Store-operated Ca²⁺entry in porcine airway smooth muscle

Abstract

Ca(2+) influx triggered by depletion of sarcoplasmic reticulum (SR) Ca(2+) stores [mediated via store-operated Ca(2+) channels (SOCC)] was characterized in enzymatically dissociated porcine airway smooth muscle (ASM) cells. When SR Ca(2+) was depleted by either 5 microM cyclopiazonic acid or 5 mM caffeine in the absence of extracellular Ca(2+), subsequent introduction of extracellular Ca(2+) further elevated [Ca(2+)](i). SOCC was insensitive to 1 microM nifedipine- or KCl-induced changes in membrane potential. However, preexposure of cells to 100 nM-1 mM La(3+) or Ni(2+) inhibited SOCC. Exposure to ACh increased Ca(2+) influx both in the presence and absence of a depleted SR. Inhibition of inositol 1,4,5-trisphosphate (IP)-induced SR Ca(2+) release by 20 microM xestospongin D inhibited SOCC, whereas ACh-induced IP(3) production by 5 microM U-73122 had no effect. Inhibition of Ca(2+) release through ryanodine receptors (RyR) by 100 microM ryanodine also prevented Ca(2+) influx via SOCC. Qualitatively similar characteristics of SOCC-mediated Ca(2+) influx were observed with cyclopiazonic acid- vs. caffeine-induced SR Ca(2+) depletion. These data demonstrate that a Ni(2+)/La(3+)-sensitive Ca(2+) influx via SOCC in porcine ASM cells involves SR Ca(2+) release through both IP(3) and RyR channels. Additional regulation of Ca(2+) influx by agonist may be related to a receptor-operated, noncapacitative mechanism.

Expression and coupling of neurokinin receptor subtypes to inositol phosphate and calcium signaling pathways in human airway smooth muscle cells

“…Cells were then exposed to 10 M cyclopiazonic acid [CPA; an inhibitor of SR Ca 2ϩ -ATPase (SERCA)] in 0-Ca 2ϩ modified HBSS with 1 mM EGTA, resulting in passive SR depletion with continued SR Ca 2ϩ leak (likely from both IP3-and ryanodinesensitive SR stores). As in previous studies (5,46), a gradual elevation of [Ca 2ϩ ]i was typically noted that eventually reached a plateau or started trending downward (because plasma membrane Ca 2ϩ efflux was not inhibited). Pretreatment with SKF-96365 (10 M; positive control inhibitor), 2-APB (10 M), ryanodine (100 M), or caffeine (10 mM) was performed, and then CaCl 2 (to achieve a final extracellular Ca 2ϩ concentration of 2.5 mM) was rapidly reintroduced (in the continued presence of verapamil, KCl, and CPA) and the peak fluorescence was measured.…”

“…These experiments were designed to examine the effects of 2-APB, caffeine, or ryanodine on store-operated Ca 2ϩ entry (SOCE) in HASM. SOCE was evaluated using previously described protocols (5,46,49). Extracellular Ca 2ϩ was removed by exposure to 0-Ca 2ϩ modified HBSS containing 1 mM EGTA for 10 min.…”

Regulation of store-operated Ca2+entry by CD38 in human airway smooth muscle

“…The techniques for [Ca 2ϩ ]i measurements in ASM using fluorescent indicators have been previously described (6,58). Briefly, cells plated in eight-well borosilicate coverglass chambers were incubated for 45 min in 5 M fura-2 AM (Molecular Probes), washed, and perfused with HBSS.…”

“…Ca 2ϩ influx in ASM can occur through voltage-gated (59), receptor-operated (33), and/or store-operated channels (6). In the last case, store-operated Ca 2ϩ entry (SOCE) is triggered by depletion of SR Ca 2ϩ stores (6,41,42,49,55,56).…”

“…In the last case, store-operated Ca 2ϩ entry (SOCE) is triggered by depletion of SR Ca 2ϩ stores (6,41,42,49,55,56). We and others have shown that different transient receptor potential channel (TRPC) isoforms are expressed in ASM (6,58). In a recent study using human ASM, we further demonstrated that TNF␣ treatment increases SOCE (58).…”