Effect of latrunculin B, jasplakinolide and brefeldin A on the store-dependent Ca2+ entry in macrophages

Using Fura-2AM microfluorimetry, effect of actin filament modifiers and vesicular trafficking inhibitor on the store-dependent Ca2+ entry induced by purinergic agonists (ATP, UTP) and endoplasmic Ca2+-ATPase inhibitors (thapsigargin, cyclopiazonic acid) in rat peritoneal macrophages was investigated. It was shown that inhibition of actin polymerization by latrunculin B had a biphasic time-dependent effect on Ca2+ entry, showing an initial potentiation followed by inhibition of Ca2+ entry. Moreover, addition of latrunculin B after induction of store-dependent Ca2+ entry inhibited the Ca2+ influx. Jasplakinolide, which reorganizes actin filaments into a tight cortical layer adjacent to the plasma membrane, prevented activation of store-dependent Ca2+ entry but did not modify this process after its activation. Vesicular transport inhibitor brefeldin A, which inactivates arfproteins, inhibited activation of store-dependent Ca2+ entry but did not alter this mechanism once being initiated. These data are compatible with the sectretion-like coupling model for store-dependent Ca2+ entry in macrophages based on a reversible trafficking and coupling of Ca2+ store with the plasma membrane.