The role of alternative splicing and C-terminal amino acids in thromboxane receptor stabilization

The thromboxane receptor has two alternatively spliced isoforms, α and β, which differ only in sequences within the cytoplasmic C-terminal domain. Oxidative stress induced by H2O2 in a COS-7 cell model results in stabilization of the thromboxane receptor β isoform by translocation from the endoplasmic reticulum to the Golgi complex, which in turn results in protection of the receptor from degradation. We now report that both the α and β thromboxane receptor isoforms respond identically to oxidative stress. Further, mutagenesis studies indicate that replacing the normal C-terminus with a nonsense sequence also does not alter stabilization behaviour ruling out a role for the distinct C-termini in this process. Further mutagenesis implicates a cluster of arginine residues within the C-terminal domain as involved in oxidative stress-induced stabilization. These data identify a region of the thromboxane receptor that is responsible for responding to oxidative challenge and open the possibility of identification of the molecular machinery underpinning this response.