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Proc Natl Acad Sci U S A. 2016 Apr 19;113(16):E2335-44. doi: 10.1073/pnas.1516863113. Epub 2016 Apr 4.

BKCa channel regulates calcium oscillations induced by alpha-2-macroglobulin in human myometrial smooth muscle cells.

Author information

1
Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110;
2
Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242;
3
Department of Psychiatry and Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO 63110;
4
Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110.
5
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.

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.

KEYWORDS:

BKCa; LRP1; intracellular calcium; myometrial smooth muscle; α2M

PMID:
27044074
PMCID:
PMC4843459
DOI:
10.1073/pnas.1516863113
[Indexed for MEDLINE]
Free PMC Article

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