scholarly journals Membrane pools of phosphatidylinositol-4-phosphate regulate KCNQ1/KCNE1 membrane expression

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Chen Braun ◽  
Xiaorong Xu Parks ◽  
Haani Qudsi ◽  
Coeli M. B. Lopes
Keyword(s):  
Plasma Membrane ◽  
Ion Channel ◽  
Membrane Localization ◽  
Membrane Expression ◽  
Ion Channel Regulation ◽  
Channel Function ◽  
Channel Interactions ◽  
And Function ◽  
Phosphatidylinositol 4

AbstractPlasma membrane phosphatidylinositol 4-phosphate (PI4P) is a precursor of PI(4,5)P2, an important regulator of a large number of ion channels. Although the role of the phospholipid PI(4,5)P2 in stabilizing ion channel function is well established, little is known about the role of phospholipids in channel membrane localization and specifically the role of PI4P in channel function and localization. The phosphatidylinositol 4-kinases (PI4Ks) synthesize PI4P. Our data show that inhibition of PI4K and prolonged decrease of levels of plasma membrane PI4P lead to a decrease in the KCNQ1/KCNE1 channel membrane localization and function. In addition, we show that mutations linked to Long QT syndrome that affect channel interactions with phospholipids lead to a decrease in membrane expression. We show that expression of a LQT1-associated C-terminal deletion mutant abolishes PI4Kinase-mediated decrease in membrane expression and rescues membrane expression for phospholipid-targeting mutations. Our results indicate a novel role for PI4P on ion channel regulation. Our data suggest that decreased membrane PI4P availability to the channel, either due to inhibition of PI4K or as consequence of mutations, dramatically inhibits KCNQ1/KCNE1 channel membrane localization and current. Our results may have implications to regulation of other PI4P binding channels.

scholarly journals Influence of miR-221/222 on cardiomyocyte calcium handling and function

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Maria Knyrim ◽  
Sindy Rabe ◽  
Claudia Grossmann ◽  
Michael Gekle ◽  
Barbara Schreier
Keyword(s):  
Ion Channel ◽  
Current Density ◽  
Systolic Dysfunction ◽  
Calcium Handling ◽  
Electrical Remodeling ◽  
Ion Channel Regulation ◽  
Neonatal Cardiomyocytes ◽  
And Function ◽  
The Impact

Abstract Background Cardiovascular disease is the leading cause of death worldwide. Cardiac electrical remodeling including altered ion channel expression and imbalance of calcium homeostasis can have detrimental effects on cardiac function. While it has been extensively reported that miR-221/222 are involved in structural remodeling, their role in electrical remodeling still has to be evaluated. We previously reported that subunits of the L-type Ca2+ channel (LTCC) are direct targets of miR-221/222. Furthermore, HL-1 cells transfected with miR-221 or -222 mimics showed a reduction in LTCC current density while the voltage-dependence of activation was not altered. The aim of the present study was to determine the influence of miR-221/222 on cardiomyocyte calcium handling and function. Results Transient transfection of HL-1 cells with miR-221/222 mimics led to slower depolarization-dependent Ca2+ entry and increased proportion of non-responding cells. Angiotensin II-induced Ca2+ release from the SR was not affected by miR-221/222. In miR-222-transfected neonatal cardiomyocytes the isoprenaline-induced positive inotropic effect on the intracellular Ca2+ transient was lost and the positive chronotropic effect on spontaneous beating activity was strongly reduced. This could have severe consequences for cardiomyocytes and could lead to a reduced contractility and systolic dysfunction of the whole heart. Conclusions This study adds a new role of miR-221/222 in cardiomyocytes by showing the impact on β-adrenergic regulation of LTCC function, calcium handling and beating frequency. Together with the previous report that miR-221/222 reduce GIRK1/4 function and LTCC current density, it expands our knowledge about the role of these miRs on cardiac ion channel regulation.

