The ubiquitously expressed family of inward rectifier potassium (KIR) channels, encoded by KCNJ genes, is primarily involved in cell excitability and potassium homeostasis. Channel mutations associate with a variety of severe human diseases and syndromes, affecting many organ systems including the central and peripheral neural system, heart, kidney, pancreas, and skeletal muscle. A number of mutations associate with altered ion channel expression at the plasma membrane, which might result from defective channel trafficking. Trafficking involves cellular processes that transport ion channels to and from their place of function. By alignment of all KIR channels, and depicting the trafficking associated mutations, three mutational hotspots were identified. One localized in the transmembrane-domain 1 and immediately adjacent sequences, one was found in the G-loop and Golgi-export domain, and the third one was detected at the immunoglobulin-like domain. Surprisingly, only few mutations were observed in experimentally determined Endoplasmic Reticulum (ER)exit-, export-, or ER-retention motifs. Structural mapping of the trafficking defect causing mutations provided a 3D framework, which indicates that trafficking deficient mutations form clusters. These “mutation clusters” affect trafficking by different mechanisms, including protein stability.

Inward rectifier potassium ion channels (IK1-channels) of the Kir2.x family are responsible for maintaining a stable negative resting membrane potential in excitable cells, but also play a role in processes of non-excitable tissues, such as bone development. IK1-channel loss-of-function, either congenital or acquired, has been associated with cardiac disease. Currently, basic research and specific treatment are hindered by the absence of specific and efficient Kir2.x channel activators. However, twelve different compounds, including approved drugs, show off-target IK1 activation. Therefore, these compounds contain valuable information towards the development of agonists of Kir channels, AgoKirs. We reviewed the mechanism of IK1 channel activation of these compounds, which can be classified as direct or indirect activators. Subsequently, we examined the most viable starting points for rationalized drug development and possible safety concerns with emphasis on cardiac and skeletal muscle adverse effects of AgoKirs. Finally, the potential value of AgoKirs is discussed in view of the current clinical applications of potentiators and activators in cystic fibrosis therapy.

This work presents drug-likeness and the cardiotoxicity profiles of six potent pentamidine analogs 1-6 and three new compounds 7-9 as chemotherapeutics for therapy of Pneumocystis jiroveci pneumonia. A combination of experimental and computational approaches was used in the cardiotoxicity examination. The hERG trafficking and functionality of the hERG currents were tested by western blot analyses, immunofluorescent staining procedures, and patch-clamp electrophysiological assays. Cardiotoxicity combined with blocking the hERG K + channel was predicted, and then simulated by docking to the CSM-TM model 732 protein. Location of pentamidines in the proximity of Leu622, Thr623, Ser649, Tyr652, Ala653, and Phe656, and the high energies of interactions were in accordance with probable blocking of the hERG channel. However, in the biochemical experiments, no significant changes in I hERG densities and a minor effect on hERG maturation were observed. Predicted metabolic transformation of pentamidines with S atoms in the aliphatic linker leads to oxidation of one S atom, but those with the phenyl sulfanilide moiety can be oxidized to chinones. The tested pentamidines characterized by the presence of sulfur atoms or sulfanilide groups, have favorable drug-likeness parameters and are promising lead structures in the development of new potent chemotherapeutics against PJP.All studied pentamidines 1-9 are analyzed in the dicationic form. The predicted drug-likeness parameters (the topological 38360 | RSC Adv., 2019,9,[38355][38356][38357][38358][38359][38360][38361][38362][38363][38364][38365][38366][38367][38368][38369][38370][38371] This journal is View Article Online were predicted to be above 4 indicating a higher risk for hERG K + channel inhibition. 68 We also examined logarithm of the distribution coefficient values (log D) at pH 7.4, which give an estimate of the lipophilicity of a drug at the pH of blood plasma. The average values of log D are within the range À0.03 to 2.75 and not exceeding the traditionally cutoff value of 3.5. Fig. 3 Products of metabolism of pentamidine and 1-9 derivatives.This journal is

Inter-cellular heterogeneity is central to the dynamic range and robustness of function in many tissues, particularly electrically excitable tissues. In pancreatic islet 𝛽-cells, inter-cellular heterogeneity underlies the range of insulin response to glucose. In human-induced-pluripotent stem cell-derived cardiomyocytes (hiPSCCMs), inter-cellular heterogeneity presents a key challenge for drug screening applications. In this study, we assess the ability to reconstruct inter-cellular heterogeneity in silico by applying a “population of models” (PoMs) framework, i.e. collections of computational cells created via Monte Carlo variation of model parameters. We define parameter variation based on experimentally observed heterogeneity in properties such as ion current conductances and enzymatic affinities. We then assess the accuracy of those reconstructions, based on the degree to which variation in PoM outputs (e.g. action potential duration) matches experimentally observed variation. We report that this “ground-up” approach underestimates functional heterogeneity in the hiPSC-CM population, but overestimates it in adult human cardiomyocytes. In contrast, the 𝛽-cell PoM captures three distinct and physiologically relevant subclasses of 𝛽-cell function. In the future, we expect PoM approaches like these willpermit incorporation of realistic cellular heterogeneity in detailed models of intact tissues, and thereby aid development of sophisticated tissue-engineered platforms for therapeutics.