Rab coupling protein (RCP): a novel target of progesterone action in primate endometrium

Abstract

Acquisition of functional receptivity by the endometrium is assumed to be effected by progesterone-dependent expression and repression of several genes during the implantation window in a menstrual cycle. In the present study, we employed differential display (DD) reverse transcription-polymerase chain reaction (RT-PCR) to identify progesterone-dependent gene/gene fragments that are differentially expressed during the peri-implantation phase in receptive and nonreceptive endometria, obtained from fertile and infertile bonnet monkeys respectively. Receptive endometria were obtained from regularly cycling (n=5) fertile female bonnet monkeys. Endometrial nonreceptivity was induced by treating bonnet monkeys with either 2·5 mg (n=5) or 5·0 mg (n=5) onapristone (ZK 98·299), an antiprogestin, on every third day for one cycle. Ovulation, levels of circulatory hormones (estradiol and progesterone) and menstrual cycle length did not change in treated animals; however, endometrial growth was retarded. DD2, one of the differentially expressed cDNA fragments, showed higher representation in nonreceptive endometria than in receptive endometria. The DD2 sequence was found to be homologous to the sequence of the carboxyl terminal region of Rab coupling protein (RCP), a recently discovered protein involved in intracellular vesicular trafficking. To confirm the identity of DD2 as RCP, RT-PCR studies were carried out with a forward primer deduced from the RCP sequence and a reverse primer from the DD2 sequence. The product (DDRCP) obtained, when sequenced, revealed 95% homology with the nucleotide number 1196-1757 of human RCP cDNA. Furthermore, the pattern of DDRCP expression at transcript level was found to be similar to that shown by DD2; that is, it was higher in nonreceptive endometrium. Northern analysis using labeled DD2 or DDRCP cDNA fragments identified two transcripts of 6·0 and 4·0 kb in human endometrium. In situ hybridization studies using digoxigenin-labeled DD2 revealed significantly higher (P,0·05) localization of endometrial RCP transcripts in the proliferative phase than in the peri-implantation phase in control animals. The localization was also significantly (P,0·01) higher in peri-implantation-phase endometria from antiprogestin-treated animals than in control animals. These antiprogestin-treated animals, however, did not demonstrate any concomitant increase in the levels of immunoreactive endometrial Rab4 and Rab11 during the peri-implantation phase. A similar pattern of cycle-dependent RCP expression was observed in human endometrial biopsies. Furthermore, significantly higher (P,0·05) levels of RCP transcripts were detected during the periimplantation phase in women with unexplained infertility (n=3) than in fertile women (n=3). This is the first report indicating the endometrial expression of RCP and its hormonal regulation.

Regulation of homeobox A10 expression in the primate endometrium by progesterone and embryonic stimuli

“…To investigate whether HOXA10 is under the regulation of progesterone in primate endometrium, its expression was studied in the endometria of animals treated with onapristone. We have earlier shown that onapristone, at the specified doses in bonnet monkey, does not affect the hypothalamus-pituitary-ovarian axis but blocks implantation in the bonnets (Katkam et al 1995) and the expression of some progesterone-regulated genes is also altered (Puri et al 2000, Sachdeva et al 2001, Patil et al 2005. In the present study, we found that blocking progesterone actions (by onapristone treatment) lead to suppression of HOXA10 mRNA and protein expression in the endometrium.…”

The dynamic Rab11-FIPs

“…Indeed, it is now clear that the FIPs are critical regulators of multiple endosomal-recycling processes (Figure 2). They have also been shown to function in several crucial cellular physiological processes such as cell division, cell migration, responses to insulin, memory processes, immune and inflammatory responses, water reabsorption, fertility, retinal cell development and various human cancers [16,24,27,28,[32][33][34][35][36][37][47][48][49][50]. This repertoire of FIP functions is everexpanding and as many of these cellular processes are disease associated, it identifies the FIPs as potential targets for therapeutic intervention in the treatment of human diseases in the future.…”

Developmental expression and cellular distribution of Müllerian inhibiting substance in the primate ovary

“…The cyclicity and the hormonal profiles of the animals have been reported previously (Patil et al 2005).…”