“Differential Involvement of SAC influx in ATP Modulation of MAPKs in Osteoblasts and Breast Cells”

SCODELARO BILBAO, PAOLA GABRIELA; KATZ, SEBASTIÁN; SANTILLÁN, GRACIELA

Rosario, Santa Fe, Argentina

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2006

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Extracellular nucleotides increase intracellular calcium concentration ([Ca2+]i) in breast cancer MCF-7 and osteoblastic ROS 17/2.8 osteosarcoma cells. This effect is mainly due to Ca2+ release from inner stores. As previously seen in osteoblasts, using spectrofluorimetric [Ca2+]i measurements, stimulation of MCF-7 cells with ATP or UTP sensitized them to a mechanical stress activated calcium (SAC) influx. ATPg-S >ATP > UTP >> ADPß-S = ADP elevated [Ca2+]i, in MCF-7 cells, suggesting the presence of  P2Y2 receptor (P2Y2R) subtype and that SAC influx is dependent on P2Y2R activation. Gd3+ (10µM) inhibited the ATP-dependent SAC influx. U73122 and neomycin, PI-PLC inhibitors, and 2-APB, an IP3 receptor antagonist, abolished the ATP dependent- Ca2+ release and SAC influx. Western blot analysis revealed that P2Y2R stimulation induced ERK1/2, p38 and JNK1 MAPK phosphorylation in both cell lines. Cell treatment with neomycin, Gd3+ or a Ca2+ free medium (plus EGTA 0.5 mM) reduced this effect induced by ATP in ROS 17/2.8 cells, whereas in MCF-7 cells, U73122 and 2-APB completely inhibited the ATP-dependent MAPKs activation while EGTA or Gd3+ did not. The results show the presence of ATP-dependent SAC influx in both cell lines. Different from ROS17/2.8 cells, MAPK phosphorylation induced by ATP in breast tumor cells is dependent on PI-PLC/IP3/Ca2+ release but not on SAC influx.