Demonstration of a Direct Interaction between σ-1 Receptors and Acid-Sensing Ion Channels

Carnally, Stewart M.; Johannessen, Molly; Henderson, Ronald W.; Jackson, Meyer B.; Edwardson, J. Michael

doi:10.1016/j.bpj.2009.12.4293

Cited by 65 publications

(65 citation statements)

References 35 publications

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“…We suggest that these triplets are trimers-of-trimers that have settled onto the mica substrate and then fallen apart into individual trimers. Similar structures have been seen previously in our analysis of the structure of ASIC1a, which is also known to assemble as a trimer (29,30).…”

Section: Resultssupporting

confidence: 88%

Atomic Force Microscopy Reveals the Architecture of the Epithelial Sodium Channel (ENaC)

Stewart

Haerteis

Diakov

et al. 2011

Journal of Biological Chemistry

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The epithelial sodium channel (ENaC) is a member of the ENaC/degenerin superfamily. ENaC is a heteromultimer containing three homologous subunits (␣, ␤, and ␥); however, the subunit stoichiometry is still controversial. Here, we addressed this issue using atomic force microscopy imaging of complexes between isolated ENaC and antibodies/Fab fragments directed against specific epitope tags on the ␣-, ␤-and ␥-subunits. We show that for ␣-, ␤-and ␥-ENaC alone, pairs of antibodies decorate the channel at an angle of 120°, indicating that the individual subunits assemble as homotrimers. A similar approach demonstrates that ␣␤␥-ENaC assembles as a heterotrimer containing one copy of each subunit. Intriguingly, all four subunit combinations also produce higher-order structures containing two or three individual trimers. The trimer-of-trimers organization would account for earlier reports that ENaC contains eight to nine subunits.The epithelial sodium channel (ENaC) 5 is a member of the ENaC/degenerin superfamily, which also includes acid-sensing ion channels (ASICs; reviewed in Ref. 1). ENaC mediates Na ϩ entry across the apical membranes of many absorptive epithelia, including the alveolar epithelium, salivary duct, distal colon, and sweat glands. ENaC plays a particularly important role in Na ϩ transport across the aldosterone-sensitive distal nephron (reviewed in Ref. 2), which is responsible for the regulation of Na ϩ and K ϩ excretion, and thus plays an important role in the control of blood pressure. ENaC is the target of potassiumsparing diuretics such as amiloride and spironolactone used in the treatment of cardiovascular disease. Whereas amiloride is a direct blocker of the channel, the mineralocorticoid receptor antagonist spironolactone inhibits ENaC activity by preventing its stimulation by aldosterone.ENaC is a heteromultimer containing three homologous subunits (␣, ␤, and ␥), which have 30 -40% amino acid identity (3, 4). A fourth ENaC subunit, ␦-ENaC, has been cloned from a human kidney library (5). In heterologous expression systems, ␦-ENaC has functional similarities with ␣-ENaC, but its physiological role is still unclear (6). Each ENaC subunit contains two transmembrane domains, a large extracellular loop, and short intracellular N and C termini. Full ENaC activity requires coexpression of all three subunits (4). In the past, it has been proposed that ENaC is assembled from either four (7-9) or eight to nine subunits (10, 11). However, the recently published crystal structure of ASIC 1a (12) suggests that ENaC is likely to be a trimer (13), although this has not been demonstrated.We have developed a method, based on AFM imaging, for determining the stoichiometry and arrangement of subunits within multimeric proteins (reviewed in Ref. 14). The method involves engineering specific epitope tags onto each protein subunit and expressing the proteins exogenously in a suitable cell line (usually tsA 201). Membrane fractions from the transfected cells are solubilized in detergent, and the proteins are isola...

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Section: Resultssupporting

confidence: 88%

Atomic Force Microscopy Reveals the Architecture of the Epithelial Sodium Channel (ENaC)

Stewart

Haerteis

Diakov

et al. 2011

Journal of Biological Chemistry

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“…4). In agreement with these general ideas, using atomic force microscopy, Balasuriya et al (2012) have shown that the monomer form of the S1R (or possibly a monomer form generated from the dimer) has been identified as directly bound to the voltage-gated Na v 1.5 sodium channel with 4-fold symmetry, to the human ether-à-go-go (hERG) voltage-gated potassium channel (Balasuriya et al, 2014) with 4-fold symmetry, to the acid-sensing ion channel-1a with 3-fold symmetry (Carnally et al, 2010), and with selectivity to the GLuN1 subunit of the GluN1/GluN2a N-methyl-D-apartate receptor (Balasuriya et al, 2013) (see Table 3 for further examples of client proteins that have been shown to interact with the S1R).…”