Extracellular vesicle interplay in cardiovascular pathophysiology

2021 ◽  
Author(s):  
Sherin Saheera ◽  
Vivek P Jani ◽  
Kenneth W Witwer ◽  
Shelby Kutty
Keyword(s):  
Plasma Membrane ◽  
Cardiovascular System ◽  
Lipid Bilayer ◽  
Cellular Responses ◽  
Extracellular Vesicle ◽  
Cargo Proteins ◽  
And Function ◽  
Intercellular Communications ◽  
Rna And Dna

Extracellular vesicles (EVs) are nanosized lipid bilayer-delimited particles released from cells that mediate intercellular communications and play a pivotal role in various physiological and pathological processes. Subtypes of EVs may include plasma-membrane ectosomes or microvesicles and endosomal-origin exosomes, although functional distinctions remain unclear. EVs carry cargo proteins, nucleic acids (RNA and DNA), lipids, and metabolites. By presenting or transferring this cargo to recipient cells, EVs can trigger cellular responses. Here, we summarize what is known about EV biogenesis, composition, and function, with an emphasis on the role of EVs in cardiovascular system. Additionally, we provide an update on the function of EVs in cardiovascular pathophysiology, further highlighting their potential for diagnostic and therapeutic applications.

scholarly journals Mechanosensitive Ion Channel Piezo1 Regulates Myocyte Fusion during Skeletal Myogenesis

2020 ◽  
Author(s):  
Huascar Pedro Ortuste Quiroga ◽  
Shingo Yokoyama ◽  
Massimo Ganassi ◽  
Kodai Nakamura ◽  
Tomohiro Yamashita ◽  
...  
Keyword(s):  
Ion Channel ◽  
Molecular Mechanisms ◽  
Myoblast Fusion ◽  
Mechanical Stimuli ◽  
Muscle Satellite Cell ◽  
Myotube Formation ◽  
Mechanosensitive Ion Channel ◽  
And Function ◽  
Sirna Knockdown

AbstractMechanical stimuli such as stretch and resistance training are essential to regulate growth and function of skeletal muscle. However, the molecular mechanisms involved in sensing mechanical stress remain unclear. Here, the purpose of this study was to investigate the role of the mechanosensitive ion channel Piezo1 during myogenic progression. Muscle satellite cell-derived myoblasts and myotubes were modified with stretch, siRNA knockdown and agonist-induced activation of Piezo1. Direct manipulation of Piezo1 modulates terminal myogenic progression. Piezo1 knockdown suppressed myoblast fusion during myotube formation and maturation. This was accompanied by downregulation of the fusogenic protein Myomaker. Piezo1 knockdown also lowered Ca2+ influx in response to stretch. Conversely Piezo1 activation stimulated fusion and increased Ca2+ influx in response to stretch. These evidences indicate that Piezo1 is essential for myotube formation and maturation, which may have implications for msucular dystrophy prevention through its role as a mechanosensitive Ca2+ channel.

scholarly journals PI(4,5)P2 controls slit diaphragm formation and endocytosis in Drosophila nephrocytes

2021 ◽  
Author(s):  
Max Gass ◽  
Sarah Borkowsky ◽  
Marie-Luise Lotz ◽  
Rita Schroeter ◽  
Pavel Nedvetsky ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Model System ◽  
Dominant Negative ◽  
Slit Diaphragm ◽  
Phosphatidylinositol 3 Kinase ◽  
Ectopic Activation ◽  
Phosphatidylinositol 4 ◽  
Asymmetrically Distributed ◽  
Phosphatidylinositol 3

Drosophila nephrocytes are an emerging model system for mammalian podocytes and podocyte-associated diseases. Like podocytes, nephrocytes exhibit characteristics of epithelial cells, but the role of phospholipids in polarization of these cells is yet unclear. In epithelia phosphatidylinositol(4,5)bisphosphate (PI(4,5)P2) and phosphatidylinositol(3,4,5)-trisphosphate (PI(3,4,5)P3) are asymmetrically distributed in the plasma membrane and determine apical-basal polarity. Here we demonstrate that both phospholipids are present in the plasma membrane of nephrocytes, but only PI(4,5)P2 accumulates at slit diaphragms. Knockdown of Skittles, a phosphatidylinositol(4)phosphate 5-kinase, which produces PI(4,5)P2, abolished slit diaphragm formation and led to strongly reduced endocytosis. Notably, reduction in PI(3,4,5)P3 by overexpression of PTEN or expression of a dominant-negative phosphatidylinositol-3-Kinase did not affect nephrocyte function, whereas enhanced formation of PI(3,4,5)P3 by constitutively active phosphatidylinositol-3-Kinase resulted in strong slit diaphragm and endocytosis defects by ectopic activation of the Akt/mTOR pathway. Thus, PI(4,5)P2 but not PI(3,4,5)P3 is essential for slit diaphragm formation and nephrocyte function. However, PI(3,4,5)P3 has to be tightly controlled to ensure nephrocyte development.

