Alpha 2 M-LRP-1 induces ERK ½ phosphorylation by intracellular calcium and PKC activation in J774 cells.

CACERES LC; SAHORES MM; BARCELONA PF; SANCHEZ MC; CHIABRANDO GA

Santiago de Chile

Simposio; Chilean International Symposium on Lipoprotein Receptors: from cell biology to disease; 2006

LRP-1 is a LDL receptor gene family member synthesized and processed into 515-kDa extracelullar á chain and 85-kDa transmembrane and intracelullar â chain . LRP-1 á chain contains multiple ligand recognition sites and â chain harbors motifs for endocytosis and signaling. In addition to a2-macroglobulin-protease complexes (a2M*), LRP-1 also recognizes proteases and lactoferrin. The receptor-associated protein (RAP) inhibits the binding of LRP-1 ligands. Previously, we have demonstrated that á2M* promotes cell proliferation and intracelullar calcium in J774 cells by LRP-1, but the signaling mechanisms are unknown yet. Herein we evaluate the signaling effects of á2M* and other LRP-1 ligands. By Western blot we observed that a2M* 60 nM promoted MAPK-ERK1/2 phosphorilation, whereas RAP and lactoferrin did not induce it. The á2M*-induced ERK1-2-MAPK phosphorilation was inhibited by MEK-1 PD98059 inhibitor and RAP. When the J774 cells were cultured with Ca2+ antagonist BAPTA and the PKC Calphostin C inhibitor, the á2M*-induced ERK1-2-MAPK phosphorilation was blocked. In conclusion, á2M* induces ERK1-2-MAPK activation by intracellular calcium rises and PKC activation mediated by LRP-1 in J774 cells. Other LRP-1 ligands did not induce intracellular signal. Thus, the ligand recognition in the LRP-1 á chain might regulate and activate different downstream signaling pathways