STORE-OPERATED CALCIUM-ENTRY PROMOTES SHAPE CHANGE IN PULMONARY ENDOTHELIAL-CELLS EXPRESSING TRP1

Activation of Ca2+ entry is known to produce endothelial cell shape ch ange, leading to increased permeability, leukocyte migration, and init iation of angiogenesis in conduit-vessel endothelial cells. The mode o f Ca2+ entry regulating cell shape is unknown. We hypothesized that ac tivation of store-operated Ca2+ channels (SOCs) is sufficient to promo te cell shape change necessary for these processes. SOC activation in rat pulmonary arterial endothelial cells increased free cytosolic Ca2 that was dependent on a membrane current having a net inward componen t of 5.45 +/- 0.90 pA/pF at -80 mV. Changes in endothelial cell shape accompanied SOC activation and were dependent on Ca2+ entry-induced re configuration of peripheral (cortical) filamentous actin (F-actin). Be cause the identity of pulmonary endothelial SOCs is unknown, but mamma lian homologues of the Drosophila melanogaster transient receptor pote ntial (trp) gene have been proposed to form Ca2+ entry channels in non excitable cells, we performed RT-PCR using Trp oligonucleotide primers in both rat and human pulmonary arterial endothelial cells. Both cell types were found to express Trp1, but neither expressed Trp3 nor Trp6 . Our study indicates that 1) Ca2+ entry in pulmonary endothelial cell s through SOCs produces cell shape change that is dependent on site-sp ecific rearrangement of the microfilamentous cytoskeleton and 2) Trp1 may be a component of pulmonary endothelial SOCs.