scholarly journals Decrease in Multidrug Resistance-associated Protein 2 Activities by Knockdown of Phosphatidylinositol 4-phosphate 5-kinase in Hepatocytes and Cancer Cells

2019 ◽  
Vol 22 ◽  
pp. 576-584 ◽  
Author(s):  
Atsushi Kawase ◽  
Yuta Inoue ◽  
Miho Hirosoko ◽  
Yuka Sugihara ◽  
Hiroaki Shimada ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Multidrug Resistance ◽  
Cancer Cells ◽  
Hepg2 Cells ◽  
Carcinoma Cells ◽  
Efflux Transporters ◽  
Membrane Localization ◽  
Intracellular Accumulation ◽  
Primary Hepatocytes ◽  
Phosphatidylinositol 4

Purpose: The plasma membrane localization and transport activity of multidrug resistance-associated protein 2 (MRP2/ABCC2) and P-glycoprotein (P-gp/ABCB1) efflux transporters are governed by transporter-associated proteins. Phosphatidylinositol 4,5-bisphosphate (PIP2) formed by phosphatidylinositol 4-phosphate 5-kinase type 1 (PIP5K1) activates the linker function of radixin for efflux transporters. Radixin is involved in the plasma membrane localization of efflux transporters. We examined whether PIP5K1 could be a target for the modulation of transporter activities in hepatocytes and cancer cells. Methods: The effects of PIP5K1 depletion by siRNA in mouse primary hepatocytes, PANC1 human pancreatic carcinoma cells, and HepG2 human hepatocellular carcinoma cells on the intracellular accumulation of MRP2 and P-gp substrates were examined. Results: PIP5K1A depletion resulted in increased intracellular accumulation of carboxydichlorofluorescein, a MRP2 fluorescent substrate, in mouse primary hepatocytes, PANC1 cells, and HepG2 cells. In PANC1 and HepG2 cells, the transport activities of MRP2 were significantly decreased by PIP5K1C depletion. However, the transport activities of P-gp were unchanged by PIP5K1 depletion. PIP2 levels were unchanged between control and PIP5K1A- or PIP5K1C-depleted HepG2 cells. MRP2 mRNA levels showed few changes in HepG2 cells following PIP5K1A or PIP5K1C depletion. The expression of phosphorylated radixin was decreased by PIP5K1A and PIP5K1C depletion, although total radixin levels were unchanged. Conclusions: These data suggest that PIP5K1A and PIP5K1C could be target proteins for modulating MRP2 function, partly because of the resulting changes of the linker function of radixin.

scholarly journals Loss of P2X7 Receptor Plasma Membrane Expression and Function in Pathogenic B220+ Double-Negative T Lymphocytes of Autoimmune MRL/lpr Mice

PLoS ONE ◽  
2012 ◽  
Vol 7 (12) ◽  
pp. e52161 ◽  
Author(s):  
Sylvain M. Le Gall ◽  
Julie Legrand ◽  
Mohcine Benbijja ◽  
Hanaa Safya ◽  
Karim Benihoud ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
T Lymphocytes ◽  
P2x7 Receptor ◽  
Double Negative ◽  
Membrane Expression ◽  
Plasma Membrane Expression ◽  
And Function

Hereditary Thrombocytosis: The Thrombopoietin Receptor c-MPL Can Activate Its Downstream Pathway without Full Glycosylation and Membrane Expression

