Chemiluminescence Assays to Investigate Membrane Expression and Clathrin-Mediated Endocytosis of KATP Channels

2008 ◽  
pp. 63-68 ◽  
Author(s):  
Andrew J. Smith ◽  
Asipu Sivaprasadarao
Keyword(s):  
Katp Channels ◽  
Membrane Expression

Molecular Basis and Clinical Aspects of Hereditary Megakaryocyte and Platelet Membrane Glycoprotein Disorders

1996 ◽  
Vol 16 (02) ◽  
pp. 114-138 ◽  
Author(s):  
R. E. Scharf
Keyword(s):  
Genetic Basis ◽  
Molecular Mechanisms ◽  
Molecular Genetic ◽  
Platelet Membrane ◽  
Clinical Aspects ◽  
Membrane Glycoprotein ◽  
Membrane Glycoproteins ◽  
Membrane Expression ◽  
Receptor Complexes ◽  
Platelet Membrane Glycoprotein

SummarySpecific membrane glycoproteins (GP) expressed by the megakaryocyte-platelet system, including GPIa-lla, GPIb-V-IX, GPIIb-llla, and GPIV are involved in mediat-ing platelet adhesion to the subendothelial matrix. Among these glycoproteins, GPIIb-llla plays a pivotal role since platelet aggregation is exclusively mediated by this receptor and its interaction with soluble macromolecular proteins. Inherited defects of the GPIIb-llla or GPIb-V-IX receptor complexes are associated with bleeding disorders, known as Glanzmann's thrombasthenia, Bernard-Soulier syndrome, or platelet-type von Willebrand's disease, respectively. Using immuno-chemical and molecular biology techniques, rapid advances in our understanding of the molecular genetic basis of these disorders have been made during the last few years. Moreover, analyses of patients with congenital platelet membrane glycoprotein abnormalities have provided valuable insights into molecular mechanisms that are required for structural and functional integrity, normal biosynthesis of the glycoprotein complexes and coordinated membrane expression of their constituents. The present article reviews the current state of knowledge of the major membrane glycoproteins in health and disease. The spectrum of clinical bleeding manifestations and established diagnostic criteria for each of these dis-orders are summarized. In particular, the variety of molecular defects that have been identified so far and their genetic basis will be discussed.

Central KATP channels modulate glucose effectiveness in humans and rodents

2020 ◽  
Author(s):  
Ada Admin ◽  
Michelle Carey ◽  
Eric Lontchi-Yimagou ◽  
William Mitchell ◽  
Sarah Reda ◽  
...  
Keyword(s):  
Katp Channel ◽  
Glucose Production ◽  
Katp Channels ◽  
Endogenous Glucose Production ◽  
Elevated Plasma ◽  
Sprague Dawley ◽  
Glucose Effectiveness ◽  
Sprague Dawley Rats ◽  
The Central Nervous System

Hyperglycemia is a potent regulator of endogenous glucose production (EGP). Loss of this ‘glucose effectiveness’ is a major contributor to elevated plasma glucose concentrations in type 2 diabetes (T2D). ATP-sensitive potassium channels (K<sub>ATP</sub> channels) in the central nervous system (CNS) have been shown to regulate EGP in humans and rodents. We examined the contribution of central K<sub>ATP</sub> channels to glucose effectiveness. Under fixed hormonal conditions (‘pancreatic clamp’ studies), hyperglycemia suppressed EGP by ~50% in both non-diabetic humans and normal Sprague Dawley rats. By contrast, antagonism of K<sub>ATP</sub> channels with glyburide significantly reduced the EGP-lowering effect of hyperglycemia in both humans and rats. Furthermore, the effects of glyburide on EGP and gluconeogenic enzymes in rats were abolished by intracerebroventricular (ICV) administration of the KATP channel agonist diazoxide. These findings indicate that about half of EGP suppression by hyperglycemia is mediated by central K<sub>ATP</sub> channels. These central mechanisms may offer a novel therapeutic target for improving glycemic control in T2D.

Molecular Mechanisms of the Inhibitory Effects of Bupivacaine, Levobupivacaine, and Ropivacaine on Sarcolemmal Adenosine Triphosphate–sensitive Potassium Channels in the Cardiovascular System

2004 ◽  
Vol 101 (2) ◽  
pp. 390-398 ◽  
Author(s):  
Takashi Kawano ◽  
Shuzo Oshita ◽  
Akira Takahashi ◽  
Yasuo Tsutsumi ◽  
Yoshinobu Tomiyama ◽  
...  
Keyword(s):  
Cardiovascular System ◽  
Adenosine Triphosphate ◽  
Local Anesthetics ◽  
Molecular Mechanisms ◽  
Transmembrane Domain ◽  
Katp Channels ◽  
Inhibitory Effect ◽  
Amino Acid Residues ◽  
Sulfonylurea Receptor ◽  
Inhibitory Effects

