cl− modulates the function of lysosomes, mitochondria, endosomes, phagosomes, the nucleus, and the endoplasmic reticulum. In extracellular fluid (ECF), Cl− is present in blood/plasma and interstitial fluid compartments. A reduction in Cl− levels in ECF can result in cell volume contraction. Cl− is the key physiological anion and is a principal compensatory ion for the movement of the major cations such as Na+, K+, and Ca2+. Over the past 25 years, we have increased our understanding of cellular signaling mediated by Cl−, which has helped in understanding the molecular and metabolic changes observed in pathologies with altered Cl− levels. Here, we review the concentration of Cl− in various organs and cellular compartments, ion channels responsible for its transportation, and recent information on its physiological roles.

Mitochondrial-associated membranes (MAMs) are known to modulate organellar and cellular functions and can subsequently affect pathophysiology including myocardial ischemia-reperfusion (IR) injury. Thus, identifying molecular targets in MAMs that regulate the outcome of IR injury will hold a key to efficient therapeutics. Here, we found chloride intracellular channel protein (CLIC4) presence in MAMs of cardiomyocytes and demonstrate its role in modulating ER and mitochondrial calcium homeostasis under physiological and pathological conditions. In a murine model, loss of CLIC4 increased myocardial infarction and substantially reduced cardiac function after IR injury. CLIC4 null cardiomyocytes showed increased apoptosis and mitochondrial dysfunction upon hypoxia-reoxygenation injury in comparison to wild-type cardiomyocytes. Overall, our results indicate that MAM-CLIC4 is a key mediator of cellular response to IR injury and therefore may have a potential implication on other pathophysiological processes.

Chloride intracellular channels (CLICs) are a family of proteins that exist in soluble and transmembrane forms. The newest discovered member of the family CLIC6 is implicated in breast, ovarian, lung gastric, and pancreatic cancers, and is also known to interact with dopamine-(D(2)-like) receptors. The soluble structure of the channel has been resolved but the exact physiological role of CLIC6, biophysical characterization, and the membrane structure remains unknown. Here we aimed to characterize the biophysical properties of this channel using a patch-clamp approach. To determine the biophysical properties of CLIC6, we expressed CLIC6 in HEK-293 cells. On ectopic expression, CLIC6 localizes to the plasma membrane of HEK-293 cells. We established the biophysical properties of CLIC6 by using whole-cell, and cell-attached configurations. Using various anions and potassium (K⁺) solutions, we determined that CLIC6 is more permeable to chloride-(Cl^-) as compared to bromide-(Br^-), fluoride-(F^-), and K⁺ ions. In the whole-cell configuration, the CLIC6 currents were inhibited after the addition of 10 μM of IAA-94 (CLIC-specific blocker). CLIC6 was also found to be regulated by pH and redox potential. We demonstrate that the histidine residue at 648 (H648) in the C-terminus, and cysteine residue in the N-terminus (C487) are directly involved in the pH-induced conformational change and redox regulation of CLIC6, respectively. Using qRT-PCR, we identified that CLIC6 is most abundant in the lung and brain, and we recorded the CLIC6 current in Mouse Lung Epithelial (MLE) cells. Overall, we have determined the biophysical properties of CLIC6 and established it as a Cl^- channel.

Protein arginine methyltransferase (PRMT) 5 is the type 2 methyltransferase catalyzing symmetric dimethylation of arginine. PRMT5 inhibition or deletion in CD4 Th cells reduces TCR engagement-induced IL-2 production and Th cell expansion and confers protection against experimental autoimmune encephalomyelitis, the animal model of multiple sclerosis. However, the mechanisms by which PRMT5 modulates Th cell proliferation are still not completely understood, and neither are the methylation targets in T cells. In this manuscript, we uncover the role of PRMT5 on alternative splicing in activated mouse T cells and identify several targets of PRMT5 symmetric dimethylation involved in splicing. In addition, we find a possible link between PRMT5-mediated alternative splicing of transient receptor potential cation channel subfamily M member 4 (Trpm4) and TCR/NFAT signaling/IL-2 production. This understanding may guide development of drugs targeting these processes to benefit patients with T cell–mediated diseases.

Cancer and heart diseases are the two leading causes of mortality and morbidity worldwide. Many cancer patients undergo heart-related complications resulting in high incidences of mortality. It is generally hypothesized that cardiac dysfunction in cancer patients occurs due to cardiotoxicity induced by therapeutic agents, used to treat cancers and/or cancer-induced cachexia. However, it is not known if localized tumors or unregulated cell growth systemically affect heart function before treatment, and/or prior to the onset of cachexia, hence, making the heart vulnerable to structural or functional abnormalities in later stages of the disease. We incorporated complementary mouse and Drosophila models to establish if tumor induction indeed causes cardiac defects even before intervention with chemotherapy or onset of cachexia. We focused on one of the key pathways involved in irregular cell growth, the Hippo–Yorkie (Yki), pathway. We used overexpression of the transcriptional co-activator of the Yki signaling pathway to induce cellular overgrowth, and show that Yki overexpression in the eye tissue of Drosophila results in compromised cardiac function. We rescue these cardiac phenotypes using antioxidant treatment, with which we conclude that the Yki induced tumorigenesis causes a systemic increase in ROS affecting cardiac function. Our results show that systemic cardiac dysfunction occurs due to abnormal cellular overgrowth or cancer elsewhere in the body; identification of specific cardiac defects associated with oncogenic pathways can facilitate the possible early diagnosis of cardiac dysfunction.

Aim: The present study aims to compare the cytoprotective effect of Cuminum cyminum L. (CC) extract and cuminaldehyde (CA) against lipotoxicity induced by oxidized low density lipoprotein (Ox-LDL) in mouse macrophage (RAW 264.7) cells.Objective: To assess comparative Cytoprotective potential of CC and CA against Ox-LDL induced cytotoxicity. ii) To study efficacy of CC and CA in preventing Ox-LDL induced apoptosisMethods: Protective effect of CC extract and CA aganist Ox-LDL induced cytotoxicity in RAW 264.7 cells was assessed by MTT assay. DCFDA stain was used to check the generation of ROS followed by analysis of apoptotic genes by quantitative RT-PCR.Results: CC extract was found to be non-toxic up to 300 μg/ml but CA showed significant toxicity from 50 to 300 μg/ml. Cells treated with Ox-LDL recorded 80 % decrement in cell viability as compared to the control cells. But Ox-LDL+CC treated group accounted for improved cell viability (88 %) which was comparable to that of control. However, Ox-LDL+CA treated cells did not record any improvement in cell viability (19 %). DCF-DA staining revealed that the presence of CC could minimize intracellular oxidative stress but similarly this was persistent in CA supplemented group. Furthermore, mRNA expression of apoptotic genes revealed that Ox-LDL induced upregulation of Bax and downregulation of Bcl-2 genes were not recorded in Ox-LDL+CC treated group.Conclusion: It can be concluded that CC extract efficiently prevented Ox-LDL induced lipotoxicity and apoptosis and has an anti-atherosclerotic potential. The failure of CA emphasizes the importance of naturally occurring polyherbal formulations over pure compounds in imparting bioactivity and for therapeutic applications.