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 2374-2374
Author(s):  
Clemens Stockklausner ◽  
Nicole Echner ◽  
Anne-Christine Klotter ◽  
Isabelle Nadine Kuhlee ◽  
Andreas E Kulozik
Keyword(s):  
Plasma Membrane ◽  
Ligand Binding ◽  
Signaling Pathway ◽  
Conflicts Of Interest ◽  
Direct Consequence ◽  
Compound Heterozygous ◽  
Membrane Expression ◽  
Receptor Dimerization ◽  
Hereditary Thrombocytopenia ◽  
And Function

Abstract Abstract 2374 Thrombopoiesis is tightly regulated by the interaction between thrombopoietin (TPO) and its receptor c-Mpl. Receptor binding also leads to the clearance of TPO from the plasma thus establishing a negative feedback loop. However, it is still an open question how the receptor activates its downstream pathway. Alternative models posit that ligand binding either results in receptor dimerization in the plasma membrane or leads to conformational change of preformed receptor dimers. Several mutations in the TPO and the c-Mpl receptor genes have been linked to either hereditary thrombocytopenia or thrombocytosis. We focused on mutations in the extracellular part of the c-Mpl receptor, where ligand binding and receptor dimerization occur. Mutated homozygous c-Mpl R102P and compound heterozygous R102P/F104S receptors cause severe hereditary thrombocytopenia. In contrast, the homozygous c-Mpl P106L mutation was found in patients with hereditary thrombocytosis. We now addressed the question of how the disparate phenotype of mutations in the same domain of the c-Mpl receptor can be explained. We first functionally analyzed and compared normal with mutated R102P, F104S and P106L c-Mpl receptors in transfected HeLa and BA/F3 cells and found that the normal and the F104S c-Mpl receptors are glycosylated normally by the Golgi apparatus and reach the plasma membrane. In contrast, the R102P and P106L mutated receptors are not fully glycosylated, do not reach the plasma membrane and are atypically distributed in the ER. Functional analysis of the TPO/c-Mpl signaling pathway in BA/F3 cells showed decreased phosphorylation of Stat3, Stat5 and Erk1/2 with the R102P and F104S mutants when compared to normal. By contrast, TPO/c-Mpl signaling was up-regulated in cells transfected with the P106L-mutated receptor. Moreover, the P106L mutant, but not the other mutant receptors, enhanced ligand-independent growth of transfected BA/F3 cells. Despite of their opposite function, the TPO plasma levels of patients carrying both, homozygous R102P and P106L mutations were elevated 10 to 20-fold compared to normal and heterozygous individuals. This finding, together with their impaired glycosylation and inability to reach the plasma membrane, suggests that these mutants do not bind and internalize their ligand. TPO binding and degradation thus requires the receptor to be expressed at the plasma membrane, whereas, surprisingly, c-Mpl P106L activated its signaling pathway in a ligand independent fashion. Correct receptor processing and function can thus be separated. This indicates that TPO binding is required for regulation but that the constitutive activation of c-Mpl P106L is a likely direct consequence of premature receptor dimerization in the ER, auto-phosphorylation and subsequent activation of downstream targets. Disclosures: No relevant conflicts of interest to declare.

scholarly journals ENaC structure and function in the wake of a resolved structure of a family member

2011 ◽  
Vol 301 (4) ◽  
pp. F684-F696 ◽  
Author(s):  
Ossama B. Kashlan ◽  
Thomas R. Kleyman
Keyword(s):  
Plasma Membrane ◽  
Ion Channel ◽  
Functional Data ◽  
Ion Selectivity ◽  
External Environment ◽  
Structure And Function ◽  
Close Proximity ◽  
Channel Assembly ◽  
And Function ◽  
Insight Into

Our understanding of epithelial Na+ channel (ENaC) structure and function has been profoundly impacted by the resolved structure of the homologous acid-sensing ion channel 1 (ASIC1). The structure of the extracellular and pore regions provide insight into channel assembly, processing, and the ability of these channels to sense the external environment. The absence of intracellular structures precludes insight into important interactions with intracellular factors that regulate trafficking and function. The primary sequences of ASIC1 and ENaC subunits are well conserved within the regions that are within or in close proximity to the plasma membrane, but poorly conserved in peripheral domains that may functionally differentiate family members. This review examines functional data, including ion selectivity, gating, and amiloride block, in light of the resolved ASIC1 structure.

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