Section: Biochemical Pharmacology Of the Sigma-1 Receptormentioning

confidence: 99%

Biochemical Pharmacology of the Sigma-1 Receptor

2015

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The sigma-1 receptor (S1R) is a 223 amino acid two transmembrane (TM) pass protein. It is a non-ATP-binding nonglycosylated ligand-regulated molecular chaperone of unknown three-dimensional structure. The S1R is resident to eukaryotic mitochondrial-associated endoplasmic reticulum and plasma membranes with broad functions that regulate cellular calcium homeostasis and reduce oxidative stress. Several multitasking functions of the S1R are underwritten by chaperone-mediated direct (and indirect) interactions with ion channels, G-protein coupled receptors and cell-signaling molecules involved in the regulation of cell growth. The S1R is a promising drug target for the treatment of several neurodegenerative diseases related to cellular stress. In vitro and in vivo functional and molecular characteristics of the S1R and its interactions with endogenous and synthetic small molecules have been discovered by the use of pharmacologic, biochemical, biophysical, and molecular biology approaches. The S1R exists in monomer, dimer, tetramer, hexamer/octamer, and higher oligomeric forms that may be important determinants in defining the pharmacology and mechanism(s) of action of the S1R. A canonical GXXXG in putative TM2 is important for S1R oligomerization. The ligand-binding regions of S1R have been identified and include portions of TM2 and the TM proximal regions of the C terminus. Some client protein chaperone functions and interactions with the cochaperone 78-kDa glucose-regulated protein (binding immunoglobulin protein) involve the C terminus. Based on its biochemical features and mechanisms of chaperone action the possibility that the S1R is a member of the small heat shock protein family is discussed.

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“…[13][14][15][16]. Sig1R functionally interacts with ion channels from various families, including voltage-dependent channels (17)(18)(19), volume-regulated chloride channels, acid-sensing ion channels (20), and Nmethyl-D-aspartic acid receptor (NMDA; refs. 21,22).…”

Section: Introductionmentioning

confidence: 99%

SIGMAR1 Regulates Membrane Electrical Activity in Response to Extracellular Matrix Stimulation to Drive Cancer Cell Invasiveness

et al. 2016

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The sigma 1 receptor (Sig1R) is a stress-activated chaperone that regulates ion channels and is associated with pathologic conditions, such as stroke, neurodegenerative diseases, and addiction. Aberrant expression levels of ion channels and Sig1R have been detected in tumors and cancer cells, such as myeloid leukemia and colorectal cancer, but the link between ion channel regulation and Sig1R overexpression during malignancy has not been established. In this study, we found that Sig1R dynamically controls the membrane expression of the human voltage-dependent K þ channel human ether-a-go-go-related gene (hERG) in myeloid leukemia and colorectal cancer cell lines. Sig1R promoted the formation of hERG/b1-integrin signaling complexes upon extracellular matrix stimulation, triggering the activation of the PI3K/ AKT pathway. Consequently, the presence of Sig1R in cancer cells increased motility and VEGF secretion. In vivo, Sig1R expression enhanced the aggressiveness of tumor cells by potentiating invasion and angiogenesis, leading to poor survival. Collectively, our findings highlight a novel function for Sig1R in mediating crosstalk between cancer cells and their microenvironment, thus driving oncogenesis by shaping cellular electrical activity in response to extracellular signals. Given the involvement of ion channels in promoting several hallmarks of cancer, our study also offers a potential strategy to therapeutically target ion channel function through Sig1R inhibition. Cancer Res; 76(3); 607-18. Ó2015 AACR.

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Demonstration of a Direct Interaction between σ-1 Receptors and Acid-Sensing Ion Channels

Cited by 65 publications

References 35 publications

Atomic Force Microscopy Reveals the Architecture of the Epithelial Sodium Channel (ENaC)

Atomic Force Microscopy Reveals the Architecture of the Epithelial Sodium Channel (ENaC)

Biochemical Pharmacology of the Sigma-1 Receptor

SIGMAR1 Regulates Membrane Electrical Activity in Response to Extracellular Matrix Stimulation to Drive Cancer Cell Invasiveness

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