title: Antiapoptotic signaling via MCL1 confers resistance to caspase-3-mediated apoptotic cell death in the pregnant human uterine myocyte.
abstract: Our group has previously identified elevated levels of nonapoptotic active caspase 3 (CASP3) accompanied by increased prosurvival, antiapoptotic signaling in the pregnant mouse uterus during late gestation. We speculated that increased antiapoptotic signaling desensitized the pregnant uterine myocyte to the apoptotic action of uterine CASP3. This current study examines the mechanism by which the pregnant myocyte gains resistance to the apoptotic effects of increased uterine CASP3. Using both primary human pregnant fundal myometrial cultures and the telomerase-immortalized human uterine myocyte cell line (hTERT) as our model systems, uterine myocytes were exposed to UV irradiation and Fas ligand to stimulate both the intrinsic and extrinsic apoptotic pathways. Stimulation of either the intrinsic or extrinsic apoptotic pathways resulted in elevated levels of uterine myocyte CASP3. However, apoptotic cell death was restricted to CASP3 activated by intrinsic stimulation via UV light. In contrast Fas ligand-mediated CASP3 activation was accompanied by increased antiapoptotic signaling mimicking our in vivo observations in the pregnant mouse uterus. Using small interfering RNA to inhibit antiapoptotic signaling, we determined the ability of the human uterine myocyte to resist apoptotic cell death in the absence of the prosurvival, antiapoptotic signaling. Accordingly, suppression of antiapoptotic signaling specifically mediated by myeloid cell leukemia sequence 1 was sufficient to sensitize the uterine myocyte to undergo apoptotic cell death. These data demonstrate that elevated myeloid cell leukemia sequence 1 levels are sufficient to confer apoptotic resistance on the human uterine myocyte despite highly elevated levels of active CASP3.
authors.affiliation: Department of Obstetrics, Gynecology and Reproductive Sciences, Magee Women's Research Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Alyssa
authors.initials: A
authors.lastname: Stephenson-Famy
authors.forename: Jason
authors.initials: J
authors.lastname: Marks
authors.forename: Arvind
authors.initials: A
authors.lastname: Suresh
authors.forename: Stanley N
authors.initials: SN
authors.lastname: Caritis
authors.forename: Hygraiv
authors.initials: H
authors.lastname: Simhan
authors.forename: Pancharatnam
authors.initials: P
authors.lastname: Jeyasuria
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Condon
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism / Q000502:physiology*; D002374:Catalase / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D053938:DNA Fragmentation; D004789:Enzyme Activation; D053222:Fas Ligand Protein / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D032342:Muscle Cells / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011247:Pregnancy; D061251:Primary Cell Culture; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014466:Ultraviolet Rays; D014599:Uterus / Q000166:cytology*
chemical_list: D051017:Apoptosis Regulatory Proteins; D053222:Fas Ligand Protein; C579095:MCL1 protein, human; C579094:Mcl1 protein, mouse; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D002374:Catalase; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; D053148:Caspase 3