Roles of LRRC26 as an auxiliary γ1-subunit of large-conductance Ca2+-activated K+ channels in bronchial smooth muscle cells

A drug-free cardiovascular stent functionalized with tailored collagen supports in-situ healing of vascular tissues

Drug-eluting stent implantation suppresses the excessive proliferation of smooth muscle cells to reduce in-stent restenosis. However, the efficacy of drug-eluting stents remains limited due to delayed reendothelialization, impaired intimal remodeling, and potentially increased late restenosis. Here, we show that a drug-free coating formulation functionalized with tailored recombinant humanized type III collagen exerts one-produces-multi effects in response to injured tissue following stent implantation. We demonstrate that the one-produces-multi coating possesses anticoagulation, anti-inflammatory, and intimal hyperplasia suppression properties. We perform transcriptome analysis to indicate that the drug-free coating favors the endothelialization process and induces the conversion of smooth muscle cells to a contractile phenotype. We find that compared to drug-eluting stents, our drug-free stent reduces in-stent restenosis in rabbit and porcine models and improves vascular neointimal healing in a rabbit model. Collectively, the one-produces-multi drug-free system represents a promising strategy for the next-generation of stents.

Hereditary Basis of Coat Color and Excellent Feed Conversion Rate of Red Angus Cattle by Next-Generation Sequencing Data

Angus cattle have made remarkable contributions to the livestock industry worldwide as a commercial meat-type breed. Some evidence supported that Angus cattle with different coat colors have different feed-to-meat ratios, and the genetic basis of their coat color is inconclusive. Here, genome-wide association study was performed to investigate the genetic divergence of black and red Angus cattle with 63 public genome sequencing data. General linear model analysis was used to identify genomic regions with potential candidate variant/genes that contribute to coat color and feed conversion rate. Results showed that six single nucleotide polymorphisms (SNPs) and two insertion−deletions, which were annotated in five genes (ZCCHC14, ANKRD11, FANCA, MC1R, and LOC532875 [AFG3-like protein 1]), considerably diverged between black and red Angus cattle. The strongest associated loci, namely, missense mutation CHIR18_14705671 (c.296T > C) and frameshift mutation CHIR18_12999497 (c.310G>-), were located in MC1R. Three consecutive strongly associated SNPs were also identified and located in FANCA, which is widely involved in the Fanconi anemia pathway. Several SNPs of highly associated SNPs was notably enriched in ZCCHC14 and ANKRD11, which are related to myofiber growth and muscle development. This study provides a basis for the use of potential genetic markers to be used in future breeding programs to improve cattle selection in terms of coat color and meat phenotype. This study is also helpful to understand the hereditary basis of different coat colors and meat phenotypes. However, the putative candidate genes or markers identified in this study require further investigation to confirm their phenotypic causality and potential effective genetic relationships.

The LRRC family of BK channel regulatory subunits: potential roles in health and disease

Large conductance K⁺ channels, termed BK channels, regulate a variety of cellular and physiological functions. Although universally activated by changes in voltage or [Ca²⁺ ]_i , the threshold for BK channel activation varies among loci of expression, often arising from cell-specific regulatory subunits including a family of leucine rich repeat-containing (LRRC) γ subunits (LRRC26, LRRC52, LRRC55 and LRRC38). The 'founding' member of this family, LRRC26, was originally identified as a tumour suppressor in various cancers. An LRRC26 knockout (KO) mouse model recently revealed that LRRC26 is also highly expressed in secretory epithelial cells and partners with BK channels in the salivary gland and colonic goblet cells to promote sustained K⁺ fluxes likely essential for normal secretory function. To accomplish this, LRRC26 negatively shifts the range of BK channel activation such that channels contribute to K⁺ flux near typical epithelial cell resting conditions. In colon, the absence of LRRC26 increases vulnerability to colitis. LRRC26-containing BK channels are also likely important regulators of epithelial function in other loci, including airways, female reproductive tract and mammary gland. Based on an LRRC52 KO mouse model, LRRC52 regulation of large conductance K⁺ channels plays a role both in sperm function and in cochlear inner hair cells. Although our understanding of LRRC-containing BK channels remains rudimentary, KO mouse models may help define other organs in which LRRC-containing channels support normal function. A key topic for future work concerns identification of endogenous mechanisms, whether post-translational or via gene regulation, that may impact LRRC-dependent pathologies.

Reciprocal Relationship between Ca2+ Signaling and Ca2+-Gated Ion Channels as a Potential Target for Drug Discovery

Cellular Ca²⁺ signaling functions as one of the most common second messengers of various signal transduction pathways in cells and mediates a number of physiological roles in a cell-type dependent manner. Ca²⁺ signaling also regulates more general and fundamental cellular activities, including cell proliferation and apoptosis. Among ion channels, Ca²⁺-permeable channels in the plasma membrane as well as endo- and sarcoplasmic reticulum membranes play important roles in Ca²⁺ signaling by directly contributing to the influx of Ca²⁺ from extracellular spaces or its release from storage sites, respectively. Furthermore, Ca²⁺-gated ion channels in the plasma membrane often crosstalk reciprocally with Ca²⁺ signals and are central to the regulation of cellular functions. This review focuses on the physiological and pharmacological impact of i) Ca²⁺-gated ion channels as an apparatus for the conversion of cellular Ca²⁺ signals to intercellularly propagative electrical signals and ii) the opposite feedback regulation of Ca²⁺ signaling by Ca²⁺-gated ion channel activities in excitable and non-excitable cells.

