15 research outputs found
Ulipristal acetate interferes with actin remodeling induced by 17β-estradiol and progesterone in human endometrial stromal cells
Ulipristal acetate (UPA) is a selective progesterone receptor modulator (SPRM) used for emergency contraception and for the medical management of symptomatic uterine fibroids (UF). Treatment with UPA turns in amenorrhea and UF volume reduction. Treatment with UPA is associated with the frequent development of benign, transitory endometrial changes known as SPRM-associated endometrial changes (PAECs). Why PAECs develop and their biological or cellular basis is unknown. Sex steroids, including estrogen and progesterone, are established modulators of the actin cytoskeleton in various cells, including endometrial cells. This explains several morphological and functional changes in endometrial cells. We thus hypothesized that UPA may alter the appearance of the endometrium by interfering with the actions of 17β-estradiol (E2) or progesterone (P4) on actin dynamics. We isolated and cultured human endometrial stromal cells (ESC) from endometrial biopsies from healthy fertile women. Treatment with E2 or P4 stimulated visible actin rearrangements with actin remodeling toward the membrane. Activation through phosphorylation of the actin regulatory proteins, Moesin, and focal adhesion kinase (FAK), hacked actin remodeling induced by E2 and P4. Membrane re-localization of Paxillin and Vinculin were also induced by E2 and P4, showing the formation of focal adhesion complexes. All these E2 and P4 actions were inhibited by co-treatment with UPA, which was otherwise inactive if given alone. The cytoskeletal changes induced by E2 and P4 turned into increased motility of ESC, and UPA again blocked the actions E2 and P4. In conclusion, we find that UPA interferes with the cytoskeletal actions of E2 and P4 in ESC. This finding helps understanding the mode of actions of SPRMs in the endometrium and may be relevant for other potential clinical applications of UPA
Introduction to magnetic resonance methods in photosynthesis
Electron paramagnetic resonance (EPR) and, more recently, solid-state nuclear magnetic resonance (NMR) have been employed to study photosynthetic processes, primarily related to the light-induced charge separation. Information obtained on the electronic structure, the relative orientation of the cofactors, and the changes in structure during these reactions should help to understand the efficiency of light-induced charge separation. A short introduction to the observables derived from magnetic resonance experiments is given. The relation of these observables to the electronic structure is sketched using the nitroxide group of spin labels as a simple example
An EPR spin label study of the quinol oxidase, E. coli cytochrome bo3: A search for redox induced conformational changes:A search for redox induced conformational changes
A search for conformational changes at the cytosolic entrance to the proton channels of the heme-copper quinol oxidase (QO), cytochrome bo3, E. coli, has been carried out using site directed nitroxide spin labeling (SDSL) of cysteine residues. These were positioned at R134 and R309, on loops that link helices II and III and VI and VII at the entrances to the D and K proton channels, respectively. The motional characteristics of both labels have been determined using X- and W-band EPR spectroscopy at room temperature in selected redox levels in the reaction sequence of QO with oxygen, namely, the mixed valence carbon monoxide form (COMV), the oxidized (O) and super-oxidized (P M) states. The O to PM step is accompanied by the uptake of protons through the K pathway. We find no evidence for changes in the motional characteristics of either label that are expected to be associated with helical motions at the entrances to the channels. Because kinetic studies of mutants show that the redox gating of protons occurs deep within the D channel close to the heme-copper site, the present study implies that no motion is transmitted to the ends of the helices