vk 05/06 Stefanidakis Michael: Biokemia: Cell-Surface Association between Progelatinases and ß2 Integrins: Role of the Complexes in Leukocyte Migration

vk 05/06 Stefanidakis Michael: Biokemia: Cell-Surface Association between Progelatinases and ß2 Integrins: Role of the Complexes in Leukocyte Migration

Lähettäjä: stefanid 23.12.2005 14:59

Michael Stefanidakis Biotieteellinen tiedekunta Biokemia 3.2.2006Cell-Surface Association between Progelatinases and ß2 Integrins: Role of the Complexes in Leukocyte MigrationLeukocyte motility is known to be dependent on both ß2-integrins and matrix metalloproteinases MMP-2/-9 or gelatinases, capable of mediating leukocyte adhesion and the proteolysis needed for invasion, respectively. We have used phage display technology to identify peptide sequences interacting with the aM integrin I domain, an about 200 amino acid residue sequence known to be responsible for ligand binding in ß2 integrins. One of the peptides contained a sequence very similar to the conserved DELW(S/T)LG sequence found in MMP-2 and –9. In several binding, migration and mutation analysis studies, we showed that the integrin recognition sequence mapped to the MMP catalytic domain, specifically bound to the aM I domain, and it inhibited migration of leukocytes in vitro. Subcellular fractionation experiments revealed that the proMMP-9/aMß2 complex was formed intracellularly and could be translocated to the cell surface upon cell activation. This interaction was efficiently blocked by a peptide sequence derived from the catalytic domain of MMP-9. Also, a novel small-molecule ligand to the aM I domain, identified by screening a combinatorial library, inhibited DDGW-phage binding to the I domain and reduced leukocyte infiltration to an inflammatory site in vivo. The concept that MMPs associate with integrins, as well as its importance in some physiological and pathological conditions has been advanced previously but has not been examined on leukocytes. Gelatinases not only play an important role in cell migration, tissue remodelling and angiogenesis during development, but are also involved in the progression and invasiveness of many cancers, including leukemias. We showed that MMP-9 association with ß2 integrins seems to play an important role in leukemia growth and dissemination in vivo, as inhibition of complex formation significantly improved the survival of mice that developed leukemia. These findings suggest that the integrin/MMP-9 complex may serve as a functional target for intervention in human acute leukemias.