Cancer is a life-threatening disorder and one of the major prevailing health problems. The Matrix Metalloproteinase-9, also called gelatinase B, is a critical component of the angiogenic switch driving metastasis in various cancers. Additionally it promotes osteoarthritis, atherosclerosis or heart failure. Under healthy conditions, the MMP-9 proteolytic activity is strictly regulated by the endogenous tissue inhibitors of matrix metalloproteinases (TIMPs), while disruption of this balance leads to a detrimental excess of active MMP-9. Specific inhibition of MMP-9 may prevent tumor growth therefore, it is essential to design potent inhibitors in order to compensate for the loss at physiological regulation. Even though many inhibitors have been studied, none was sufficiently specific and efficient for any individual MMP. In an attempt to clarify important determinants for the specific inhibition of MMP-9, the inactive E402Q mutant of the truncated catalytic domain of human MMP-9 was prepared, and the X-ray crystal structures of this recombinant miniMMP-9 were determined with a number of catalytic zinc-directed synthetic inhibitors of different binding type. The complex structures of MMP-9 with relatively selective, tight binding inhibitors, namely a pyrimidine-2,4,6-trione (RO206-0222), a phosphinic acid (AM409), a carboxylate (An1), a trifluoromethyl hydroxamic acid inhibitor (MS560), and a difluoro carboxylate inhibitor (MJ24) were solved. The crystal structures revealed that these five inhibitors bind in a similar manner, compromising between optimal coordination of the catalytic zinc, favourable hydrogen bond formation in the active-site cleft, and accommodation of their large P1’ groups in the overall rigid S1’ cavity. Furthermore, three MMP inhibitors were designed which are capable of differentiating the gelatinases MMP-2 and -9 from the other members of the MMPs family, by applying the concept of bivalent inhibitors: Al134 (Peg4), Al134 (Peg6), and Al134 (Peg8). The latter one proved that the bivalent inhibition concept for MMP-9 is working in principle, but requires additional fine tuning of the compound.
Dimerization is an important mechanism to regulate activity of MMPs, in particular for the cancer related MMP-2. MT1-MMP Hpex fixes, through a bound TIMP-2, a proMMP-2 molecule presenting a scissile peptide bond toward a second non-inhibited MT1-MMP molecule, which facilitates proMMP-2 activation. For a structural analysis of the MT1-MMP dimerization the recombinant MT1-MMP hemopexin domain was crystallized. The crystals contain a monomer with two different, symmetrical and asymmetrical binding sites. The symmetrical MT1-MMP-Hpex dimer interface is mixed polar and hydrophobic, and served as a model for MT1-MMP dimerization. In contrast to the corresponding asymmetrical MT1-MMP dimer, the symmetrical complex is in accordance with the known dimerization of the transmembrane segments including the cytoplasmic tail. Furthermore, the complex formation of Hpex MT1-MMP and one TIMP-2 molecule via its C-terminal part is also possible.
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Cancer is a life-threatening disorder and one of the major prevailing health problems. The Matrix Metalloproteinase-9, also called gelatinase B, is a critical component of the angiogenic switch driving metastasis in various cancers. Additionally it promotes osteoarthritis, atherosclerosis or heart failure. Under healthy conditions, the MMP-9 proteolytic activity is strictly regulated by the endogenous tissue inhibitors of matrix metalloproteinases (TIMPs), while disruption of this balance leads...
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