Modulation of human myometrial PGE2 receptor by GTP characterization of receptor subtype

EP4 receptor agonist CAY10598 upregulates ROS-dependent Hsp90 cleavage in colorectal cancer cells

Prostaglandin E2 (PGE2) interacts with four specific G protein-coupled receptors, namely EP1, EP2, EP3, and EP4, playing a pivotal role in determining the fate of cells. Our previous findings highlighted that stimulating the EP4 receptor with its agonist, CAY10598, triggers apoptosis in colon cancer HCT116 cells via the production of reactive oxygen species (ROS). This process also reduces the phosphorylation of the oncogenic protein JAK2 and leads to its degradation in these cells. In this study, our goal was to explore the pathways through which CAY10598 leads to JAK2 degradation. We focused on Hsp90, a heat shock protein family member known for its role as a molecular chaperone maintaining the stability of several key proteins including EGFR, MET, Akt, and JAK2. Our results show that CAY10598 decreases the levels of client proteins of Hsp90 in HCT116 cells, an effect reversible by pretreatment with the ROS scavenger N-acetyl cysteine (NAC) or the proteasome inhibitor MG132, indicating that the degradation is likely driven by ROS. Furthermore, we observed that CAY10598 cleaves both α and β isoforms of Hsp90, the process inhibited by NAC. Inhibition of EP4 with the antagonist GW627368x not only prevented the degradation of Hsp90 client proteins but also the cleavage of Hsp90 itself in CAY10598-treated HCT116 cells. Additionally, CAY10598 suppressed the growth of HCT116 cells implanted in mice. Our findings reveal that CAY10598 induces apoptosis in cancer cells by a novel mechanism involving the ROS-dependent cleavage of Hsp90, thereby inhibiting the function of crucial Hsp90 client proteins.

Crystal structure of misoprostol bound to the labor inducer prostaglandin E2 receptor

Misoprostol is a life-saving drug in many developing countries for women at risk of post-partum hemorrhaging owing to its affordability, stability, ease of administration and clinical efficacy. However, misoprostol lacks receptor and tissue selectivities, and thus its use is accompanied by a number of serious side effects. The development of pharmacological agents combining the advantages of misoprostol with improved selectivity is hindered by the absence of atomic details of misoprostol action in labor induction. Here, we present the 2.5 Å resolution crystal structure of misoprostol free-acid form bound to the myometrium labor-inducing prostaglandin E₂ receptor 3 (EP3). The active state structure reveals a completely enclosed binding pocket containing a structured water molecule that coordinates misoprostol's ring structure. Modeling of selective agonists in the EP3 structure reveals rationales for selectivity. These findings will provide the basis for the next generation of uterotonic drugs that will be suitable for administration in low resource settings.