Plasminogen-mediated matrix invasion and degradation by macrophages is dependent on surface expression of annexin II

Genetic evidence demonstrates the importance of plasminogen activation in t he migration of macrophages to sites of injury and inflammation, their remo val of necrotic debris, and their clearance of fibrin, These studies identi fied the plasminogen binding protein annexin II on the surface of macrophag es and determined its role in their ability to degrade and migrate through extracellular matrices, Calcium-dependent binding of annexin II to RAW264.7 macrophages was shown using flow cytometry and Western blot analysis of EG TA eluates, Ligand blots demonstrated that annexin II comigrates with one o f several proteins in lysates and membranes derived from RAW264.7 macrophag es that bind plasminogen. Preincubation of RAW264.7 macrophages with monocl onal anti-annexin II IgG inhibited (35%) their binding of I-125-Lys-plasmin ogen, Likewise, plasmin binding to human monocyte-derived macrophages and T HP-I monocytes was inhibited (50% and 35%, respectively) when cells were pr eincubated with anti-annexin II IgG. Inhibition of plasminogen binding to a nnexin II on RAW264.7 macrophages significantly impaired their ability to a ctivate plasminogen and degrade [H-3]. glucosamine-labeled extracellular ma trices, The migration of THP-1 monocytes through a porous membrane, in resp onse to monocyte chemotactic protein-1, was blocked when the membranes were coated with extracellular matrix. The addition of plasminogen to the monoc ytes restored their ability to migrate through the matrix-coated membrane, Preincubation of THP-1 monocytes with anti-annexin II IgG inhibited (60%) t heir plasminogen-dependent chemotaxis through the extracellular matrix, The se studies identify annexin II as a plasminogen binding site on macrophages and indicate an important role for annexin II in their invasive and degrad ative phenotype. (C) 2001 by The American Society of Hematology.