Lysophosphatidic acid induced nuclear translocation of nuclear factor-kB in Panc-1 cells by mobilizing cytosolic free calcium

Abstract

To clarify whether Lysophosphatidic acid (LPA) activates the nuclear translocation of nuclear factor-kappaB (NF-kappaB) in pancreatic cancer. Panc-1, a human pancreatic cancer cell line, was used throughout the study. The expression of LPA receptors was confirmed by reverse-transcript polymerase chain reaction (RT-PCR). Cytosolic free calcium was measured by fluorescent calcium indicator fura-2, and the localization of NF-kappaB was visualized by immunofluorescent method with or without various agents, which effect cell signaling. Panc-1 expressed LPA receptors, LP(A1), LP(A2) and LP(A3). LPA caused the elevation of cytosolic free calcium dose-dependently. LPA also caused the nuclear translocation of NF-kappaB. Cytosolic free calcium was attenuated by pertussis toxin (PTX) and U73122, an inhibitor of phospholipase C. The translocation of NF-kappaB was similarly attenuated by PTX and U73122, but phorbol ester, an activator of protein kinase C, alone did not translocate NF-kappaB. Furthermore, the translocation of NF-kappaB was completely blocked by Ca(2+) chelator BAPTA-AM. Thapsigargin, an endoplasmic-reticulum Ca(2+)-ATPase pump inhibitor, also promoted the translocation of NF-kappaB. Staurosporine, a protein kinase C inhibitor, attenuated translocation of NF-kappaB induced by LPA. These findings suggest that protein kinase C is activated endogenously in Panc-1, and protein kinase C is essential for activating NF-kappaB with cytosolic calcium and that LPA induces the nuclear translocation of NF-kappaB in Panc-1 by mobilizing cytosolic free calcium.