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

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

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Calcium Signaling / physiology*
  • Cells, Cultured
  • Female
  • Humans
  • Large-Conductance Calcium-Activated Potassium Channels / metabolism*
  • Low Density Lipoprotein Receptor-Related Protein-1 / metabolism
  • Myocytes, Smooth Muscle / metabolism*
  • Myometrium / cytology
  • Myometrium / metabolism*
  • Pregnancy / metabolism*
  • Pregnancy Trimester, Third / metabolism
  • alpha-Macroglobulins / metabolism*

Substances

  • LRP1 protein, human
  • Large-Conductance Calcium-Activated Potassium Channels
  • Low Density Lipoprotein Receptor-Related Protein-1
  • alpha-Macroglobulins