title: BKCa channel regulates calcium oscillations induced by alpha-2-macroglobulin in human myometrial smooth muscle cells.
abstract: The large-conductance, voltage-gated, calcium (Ca(2+))-activated potassium channel (BKCa) plays an important role in regulating Ca(2+)signaling and is implicated in the maintenance of uterine quiescence during pregnancy. We used immunopurification and mass spectrometry to identify proteins that interact with BKCain myometrium samples from term pregnant (≥37 wk gestation) women. From this screen, we identified alpha-2-macroglobulin (α2M). We then used immunoprecipitation followed by immunoblot and the proximity ligation assay to confirm the interaction between BKCaand both α2M and its receptor, low-density lipoprotein receptor-related protein 1 (LRP1), in cultured primary human myometrial smooth muscle cells (hMSMCs). Single-channel electrophysiological recordings in the cell-attached configuration demonstrated that activated α2M (α2M*) increased the open probability of BKCain an oscillatory pattern in hMSMCs. Furthermore, α2M* caused intracellular levels of Ca(2+)to oscillate in oxytocin-primed hMSMCs. The initiation of oscillations required an interaction between α2M* and LRP1. By using Ca(2+)-free medium and inhibitors of various Ca(2+)signaling pathways, we demonstrated that the oscillations required entry of extracellular Ca(2+)through store-operated Ca(2+)channels. Finally, we found that the specific BKCablocker paxilline inhibited the oscillations, whereas the channel opener NS11021 increased the rate of these oscillations. These data demonstrate that α2M* and LRP1 modulate the BKCachannel in human myometrium and that BKCaand its immunomodulatory interacting partners regulate Ca(2+)dynamics in hMSMCs during pregnancy.
authors.affiliation: Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110;
authors.forename: Monali
authors.initials: M
authors.lastname: Wakle-Prabagaran
authors.affiliation: Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110;
authors.forename: Ramón A
authors.initials: RA
authors.lastname: Lorca
authors.affiliation: Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110;
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Ma
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242;
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Stamnes
authors.affiliation: Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110;
authors.forename: Chinwendu
authors.initials: C
authors.lastname: Amazu
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242;
authors.forename: Jordy J
authors.initials: JJ
authors.lastname: Hsiao
authors.affiliation: Department of Psychiatry and Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO 63110;
authors.forename: Celeste M
authors.identifier: http://orcid.org/0000-0002-6854-5547
authors.initials: CM
authors.lastname: Karch
authors.affiliation: Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110.
authors.forename: Krzysztof L
authors.initials: KL
authors.lastname: Hyrc
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242;
authors.forename: Michael E
authors.initials: ME
authors.lastname: Wright
authors.affiliation: Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110; Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110 englands@wustl.edu.
authors.forename: Sarah K
authors.initials: SK
authors.lastname: England
mesh_terms: D000328:Adult; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D009215:Myometrium / Q000166:cytology / Q000378:metabolism*; D011247:Pregnancy / Q000378:metabolism*; D011263:Pregnancy Trimester, Third / Q000378:metabolism; D000511:alpha-Macroglobulins / Q000378:metabolism*
chemical_list: C475476:LRP1 protein, human; D051036:Large-Conductance Calcium-Activated Potassium Channels; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D000511:alpha-Macroglobulins
keywords: BKCa; LRP1; intracellular calcium; myometrial smooth muscle; α2M