Satomi Matsuoka

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Sodium-calcium exchange current was isolated in inside-out patches excised from guinea pig ventricular cells using the giant patch method. The outward exchange current decayed exponentially upon activation by cytoplasmic sodium (sodium-dependent inactivation). The kinetics and mechanism of the inactivation were studied. (a) The rate of inactivation and the(More)
Dynamic responses of cardiac sodium-calcium exchange current to changes of cytoplasmic calcium and MgATP were monitored and analyzed in giant membrane patches excised from guinea pig myocytes. Secondary dependencies of exchange current on cytoplasmic calcium are accounted for in terms of two mechanisms: (a) The sodium-dependent inactivation process, termed(More)
To investigate the regulation of native cardiac Na+-Ca2+ exchange by cytoplasmic Na+ (Na+i) and Ca2+ (Ca2+i), we recorded the Na+-Ca2+ exchange current (INa-Ca) from inside-out 'macro patches' excised from intact guinea-pig ventricular cells. The half-maximal concentration (Kh) of Ca2+i required to induce an inward INa-Ca was 7 microM. The Kh of Na+i(More)
The Na(+)-Ca2+ exchanger is an important regulator of cellular Ca2+ levels, and one isoform of this transporter, NCX1, has been cloned previously (Nicoll, D.A., Longoni, S., and Philipson, K.D. (1990) Science 250, 562-565). We now report the cloning of a second isoform (NCX2) of the Na(+)-Ca2+ exchanger which was present in a rat brain cDNA library. NCX2 is(More)
The sarcolemmal Na(+)-Ca2+ exchanger is regulated by intracellular Ca2+ at a high affinity Ca2+ binding site separate from the Ca2+ transport site. Previous data have suggested that the Ca2+ regulatory site is located on the large intracellular loop of the Na(+)-Ca2+ exchange protein, and we have identified a high-affinity 45Ca2+ binding domain on this loop(More)
The Na(+)-Ca2+ exchanger from Drosophila was expressed in Xenopus and characterized electrophysiologically using the giant excised patch technique. This protein, termed Calx, shares 49% amino acid identity to the canine cardiac Na(+)-Ca2+ exchanger, NCX1. Calx exhibits properties similar to previously characterized Na(+)-Ca2+ exchangers including(More)
We have analyzed the regulatory properties of the wild-type cardiac Na(+)-Ca2+ exchanger expressed in Xenopus laevis oocytes using the giant excised patch technique. The exchanger is activated by cytoplasmic application of chymotrypsin and exhibits a number of properties that can be changed or abolished by chymotrypsin treatment, including cytoplasmic(More)
1. To identify the Na+- or Ca2+-induced current as Na+-Ca2+ exchange current and to determine the stoichiometry of the Na+-Ca2+ exchange, the reversal potential was measured in a wide range of external Na+ [( Na+]o) or Ca2+ [( Ca2+]o) concentrations. The Na+- or Ca2+-induced current was recorded in single ventricular cells enzymatically dispersed from(More)
We have examined the role of conserved regions and acidic or basic residues located in the putative transmembrane segments of the cardiac sarcolemmal Na+-Ca2+ exchanger by site-directed mutagenesis. The alpha-1 and alpha-2 repeats are transmembrane regions of internal similarity, which are highly conserved among Na+-Ca2+ exchangers. We find that Na+-Ca2+(More)
4F2, also termed CD98, is an integral membrane protein consisting of a heavy chain linked to a light chain by disulfide bond. We have generated a monoclonal antibody to the mouse 4F2 light chain and cloned the cDNA. It encodes a mouse counterpart of rat L-type amino acid transporter-1, and induces system L amino acid transport in Xenopus oocytes in the(More)