Gestodene, a Positive Allosteric Modulator of PAR1, Enhances PAR1-Mediated Morphological Changes in MEG-01 Cells

Protease-activated receptor 1 (PAR1) is a high-affinity thrombin receptor expressed in human platelets and can be activated by low levels of thrombin. Selective inhibition of PAR1 by vorapaxar significantly inhibits thrombin-induced calcium mobilization in human platelets and increases the risk of bleeding, suggesting that positive allosteric modulator (PAM) of PAR1 may increase the risk of thrombosis. In the present study, we performed a cell-based screening to identify novel PAMs of PAR1 and found gestodene, which acts as PAM of PAR1. Gestodene enhanced both thrombin- and PAR1-AP-induced increases in intracellular calcium levels through PAR1 in a dose-dependent manner, but it did not alter the activity of PAR2 and PAR4. Gestodene increased PAR1-AP-induced internalization of PAR1 receptors and phosphorylation of ERK1/2, and the enhancing effects were significantly blocked by vorapaxar. Furthermore, gestodene potently increased PAR1-AP-induced morphological changes in the human megakaryoblastic leukemia cell line MEG-01 cells, a cellular model of PAR1-mediated morphological changes in platelets. Our results reveal that gestodene is a selective PAM of PAR1 and provide a molecular basis for the risk of venous thromboembolism induced by oral contraceptives including gestodene. This research was supported by a Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2018R1A6A1A03023718). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.