Molecular Scissors: From Biomaterials Implant to Tissue Remodeling - Biologically Responsive Biomaterials for Tissue Engineering - page 26

TIMP-2 [ 38, 79, 127 ] . Some authors [ 127 ] observed that TIMP-2 has a double effect
on MMP-2 since MT-MMP-mediated proMMP-2 activation requires a tiny amount
of TIMP-2 to make activation progress, whereas a higher concentration of TIMP-2
inhibits MMP-2 [ 64 ]. TIMP-3 may inhibit MMP-2 and MMP-9 [ 122 ] , and TIMP-4
is a good inhibitor for all MMPs [ 109 ]. Tissue levels for TIMPs in ECM are largely
exceeding MMP levels in the same areas. TIMPs act also as growth hormone and
inductor for apoptosis (mainly TIMP3). TIMPs transcription process is regulated by
cytokines and growth factors, involved in inflammation and remodeling processes.
Natural inhibitors for MMP may represent important performers in this play. Some
authors have described the close relation between MMP-2-TIMP-2 and MMP-9-
TIMP-1 enzyme-inhibitor pairs [ 86 ]. Interactions between these pairs are indeed
very complex and widely investigated from various points of view, by different
experimental means [ 102 ] and for different purposes. TIMP-2 is involved in MMP-2
activation at the cell surface by forming a complex with MT1-MMP. Thus, TIMP-2
can play a dual role during interaction with MMP-2. The biochemical relationship
between TIMP-2 and MMP-2 may induce surface-mediated enzyme activation,
while simple interaction TIMP-2-MMP-2 can determine enzyme inhibition. Our
group has also investigated the colocalization and complex relationship between
MMP-2, MMP-9 and TIMP-2, by molecular docking studies [ 92 ] to evaluate the
docking options for these enzymes and inhibitor. While we have found described in
the literature only the interaction MMP-9-TIMP-1, we have investigated the possi-
ble interaction between MMP-9 and TIMP-2 by molecular docking means. Thus we
have evaluated first the optimal positions of the TIMP-2 around MMP-2 molecule
and then, using a similitude procedure, we did the same thing for MMP-9-TIMP-2
complexes, for which there were no data regarding direct interaction. The investi-
gated docking molecular models were MMP2-TIMP2 and MMP-9-TIMP-2. For
the MMP-2-TIMP-2 enzyme-natural inhibitor complex, we have selected the 1gxd
file from Protein Data Bank (PDB) [ 9 ] from which there were picked individually
the molecules involved in this interaction, MMP-2 and TIMP-2. This selection was
followed by an identification of the specific regions involved in the enzyme-inhibi-
tor interactions, mainly the catalytic site and the hemopexinic site for MMP-2. This
enzyme has the unique property of being able to bind successively two TIMP-2
molecules, either on hemopexinic site (playing a role in enzyme activation) or on
the catalytic site (playing a role in enzyme inhibition). The docking process starts
from two known extracted structures that form a complex (MMP2-TIMP2 in 1gxd
file); the extraction of these proteins from the complex should not alter the initial
structure of the complex; this procedure was then validated by superposition. We
have checked this algorithm for this modeling software, while there is no available
data regarding the interaction MMP-9-TIMP-2. Following rigid docking and
filtering, we have a picture of the most probable positions for the inhibitor around
the enzyme. The filtering procedure was performed for localizing the catalytic and
the hemopexinic sites for TIMP-2 binding. The two resulted structures for MMP-2
and TIMP-2 (that occupies the best position near the catalytic site) were superposed
over the crystallographic model represented in the 1gxd file from PDB database.
Following superposition we have calculated also the Root Mean Square deviation