Browsing by Author "Torry, Lisa"

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    Alternative splicing of NCX1 affects the sensitivity of its Ca2+ sensors
    (2012-10-01) Torry, Lisa; Lytton, Jonathan
    The Na+/Ca2+ exchanger, NCX1, is important for Ca2+ homeostasis in many different tissues. Exchange function is regulated by Ca2+ binding to two cytoplasmic domains, CBD1 and CBD2, that are subject to tissue-specific alternative splicing. To test if alternative splicing modulates Ca2+ binding to the CBDs, the isolated domains CBD1, CBD2, and the tandem construct CBD12 from different NCX1 spliced isoforms were produced, purified and analyzed for Ca2+ binding in a competition binding assay using fluorescent Ca2+ indicators. NCX1.4-CBD2 bound two Ca2+ ions while NCX1.3-CBD2 did not bind Ca2+. CBD1 bound four Ca2+ ions, and some of the CBD1 Ca2+ binding sites in the CBD12 tandem construct had isoform-specific affinities significantly higher than CBD1 alone. My results confirm that alternative splicing of NCX1 affects regulatory Ca2+ binding in both CBDs, and thus tailors NCX1 function to suit tissue-specific requirements for Ca2+ homeostasis.