title: Estrogen modulation of MgATPase activity of nonmuscle myosin-II-B filaments.
abstract: The study tested the hypothesis that estrogen controls epithelial paracellular resistance through modulation of myosin. The objective was to understand how estrogen modulates nonmuscle myosin-II-B (NMM-II-B), the main component of the cortical actomyosin in human epithelial cervical cells. Experiments used human cervical epithelial cells CaSki as a model, and end points were NMM-II-B phosphorylation, filamentation, and MgATPase activity. The results were as follows: 1) treatment with estrogen increased phosphorylation and MgATPase activity and decreased NMM-II-B filamentation; 2) estrogen effects could be blocked by antisense nucleotides for the estrogen receptor-alpha and by ICI-182,780, tamoxifen, and the casein kinase-II (CK2) inhibitor, 5,6-dichloro-1-beta-(D)-ribofuranosylbenzimidazole and attenuated by AG1478 and PD98059 (inhibitors of epithelial growth factor receptor and ERK/MAPK) but not staurosporine [blocker of protein kinase C (PKC)]; 3) treatments with the PKC activator sn-1,2-dioctanoyl diglyceride induced biphasic effect on NMM-II-B MgATPase activity: an increase at 1 nm to 1 microM and a decrease in activity at more than 1 microM; 4) sn-1,2-dioctanoyl diglyceride also decreased NMM-II-B filamentation in a monophasic and saturable dose dependence (EC(50) 1-10 microM); 5) when coincubated directly with purified NMM-II-B filaments, both CK2 and PKC decreased filamentation and increased MgATPase activity; 6) assays done on disassembled NMM-II-B filaments showed MgATPase activity in filaments obtained from estrogen-treated cells but not estrogen-depleted cells; and 7) incubations in vitro with CK2, but not PKC, facilitated MgATPase activity, even in disassembled NMM-II-B filaments. The results suggest that estrogen, in an effect mediated by estrogen receptor-alpha and CK2 and involving the epithelial growth factor receptor and ERK/MAPK cascades, increases NMM-II-B MgATPase activity independent of NMM-II-B filamentation status.
authors.affiliation: Department of Reproductive Biology, Case Western Reserve University, Cleveland, Ohio 44106, USA. gig@cwru.edu
authors.forename: George I
authors.initials: GI
authors.lastname: Gorodeski
mesh_terms: D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D002460:Cell Line; D002584:Cervix Uteri / Q000166:cytology; D003599:Cytoskeleton / Q000187:drug effects / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D066246:ErbB Receptors / Q000378:metabolism; D047628:Estrogen Receptor alpha / Q000378:metabolism; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D024501:Nonmuscle Myosin Type IIB / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects
chemical_list: D047628:Estrogen Receptor alpha; D004967:Estrogens; D066246:ErbB Receptors; D017301:Ca(2+) Mg(2+)-ATPase; D024501:Nonmuscle Myosin Type IIB