Objective      To screen the oligonucleotide aptamers for the first extracellular domain of Orai1 protein in order to determine the inhibitory effects of aptamers on mast cells activation by Ca

2+

release activation channel (CRAC).       Methods      Random single-strand DNA (ssDNA) library was constructed. The key parameters of asymmetric PCR were optimized to amplify ssDNA library. The oligonucleotide aptamers were screened by systematic evolution o

f ligand by exponential enrichment (SELEX) technology with enzyme-linked polystyrene plate as medium. The affinity between ssDNA library and target protein was examined in each round by ELISA. The changes of intracellular Ca

2+

concentration in LAD2 mast cell line were tested by laser confocal microscopy. The β-hexosaminidase release from LAD2 cells was measured so that the aptamer effects on mast cell activation mediated by IgE could be evaluated.       Results      Seven oligonucleotide aptamers were obtained after 12 rounds of SELEX. The Kd value of Aptamer Y1 reached 1.72×10

-8

mol/L. Aptamer Y1 at the final concentration 2 μg/mL decreased the calcium entry and inhibited the β-hexosaminidase release from LAD2 cells by 95%.       Conclusion      The seven oligonucleotide aptamers targeting the first extracellular domain of Orai1 protein are obtained by SELEX technology. The aptamers can decrease intracellular calcium influx and inhibit the release of β-hexosaminidase from LAD2 cells effectively

and therefore

inhibit mast cell activation through CRAC channels.