Background Sarcolemmal adenosine triphosphate-sensitive potassium (KATP) channels in the cardiovascular system may be involved in bupivacaine-induced cardiovascular toxicity. The authors investigated the effects of local anesthetics on the activity of reconstituted KATP channels encoded by inwardly rectifying potassium channel (Kir6.0) and sulfonylurea receptor (SUR) subunits. Methods The authors used an inside-out patch clamp configuration to investigate the effects of bupivacaine, levobupivacaine, and ropivacaine on the activity of reconstituted KATP channels expressed in COS-7 cells and containing wild-type, mutant, or chimeric SURs. Results Bupivacaine inhibited the activities of cardiac KATP channels (IC50 = 52 microm) stereoselectively (levobupivacaine, IC50 = 168 microm; ropivacaine, IC50 = 249 microm). Local anesthetics also inhibited the activities of channels formed by the truncated isoform of Kir6.2 (Kir6.2 delta C36) stereoselectively. Mutations in the cytosolic end of the second transmembrane domain of Kir6.2 markedly decreased both the local anesthetics' affinity and stereoselectivity. The local anesthetics blocked cardiac KATP channels with approximately eightfold higher potency than vascular KATP channels; the potency depended on the SUR subtype. The 42 amino acid residues at the C-terminal tail of SUR2A, but not SUR1 or SUR2B, enhanced the inhibitory effect of bupivacaine on the Kir6.0 subunit. Conclusions Inhibitory effects of local anesthetics on KATP channels in the cardiovascular system are (1) stereoselective: bupivacaine was more potent than levobupivacaine and ropivacaine; and (2) tissue specific: local anesthetics blocked cardiac KATP channels more potently than vascular KATP channels, via the intracellular pore mouth of the Kir6.0 subunit and the 42 amino acids at the C-terminal tail of the SUR2A subunit, respectively.

scholarly journals Loss of SUR1 subtype KATP channels alters antinociception and locomotor activity after opioid administration

2021 ◽  
pp. 113467
Author(s):  
Gerald Sakamaki ◽  
Kayla Johnson ◽  
Megan Mensinger ◽  
Eindray Hmu ◽  
Amanda H. Klein
Keyword(s):  
Locomotor Activity ◽  
Katp Channels ◽  
Opioid Administration

Evaluation of E-Cadherin and β-Catenin Immunoreactivity for Determining Undifferentiated Cells in Anaplastic Thyroid Carcinoma

Pathobiology ◽  
2021 ◽  
pp. 1-8
Author(s):  
Risa Kanematsu ◽  
Mitsuyoshi Hirokawa ◽  
Aki Tanaka ◽  
Ayana Suzuki ◽  
Miyoko Higuchi ◽  
...  
Keyword(s):  
Cell Membrane ◽  
Thyroid Carcinoma ◽  
Undifferentiated Carcinoma ◽  
Anaplastic Thyroid Carcinoma ◽  
Carcinoma Cells ◽  
Membrane Expression ◽  
Thyroid Carcinomas ◽  
Nuclear Expression ◽  
Thyroid Transcription Factor 1 ◽  
E Cadherin

<b><i>Introduction:</i></b> An immunohistochemical study has occasionally been performed to diagnose anaplastic thyroid carcinoma (ATC). However, antibodies to confirm the undifferentiated nature of ATC have not yet been evaluated. The aim of this study was to evaluate E-cadherin and β-catenin expressions in immunoreactivity to determine undifferentiated carcinoma cells in the diagnosis of ATC. <b><i>Methods:</i></b> We immunohistochemically examined 29 ATCs, 30 poorly differentiated thyroid carcinomas (PDTCs), 22 well-differentiated thyroid carcinomas (WDTCs), and 3 squamous cell carcinomas. Antibodies for thyroid transcription factor-1 (TTF-1), paired-box gene 8 (PAX8), β-catenin, and E-cadherin were used. <b><i>Results:</i></b> All WDTCs tested positive for TTF-1, PAX8, and E-cadherin. The positive rates of TTF-1, PAX8, and E-cadherin were 93.3, 93.3, and 100%, respectively, in PDTCs and 17.2, 51.7, and 10.3%, respectively, in ATCs. WDTC expressed the lateral cell membrane staining for β-catenin and E-cadherin, whereas PDTC showed circumferential cell membranous expression (fishnet pattern). β-catenin cell membrane expression in ATCs is lost or discontinuous. Carcinoma cells with β-catenin nuclear expression without cell membranous expression were scattered in 72.4% of ATCs but were not observed in the other carcinomas. <b><i>Conclusion:</i></b> We propose 3 immunohistochemical findings to determine undifferentiated carcinoma cells in the diagnosis of ATC: (1) β-catenin nuclear expression with no or reduced cell membranous expression, (2) the loss or discontinuous pattern of E-cadherin expression, and (3) the loss of PAX8 nuclear expression.

scholarly journals Lentiviral CRISPR-guided RNA library screening identified Adam17 as an upstream negative regulator of Procr in mammary epithelium

