Dominant Negative Actions of Human Prostacyclin Receptor Variant Through Dimerization: Implications for Cardiovascular Disease

Abstract

Objective— Prostacyclin and thromboxane mediate opposing cardiovascular effects through their receptors, the prostacyclin receptor (IP) and thromboxane receptor (TP). Individuals heterozygous for an IP variant, IP ^R212C , displayed exaggerated loss of platelet IP responsiveness and accelerated cardiovascular disease. We examined association of IP ^R212C into homo- and heterodimeric receptor complexes and the impact on prostacyclin and thromboxane biology. Methods and Results— Dimerization of the IP, IP ^R212C , and TPα was examined by bioluminesence resonance energy transfer in transfected HEK293 cells. We observed an equal propensity for formation of IPIP homodimers and IPTPα heterodimers. Compared with the IP alone, IP ^R212C displayed reduced cAMP generation and increased endoplasmic reticulum localization but underwent normal homo- and heterodimerization. When the IP ^R212C and IP were coexpressed, a dominant negative action of the variant was evident with enhanced wild-type IP localization to the endoplasmic reticulum and reduced agonist-dependent signaling. Further, the TPα activation response, which was shifted from inositol phosphate to cAMP generation following IPTPα heterodimerization, was normalized when the TPα instead dimerized with IP ^R212C . Conclusion— IP ^R212C exerts a dominant action on the wild-type IP and TPα through dimerization. This likely contributes to accelerated cardiovascular disease in individuals carrying 1 copy of the variant allele.