Dominant negative actions of human prostacyclin receptor variant through dimerization: implications for cardiovascular disease.
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.


RESULTS
Dimerization of the IP, IP(R212C), and TPalpha was examined by bioluminesence resonance energy transfer in transfected HEK293 cells. We observed an equal propensity for formation of IPIP homodimers and IPTPalpha 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 TPalpha activation response, which was shifted from inositol phosphate to cAMP generation following IPTPalpha heterodimerization, was normalized when the TPalpha instead dimerized with IP(R212C).


CONCLUSIONS
IP(R212C) exerts a dominant action on the wild-type IP and TPalpha through dimerization. This likely contributes to accelerated cardiovascular disease in individuals carrying 1 copy of the variant allele.
Institute for Translational Medicine and Therapeutics, University of Pennsylvania, Philadelphia, PA 19104, USA.
Salam
S
Ibrahim
Mazell
M
Tetruashvily
Alex J
AJ
Frey
Stephen J
SJ
Wilson
Jeremiah
J
Stitham
John
J
Hwa
Emer M
EM
Smyth
D002318:Cardiovascular Diseases / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000378:metabolism; D011464:Epoprostenol / Q000031:analogs & derivatives / Q000494:pharmacology; D031541:Fluorescence Resonance Energy Transfer; D005838:Genotype; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D044006:Receptors, Epoprostenol; D011982:Receptors, Prostaglandin / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015290:Second Messenger Systems; D014162:Transfection
D007295:Inositol Phosphates; C113936:PTGIR protein, human; D044006:Receptors, Epoprostenol; D011982:Receptors, Prostaglandin; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D011993:Recombinant Fusion Proteins; D011464:Epoprostenol; D000242:Cyclic AMP; C043867:cicaprost