Molecular Cloning and Characterization of Bovine Prostaglandin E2 Receptors EP2 and EP4: Expression and Regulation in Endometrium and Myometrium during the Estrous Cycle and Early Pregnancy

Abstract

Prostaglandins (PGs) play important functions in the reproductive system, and PGE(2) appears necessary for recognition of pregnancy. We have found that PGE(2) is able to increase cAMP generation in the bovine endometrium. There are two PGE(2) receptors (EP), EP2 and EP4, that are coupled to adenylate cyclase to generate cAMP, but these receptors have not been studied in the bovine. We have cloned and characterized bovine EP2 and EP4 receptors and studied their expression in the uterus. The amino acid sequences of bovine EP2 and EP4 possess a high degree (>80%) of identity with the other mammalian homologs. EP2 is expressed in most tissues, and EP4 is expressed only in intestine and testis. EP2 mRNA and protein are expressed in endometrium and myometrium during the estrous cycle, whereas EP4 is undetectable. The Western analysis indicates that EP2 is maximally expressed in both endometrium and myometrium between d 10 and 18 of the estrous cycle. Immunohistochemical localization reveals that EP2 protein is expressed in all cell types of endometrium and myometrium. On d 18, pregnancy up-regulates EP2 protein, primarily in endometrial stroma and myometrial smooth muscle cells. In conclusion, EP2 is the major cAMP-generating PGE(2) receptor expressed and regulated in the bovine uterus during the estrous cycle and early pregnancy.

Prostaglandin E2 Inhibits Alveolar Macrophage Phagocytosis through an E-Prostanoid 2 Receptor-Mediated Increase in Intracellular Cyclic AMP

“…The apparent mobilities for the EP2 and EP3 receptors (ϳ68 kDa and ϳ62 kDa, respectively) were different from the theoretical molecular masses predicted from the primary amino acid sequences (40 kDa and 40 -45 kDa, respectively) (22,54). This discrepancy between predicted and apparent molecular masses by SDS-PAGE has been reported previously with membrane receptors, including rat, bovine, and human EP receptors (55)(56)(57), and may result from receptor oligomerization (58) or posttranslational modifications such as glycosylation and/or phosphorylation (55,56). In agreement with our results, apparent mobilities of 68 and 62 kDa have also been reported for the human EP2 and EP3 receptors (55).…”

The Prostanoid EP4 Receptor and Its Signaling Pathway

“…Moderate expression of EP4 was demonstrated in the human , bovine (Arosh et al, 2003), and chicken (Kwok et al, 2008) testis, although no EP4 expression was detectable in the mouse or rat (Sando et al, 1994) testis.…”

“…In female reproductive organs such as the ovary and uterus, hormonal exposure induces expression of the EP subtypes in a cell type-specific manner. EP4 is expressed in the mouse ovary (Segi et al, 2003) and in the human (Milne et al, 2001;Astle et al, 2005), baboon , mouse Yang et al, 1997), rat (Blesson et al, 2012), and guinea pig (Terry et al, 2008) uterus, although Arosh et al (2003Arosh et al ( , 2004 reported that EP4 mRNA was undetectable in the bovine uterus.…”

Transcriptomic Analysis of the Bovine Endometrium: What is Required to Establish Uterine Receptivity to Implantation in Cattle ?

“…Gene expression is given in italics and protein abundance is given in normal font. Data compiled from references [20,27,34,35,49,64,65,67,[74][75][76][77]. FORDE and LONERGAN 192 in both beef and dairy cattle have identified a correlation between concentrations of progesterone up to Day 7 following insemination and subsequent pregnancy rates [44,45].…”

“…those that encoded for growth factors/ cytokines or those involved in the progression of the estrous cycle. The expression of insulin-like growth factor 2; IGFII, insulin-like growth factor binding protein 2, 36 kDa; IGFBP2 [48], prostaglandin E receptor 2 (subtype EP2), 53 kDa; PTGER2 [49], vascular endothelial growth factor receptor 2; VEGFR2 [50] in the endometrium, increases during the elongation stage of conceptus development while the expression of ESR1 [51], matrix metallopeptidase 2 (gelatinase A, 72 kDa type IV collagenase; MMP2 [52], and VEGF [50] declines. Treatment with exogenous progesterone increased the expression of uterine serpins [53] as well as PGR, ESR1 and retinol binding protein 4, plasma; RBP4 [54].…”