ALPHA2-MACROGLOBULIN MEDIATES INTRACELLULAR CALCIUM LEVELS VIA LOW DENSITY LIPOPROTEIN RECEPTOR-RELATED PROTEIN (LRP) IN MACROPHAGE CELL LINE

BONACCI, GUSTAVO; CÁCERES, LEANDRO; CESCHIN, DANILO;CHIABRANDO, GUSTAVO.

San Carlos de Bariloche

Congreso; BARILOCHE PROTEIN SYMPOSIUM; 2003

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB) y la Sociedad Argentina de Biofísica (SAB)

Alpha-2-Macroglobulin is the most important human proteinase inhibitor, upon binding to proteinases it undergoes a conformational change, activated alpha2M (alpha2M*), that exposes receptor recognition sites allowed its interaction with LRP receptor. LRP is a scavenger receptor which belongs to LDL receptor gene family that binds to a variety of ligands, some of which trigger signal transduction. The biological function of alpha2M*/LRP interaction is not fully understood. Previously we have demonstrated that alpha2M* has proliferative effects on macrophage cell line, J774, which could be blocked with RAP (receptor associated protein), a specific antagonist to LRP. In this work we investigate the alpha2M* effect down stream to LRP interaction measuring intracellular calcium and MAPK phosphorylation on J774 cell line in the presence or absence of LPS. It is know that LPS down regulates the gene expression of LRP generating J774 cells fully depleted of LRP [J774(LRP-) cells]. By using Fura-2/AM and spectrofluorometric techniques we demonstrate that alpha2M* increase intracellular calcium in J774(LRP+) but not in J774(LRP-) cells. Lactoferrin, another ligand of LRP could also increase intracellular calcium in J774 (LRP+) cells. In addition, by immunoblotting we observed an increase in MAPK phosphorylation in J774 (LRP+) cells treated with alpha2M*. Thus, we propose that alpha2M*/LRP interaction is involved in intracellular signaling events, suggesting that calcium could be a key regulator of cell proliferation.