“Modulation of JNK1 MAPK by ATP in osteoblasts and breast cancer cells: involvement of mechanical stress activated (SAC) calcium influx”

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

Rosario, Santa Fe

Congreso; XXIII Reunión Anual de la Asociación Argentina de Osteología y Metabolismo Mineral; 2006

Asociación Argentina de Osteología y Metabolismo Mineral

Extracellular nucleotides may function as important messengers in many cell types acting through P2 receptors. We have previously reported that stimulation of P2Y2 receptors by ATP sensitizes mechanical stress activated channels (SAC) leading to calcium influx both in osteoblast-like osteosarcoma (ROS-A 17/2.8) and human breast cancer (MCF-7) cell lines. This SAC influx participates in p38 and ERK 1/2 MAPKs activation only in the case of ROS-A 17/2.8 cells. In the present work we studied the involvement of SAC influx in the modulation of c-Jun NH2-terminal kinase (JNK) by ATP in these systems. Western blot analysis showed that JNK1 was rapidly (5 min) phosphorylated by 5 µM ATP in a dose- and time-dependent manner in ROS-A 17/2.8 and MCF-7 cells, whereas phosphorylation of the JNK2 isoform was only observed after 15 min of cell incubation with ATP in breast cells. In both cell systems, JNK1 activation was reduced by 1.0-2.5 mM neomycin or by 150 mM 2-APB, a blocker of IP3 receptors, suggesting the participation of PLC and intracellular calcium mobilization in such response, as in the case of ERK1/2 and p38. Cell incubation in a Ca2+ free medium (+ 0.5 mM EGTA) or the use of 5 mM Gd3+, a SAC channel inhibitor, only reduced JNK1 phosphorylation by ATP in the case of osteoblasts. These results suggest the involvement of intracellular calcium mobilization in the activation of JNK1 by ATP in osteoblasts and breast cancer cells. Although SAC influx was observed in both cell lines, it only participates in JNK1 activation by ATP in ROS-A 17/2.8 cells.