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Ting Wu ◽  
Yinghua Wang ◽  
Tianxiong Xiao ◽  
Yirui Ai ◽  
Jinsong Li ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Membrane Proteins ◽  
Epithelial Cells ◽  
Adult Stem Cells ◽  
Vascular System ◽  
Negative Regulator ◽  
Breast Cancer Cell Lines ◽  
Screening System ◽  
Membrane Expression ◽  
Sorting Technique

Abstract Background Protein C receptor (Procr) has recently been shown to mark resident adult stem cells in the mammary gland, vascular system, and pancreatic islets. More so, high Procr expression was also detected and used as indicator for subsets of triple-negative breast cancers (TNBCs). Previous study has revealed Procr as a target of Wnt/β-catenin signaling; however, direct upstream regulatory mechanism of Procr remains unknown. To comprehend the molecular role of Procr during physiology and pathology, elucidating the upstream effectors of Procr is necessary. Here, we provide a system for screening negative regulators of Procr, which could be adapted for broad molecular analysis on membrane proteins. Results We established a screening system which combines CRISPR-Cas9 guided gene disruption with fluorescence activated cell sorting technique (FACS). CommaDβ (murine epithelial cells line) was used for the initial Procr upstream effector screening using lentiviral CRISPR-gRNA library. Shortlisted genes were further validated through individual lentiviral gRNA infection followed by Procr expression evaluation. Adam17 was identified as a specific negative inhibitor of Procr expression. In addition, MDA-MB-231 cells and Hs578T cells (human breast cancer cell lines) were used to verify the conserved regulation of ADAM17 over PROCR expression. Conclusion We established an efficient CRISPR-Cas9/FACS screening system, which identifies the regulators of membrane proteins. Through this system, we identified Adam17 as the negative regulator of Procr membrane expression both in mammary epithelial cells and breast cancer cells.

scholarly journals Glycoproteomics identifies HOMER3 as a potentially targetable biomarker triggered by hypoxia and glucose deprivation in bladder cancer

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Andreia Peixoto ◽  
Dylan Ferreira ◽  
Rita Azevedo ◽  
Rui Freitas ◽  
Elisabete Fernandes ◽  
...  
Keyword(s):  
Bladder Cancer ◽  
Cell Surface ◽  
Protein Identification ◽  
Glucose Deprivation ◽  
Invasive Bladder Cancer ◽  
Nutrient Deprivation ◽  
Molecular Heterogeneity ◽  
Cell Models ◽  
Membrane Expression ◽  
Bladder Tumours

Abstract Background Muscle invasive bladder cancer (MIBC) remains amongst the deadliest genitourinary malignancies due to treatment failure and extensive molecular heterogeneity, delaying effective targeted therapeutics. Hypoxia and nutrient deprivation, oversialylation and O-glycans shortening are salient features of aggressive tumours, creating cell surface glycoproteome fingerprints with theranostics potential. Methods A glycomics guided glycoproteomics workflow was employed to identify potentially targetable biomarkers using invasive bladder cancer cell models. The 5637 and T24 cells O-glycome was characterized by mass spectrometry (MS), and the obtained information was used to guide glycoproteomics experiments, combining sialidase, lectin affinity and bottom-up protein identification by nanoLC-ESI-MS/MS. Data was curated by a bioinformatics approach developed in-house, sorting clinically relevant molecular signatures based on Human Protein Atlas insights. Top-ranked targets and glycoforms were validated in cell models, bladder tumours and metastases by MS and immunoassays. Cells grown under hypoxia and glucose deprivation disclosed the contribution of tumour microenvironment to the expression of relevant biomarkers. Cancer-specificity was validated in healthy tissues by immunohistochemistry and MS in 20 types of tissues/cells of different individuals. Results Sialylated T (ST) antigens were found to be the most abundant glycans in cell lines and over 900 glycoproteins were identified potentially carrying these glycans. HOMER3, typically a cytosolic protein, emerged as a top-ranked targetable glycoprotein at the cell surface carrying short-chain O-glycans. Plasma membrane HOMER3 was observed in more aggressive primary tumours and distant metastases, being an independent predictor of worst prognosis. This phenotype was triggered by nutrient deprivation and concomitant to increased cellular invasion. T24 HOMER3 knockdown significantly decreased proliferation and, to some extent, invasion in normoxia and hypoxia; whereas HOMER3 knock-in increased its membrane expression, which was more pronounced under glucose deprivation. HOMER3 overexpression was associated with increased cell proliferation in normoxia and potentiated invasion under hypoxia. Finally, the mapping of HOMER3-glycosites by EThcD-MS/MS in bladder tumours revealed potentially targetable domains not detected in healthy tissues. Conclusion HOMER3-glycoforms allow the identification of patients’ subsets facing worst prognosis, holding potential to address more aggressive hypoxic cells with limited off-target effects. The molecular rationale for identifying novel bladder cancer molecular targets has been established. Graphical abstract

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