By fluorescence-activated cell sorting (FACS) analysis, Fukudome and Esmon (1994) determined that activated protein C
(APC) specifically binds to cultured endothelial cells in a calcium-dependent manner that is not influenced by protein S
. The authors screened an endothelial cell library for APC-binding partners and isolated a cDNA
encoding PROCR, which they termed EPCR. Sequence analysis predicted that the 238-amino acid type 1 transmembrane
protein has a 15-amino acid N-terminal signal sequence; an extracellular domain with 4 potential N-glycosylation sites and
4 cys residues; a C-terminal 25-amino acid transmembrane region; and a short cytoplasmic tail containing only 3 amino
acids.
NCBI Summary:
The protein encoded by this gene is a receptor for activated protein C, a serine protease activated by and involved in the blood coagulation pathway. The encoded protein is an N-glycosylated type I membrane protein that enhances the activation of protein C. Mutations in this gene have been associated with venous thromboembolism and myocardial infarction, as well as with late fetal loss during pregnancy.
General function
Receptor
Comment
Cellular localization
Plasma membrane
Comment
Ovarian function
Steroid metabolism, Luteinization
Comment
Intraovarian Thrombin and Activated Protein C Signaling System Regulates Steroidogenesis during the Periovulatory Period. Cheng Y et al. In addition to its role in blood coagulation, thrombin directly stimulates protease-activated receptors (PAR) or interacts with thrombomodulin (THBD) to activate membrane-bound protein C which stimulates PAR1 and PAR4 receptors to promote downstream pleiotropic effects. Our DNA microarray, RT-PCR, and immunostaining analyses demonstrated ovarian expression of THBD, activated protein C (APC) receptor [endothelial protein C receptor (EPCR)], as well as PAR1 and PAR4 receptors in mice. After treatment of gonadotropin-primed immature mice with an ovulatory dose of human chorionic gonadotropin (hCG) (a LH surrogate), major increases in the expression of THBD, EPCR, PAR1, and PAR4 were detected in granulosa and cumulus cells of preovulatory follicles. Immunoassay analyses demonstrated sustained increases in ovarian prothrombin and APC levels after hCG stimulation. We obtained luteinizing granulosa cells from mice treated sequentially with equine CG and hCG. Treatment of these cells with thrombin or agonists for PAR1 or PAR4 decreased basal and forskolin-induced cAMP biosynthesis and suppressed hCG-stimulated progesterone production. In cultured preovulatory follicles, treatment with hirudin (a thrombin antagonist) and SCH79797 (a PAR1 antagonist) augmented hCG-stimulated progesterone biosynthesis, suggesting a suppressive role of endogenous thrombin in steroidogenesis. Furthermore, intrabursal injection with hirudin or SCH79797 led to ipsilateral increases in ovarian progesterone content. Our findings demonstrated increased ovarian expression of key components of the thrombin-APC-PAR1/4 signaling system after LH/hCG stimulation, and this signaling pathway may allow optimal luteinization of preovulatory follicles. In addition to assessing the role of thrombin and associated genes in progesterone production by the periovulatory ovary, these findings provide a model with which to study molecular mechanisms underlying thrombin-APC-PAR1/4 signaling.
Expression regulated by
LH
Comment
Ovarian localization
Oocyte, Granulosa
Comment
Genomewide discovery and classification of candidate ovarian fertility genes in the mouse. Gallardo TD et al. Female infertility syndromes are among the most prevalent chronic health disorders in women, but their genetic basis remains unknown because of uncertainty regarding the number and identity of ovarian factors controlling the assembly, preservation, and maturation of ovarian follicles. To systematically discover ovarian fertility genes en masse, we employed a mouse model (Foxo3) in which follicles are assembled normally but then undergo synchronous activation. We developed a microarray-based approach for the systematic discovery of tissue-specific genes and, by applying it to Foxo3 ovaries and other samples, defined a surprisingly large set of ovarian factors (n = 348, approximately 1% of the mouse genome). This set included the vast majority of known ovarian factors, 44% of which when mutated produce female sterility phenotypes, but most were novel. Comparative profiling of other tissues, including microdissected oocytes and somatic cells, revealed distinct gene classes and provided new insights into oogenesis and ovarian function, demonstrating the utility of our approach for tissue-specific gene discovery. This study will thus facilitate comprehensive analyses of follicle development, ovarian function, and female infertility. This is an oocyte and cumulus cell-specific gene.