Identification of an alternatively spliced isoform of the common cytokine receptor gamma chain in chickens.

The common cytokine receptor gamma(gamma(c)) chain is shared by at least six cytokine receptors and plays a critical role in the regulation of immune responses. In this study, we discovered that, unlike mammals, chickens possess two different gamma(c) gene transcripts, chgamma(c)-a and chgamma(c)-b. Sequence comparisons between the cDNAs and a gamma(c) genomic clone isolated by PCR revealed that chgamma(c)-b contained an in-frame 78bp insertion between Gly-222 and Val-223 of the chgamma(c)-a sequence. This insertion most likely resulted from alternative splicing such that the fifth intron was not removed from the chgamma(c)-b transcript. Furthermore, while chgamma(c)-a and chgamma(c)-b transcripts were expressed equally in the spleen, thymus, bursa, and cecal tonsils, they were differentially expressed during the time course of Con A stimulation of splenic T lymphocytes. Western blot analysis of normal spleen lymphocytes identified 45, 53, and 64 kDa immunoreactive bands whereas only 64kDa band was detected in Con A-activated splenic lymphocytes. COS-7 cells transfected with chgamma(c)-b secreted approximately 42kDa proteins. Taken together, our results document that chickens express an alternative spliced gamma(c) receptor which is larger than the conventional transcript and this novel isoform generates soluble receptors in the transfected COS-7 cells.

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