ABSTRACT
The cDNA for a novel truncated progesterone receptor (PR-M) was previously cloned from human adipose and aortic cDNA libraries. The predicted protein sequence contains 16 unique N-terminal amino acids, encoded by a sequence in the distal third intron of the progesterone receptor PR gene, followed by the same amino acid sequence encoded by exons 4 through 8 of the nuclear PR. Thus, PR-M lacks the N terminus A/B domains and the C domain for DNA binding, whereas containing the hinge and hormone-binding domains. In this report, we have localized PR-M to mitochondria using immunofluorescent localization of a PR-M-green fluorescent protein (GFP) fusion protein and in Western blot analyses of purified human heart mitochondrial protein. Removal of the putative N-terminal mitochondrial localization signal obviated association of PR-M with mitochondria, whereas addition of the mitochondrial localization signal to green fluorescent protein resulted in mitochondrial localization. Immunoelectron microscopy and Western blot analysis after mitochondrial fractionation identified PR-M in the outer mitochondrial membrane. Antibody specificity was shown by mass spectrometry identification of a PR peptide in a mitochondrial membrane protein isolation. Cell models of overexpression and gene silencing of PR-M demonstrated a progestin-induced increase in mitochondrial membrane potential and an increase in oxygen consumption consistent with an increase in cellular respiration. This is the first example of a truncated steroid receptor, lacking a DNA-binding domain that localizes to the mitochondrion and initiates direct non-nuclear progesterone action. We hypothesize that progesterone may directly affect cellular energy production to meet the increased metabolic demands of pregnancy.
Subject(s)
Mitochondria, Heart/metabolism , Receptors, Progesterone/metabolism , Base Pairing/genetics , Blotting, Northern , Cell Line, Tumor , Cell Respiration/drug effects , Female , Humans , Mass Spectrometry , Membrane Potential, Mitochondrial/drug effects , Mitochondria, Heart/drug effects , Mitochondria, Heart/ultrastructure , Mitochondrial Membranes/metabolism , Mitochondrial Membranes/ultrastructure , Mitochondrial Proteins/chemistry , Mitochondrial Proteins/metabolism , Oxygen/metabolism , Peptides/chemistry , Peptides/metabolism , Progestins/pharmacology , Protein Transport/drug effects , RNA Interference , RNA, Messenger/genetics , RNA, Messenger/metabolism , Receptors, Progesterone/chemistry , Receptors, Progesterone/geneticsABSTRACT
OBJECTIVE: To discuss the possible role of abnormal embryo migration as a cause of ectopic pregnancy during IVF with hydrosalpinges. DESIGN: Case report. SETTING: University-based reproductive endocrinology and fertility clinic. PATIENT(S): A patient presenting with a tubal ectopic pregnancy after spontaneous conception in a preexisting hydrosalpinx. INTERVENTION(S): Laparoscopic salpingectomy. MAIN OUTCOME MEASURE(S): Ultrasound and operative findings. RESULT(S): Case demonstration of abnormal embryo migration into a surgically documented preexisting hydrosalpinx during a spontaneous conception. CONCLUSION(S): The mechanism of increased tubal ectopic pregnancy rates during IVF with hydrosalpinges remains unexplained. This case supports abnormal embryo migration due to the hydrosalpinx as a contributing factor.
