title: A truncated progesterone receptor (PR-M) localizes to the mitochondrion and controls cellular respiration.
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.
authors.affiliation: Departments of Obstetrics and Gynecology, Duke University, Durham, NC 27710, USA.
authors.forename: Qunsheng
authors.initials: Q
authors.lastname: Dai
authors.forename: Anish A
authors.initials: AA
authors.lastname: Shah
authors.forename: Rachana V
authors.initials: RV
authors.lastname: Garde
authors.forename: Bryan A
authors.initials: BA
authors.lastname: Yonish
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.forename: Neil A
authors.initials: NA
authors.lastname: Medvitz
authors.forename: Sara E
authors.initials: SE
authors.lastname: Miller
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Hansen
authors.forename: Carrie N
authors.initials: CN
authors.lastname: Dunn
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Price
mesh_terms: D020029:Base Pairing / Q000235:genetics; D015152:Blotting, Northern; D045744:Cell Line, Tumor; D019069:Cell Respiration / Q000187:drug effects; D005260:Female; D006801:Humans; D013058:Mass Spectrometry; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D051336:Mitochondrial Membranes / Q000378:metabolism / Q000648:ultrastructure; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D011372:Progestins / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011980:Receptors, Progesterone / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D024101:Mitochondrial Proteins; C585679:PR-M protein, human; D010455:Peptides; D011372:Progestins; D012333:RNA, Messenger; D011980:Receptors, Progesterone; D010100:Oxygen