Open AccessSUMO-4: A novel functional candidate in the human placental protein SUMOylation machinery
Author(s) -
Dora Baczyk,
Melanie C. Audette,
Sascha Drewlo,
Khrystyna Levytska,
John Kingdom
Publication year - 2017
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0178056
Subject(s) - sumo protein , placenta , biology , placentation , western blot , messenger rna , trophoblast , fetal membrane , gene isoform , andrology , microbiology and biotechnology , fetus , gene , ubiquitin , biochemistry , genetics , pregnancy , medicine
Background Small ubiquitin-like modifiers (SUMOs) conjugate to proteins post-translationally, thereby affecting target localization, activity and stability. Functional SUMO family members identified in the human placenta include SUMO-1 to SUMO-3, which are elevated in pre-eclampsia. Whether the fourth isoform, SUMO-4, plays a role in placental development and function remains unknown. Objectives We tested the hypothesis that SUMO-4 is expressed in the human placenta and demonstrates altered SUMOylation in pre-eclamptic pregnancies. Methods SUMO-4 mRNA (qRT-PCR) and protein (Western blot and immunohistochemistry) were measured in Jar cells, BeWo cells, first trimester placental villous explants and placental tissues across normal gestation and in pre-eclampsia. SUMO-4 expression in response to oxidative stress (H 2 O 2 : 0, 0.1, 1 and 5mM), as well as, hypoxia-reperfusion (O 2 : 1%, 8% and 20%) was measured. Lastly, SUMO-4 binding (covalently vs. non-covalently) to target proteins was investigated. Results SUMO-4 mRNA and protein were unchanged across gestation. SUMO-4 was present in the villous trophoblast layer throughout gestation. SUMO-4 mRNA expression and protein levels were increased ~2.2-fold and ~1.8-fold in pre-eclamptic placentas compared to age-matched controls, respectively (p<0.01). SUMO-4 mRNA and protein expression increased in Jars, BeWos and first trimester placental explants with 5mM H 2 O 2 treatment, as well as with exposure to hypoxia-reperfusion. SUMO-1 to SUMO-3 did not show consistent trends across models. SUMO-4 hyper-SUMOylation was predominantly covalent in nature. Conclusions SUMO-4 is expressed in normal placental development. SUMO-4 expression was increased in pre-eclamptic placentas and in models of oxidative stress and hypoxic injury. These data suggests that SUMO-4 hyper-SUMOylation may be a potential post-translational mechanism in the stressed pre-eclamptic placenta.