Section 10
Chapter 9,685

Two isoforms of prostaglandin E receptor EP3 subtype. Different COOH-terminal domains determine sensitivity to agonist-induced desensitization

Negishi, M.; Sugimoto, Y.; Irie, A.; Narumiya, S.; Ichikawa, A.

Journal of Biological Chemistry 268(13): 9517-9521


ISSN/ISBN: 0021-9258
PMID: 8387497
Accession: 009684084

We recently identified two isoforms of mouse prostaglandin (PG) E receptor EP-3 subtype, EP-3alpha and EP-3beta, which are produced by alternative splicing and different only in the carboxyl-terminal domain (Sugimoto, Y., Negishi, M., Hayashi, Y., Namba, T., Honda, A., Watabe, A., Hirata, M., Narumiya, S., and Ichikawa, A. (1993) J. Biol. Chem. 268, 2712-2718). We examined here agonist-induced desensitization of the two isoforms using Chinese hamster ovary cells stably expressing these isoforms. Exposure of the EP-3alpha isoform to PGE-2 for 30 min did not change maximal response but increased PGE-2 concentration needed to inhibit forskolin-induced cAMP accumulation in the cells. Further exposure of this isoform to PGE-2 suppressed the maximal response as well as sensitivity to PGE-2 in a time-dependent manner; after 24-h exposure, it elicited only 50% of the maximal response of the control cells. Consistent with these results, short term exposure sequestered the EP-3alpha isoform away from the cell surface and long term incubation decreased the total receptor number in the cells. In contrast, exposure of the EP-3beta isoform to PGE-2 did not affect its dose-response curve for PGE-2, and no sequestration or decrease in the receptor number was observed in this isoform. Thus, alternative splicing produced the two isoforms with different carboxyl-terminal domains, which are different in sensitivity to agonist-induced desensitization.

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