Thromboxane (TXA2) binds to the thromboxane receptor (TP). There are 2 splice variant forms of TP, differing in their cytoplasmic carboxyl terminal tails. TP beta was first identified in endothelial cells. TP alpha was identified in platelets and placenta. The major signalling route for TP is Gq-mediated stimulation of PLC and consequent increase in cellular calcium. TP also couples to G13, leading to stimulation of Rho and Rac.