Contribution of endogenously expressed Trp1 to a Ca2+-selective, store-operated Ca2+ entry pathway

Heterologous expression of the transient receptor potential-1 gene product (Trp1) encodes for a Ca2+ entry pathway, though it is unclear whether endog enous Trp1 contributes to a selective store-operated Ca2+ entry current. We examined the role of Trp1 in regulating both store-operated Ca2+ entry and a store-operated Ca2+ entry current, I-SOC, in A549 and endothelial cells. Twenty different 'chimeric' 2'-O-(2-methoxy) ethylphosphothioate antisense oligonucleotides were transfected separately using cationic lipids and scr eened for their ability to inhibit Trp1 mRNA. Two hypersensitive regions we re identified, one at the 5' end of the coding region and the second in the 3' untranslated region beginning six nucleotides downstream of the stop co don. Antisense oligonucleotides stably decreased Trp1 at concentrations ran ging from 10 to 300 nM, for up to 72 h. Thapsigargin increased global cytos olic Ca2+ and activated a I-SOC, which was small (-35 pA @ -80 mV), reverse d near +40 mV, inhibited by 50 muM La3+, and exhibited anomalous mole fract ion dependence. Inhibition of Trp1 reduced the global cytosolic Ca2+ respon se to thapsigargin by 25% and similarly reduced I-SOC by 50%. These data co llectively support a role for endogenously expressed Trp1 in regulating a C a2+-selective current activated upon Ca2+ store depletion.