Single Molecule Fluorescence Imaging Reveals the Stoichiometry of BKγ1 Subunit in Living HEK293 Cell Expression System

Large conductance Ca²⁺-activated K⁺ (BK_Ca) channels are ubiquitously expressed in plasma membrane of both excitable and non-excitable cells and possess significant physiological functions. A tetrameric complex of α subunit (BKα) forms a functional pore of BK_Ca channel. The properties of BK_Ca channel, such as voltage-dependence, Ca²⁺ sensitivity and pharmacological responses, are extensively modulated by co-expressing accessory β subunits (BKβ), which can associate with BKα in one to one manner. Although the functional significance of newly identified γ subunits (BKγ) has been revealed, the stoichiometry between BKα and BKγ1 remains unclear. In the present study, we utilized a single molecule fluorescence imaging with a total internal reflection fluorescence (TIRF) microscope to directly count the number of green fluorescent protein (GFP)-tagged BKγ1 (BKγ1-GFP) within a single BK_Ca channel complex in HEK293 cell expression system. BKγ1-GFP significantly enhanced the BK channel activity even when the intracellular Ca²⁺ concentration was kept lower, i.e., 10 nM, than the physiological resting level. BKγ1-GFP stably formed molecular complexes with BKα-mCherry in the plasma membrane. Counting of GFP bleaching steps revealed that a BK_Ca channel can contain up to four BKγ1 per channel at the maximum. These results suggest that BKγ1 forms a BK_Ca channel complex with BKα in a 1 : 1 stoichiometry in a human cell line.

K+ and Ca2+ Channels Regulate Ca2+ Signaling in Chondrocytes: An Illustrated Review

An improved understanding of fundamental physiological principles and progressive pathophysiological processes in human articular joints (e.g., shoulders, knees, elbows) requires detailed investigations of two principal cell types: synovial fibroblasts and chondrocytes. Our studies, done in the past 8–10 years, have used electrophysiological, Ca²⁺ imaging, single molecule monitoring, immunocytochemical, and molecular methods to investigate regulation of the resting membrane potential (E_R) and intracellular Ca²⁺ levels in human chondrocytes maintained in 2-D culture. Insights from these published papers are as follows: (1) Chondrocyte preparations express a number of different ion channels that can regulate their E_R. (2) Understanding the basis for E_R requires knowledge of (a) the presence or absence of ligand (ATP/histamine) stimulation and (b) the extraordinary ionic composition and ionic strength of synovial fluid. (3) In our chondrocyte preparations, at least two types of Ca²⁺-activated K⁺ channels are expressed and can significantly hyperpolarize E_R. (4) Accounting for changes in E_R can provide insights into the functional roles of the ligand-dependent Ca²⁺ influx through store-operated Ca²⁺ channels. Some of the findings are illustrated in this review. Our summary diagram suggests that, in chondrocytes, the K⁺ and Ca²⁺ channels are linked in a positive feedback loop that can augment Ca²⁺ influx and therefore regulate lubricant and cytokine secretion and gene transcription.

Involvement of the γ1 subunit of the large-conductance Ca2+-activated K+ channel in the proliferation of human somatostatinoma cells

Pancreatic neuroendocrine tumors (pNETs) occur due to the abnormal growth of pancreatic islet cells and predominantly develop in the duodenal-pancreatic region. Somatostatinoma is one of the pNETs associated with tumors of pancreatic δ cells, which produce and secrete somatostatin. Limited information is currently available on the pathogenic mechanisms of somatostatinoma. The large-conductance Ca²⁺-activated K⁺ (BK_Ca) channel is expressed in several types of cancer cells and regulates cell proliferation, migration, invasion, and metastasis. In the present study, the functional expression of the BK_Ca channel was examined in a human somatostatinoma QGP-1 cell line. In QGP-1 cells, outward currents were elicited by membrane depolarization at pCa 6.5 (300 nM) in the pipette solution and inhibited by the specific BK_Ca channel blocker, paxilline. Paxilline-sensitive currents were detected, even at pCa 8.0 (10 nM) in the pipette solution, in QGP-1 cells. In addition to the α and β2-4 subunits of the BK_Ca channel, the novel regulatory γ1 subunit (BK_Caγ1) was co-localized with the α subunit in QGP-1 cells. Paxilline-sensitive currents at pCa 8.0 in the pipette solution were reduced by the siRNA knockdown of BK_Caγ1. Store-operated Ca²⁺ entry was smaller in BK_Caγ1 siRNA-treated QGP-1 cells. The proliferation of QGP-1 cells was attenuated by paxilline or the siRNA knockdown of BK_Caγ1. These results strongly suggest that BK_Caγ1 facilitates the proliferation of human somatostatinoma cells. Therefore, BK_Caγ1 may be a novel therapeutic target for somatostatinoma.