β2-integrin-mediated adhesion and intracellular Ca 2+ release in human eosinophils

Jennifer L. Bankers-Fulbright, Kathleen R. Bartemes, Gail M. Kephart, Hirohito Kita, Scott M. O'Grady

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Human eosinophils spontaneously adhere to various substrates in the absence of exogenously added activators. In the present study a method was developed for characterizing eosinophil adhesion by measuring changes in impedance. Impedance measurements were performed in HCO3-buffered HybriCare medium maintained in a humidified 5% CO2 incubator at 37°C. Impedance increased by more than 1 kΩ within minutes after eosinophils made contact with the substrate, reaching a peak within 20 min. Blocking mobilization of intracellular [Ca2+] that precedes adhesion with BAPTA-AM (10 μM) completely inhibited the rise in impedance as well as the changes in cell shape typically observed in adherent cells. However, lowering the extracellular [Ca2+] with 2.5 mM EGTA did not inhibit the increase in impedance. Pretreatment with anti-CD18 antibody to block substrate interactions with β2-integrins, or jasplakinolide (2 μM) to block actin reorganization, abolished the increase in impedance and adherent morphology of the cells. Exposure of eosinophils to the phosphatidylinositol 3 kinase inhibitor LY294002 (5 μM) or treatment with protein kinase C zeta pseudosubstrate to competitively inhibit activity of the enzyme significantly reduced the increase in impedance and inhibited the cell spreading associated with adhesion. These results demonstrate a novel method for measuring eosinophil adhesion and showed that, following formation of a tethered attachment, a rapid increase in intracellular [Ca2+] precedes the cytoskeletal rearrangements required for cell shape changes and plasma membrane-substrate interactions associated with adhesion.

Original languageEnglish (US)
Pages (from-to)99-109
Number of pages11
JournalJournal of Membrane Biology
Volume228
Issue number2
DOIs
StatePublished - Mar 2009

Keywords

  • Actin
  • Degranulation
  • Major basic protein
  • PI-3 kinase
  • β-Integrin

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology

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