10 research outputs found
Glycosylation Modulates Melanoma Cell α2β1 and α3β1 Integrin Interactions with Type IV Collagen
Although type IV collagen is heavily glycosylated, the influence of this posttranslational modification on integrin binding has not been investigated. In the present study, galactosylated and non-galactosylated triple-helical peptides have been constructed containing the α1(IV)382-393 and α1(IV)531-543 sequences, which are binding sites for the α2β1 and α3β1 integrins, respectively. All peptides had triple-helical stabilities of 37 °C or greater. The galactosylation of Hyl393 in α1(IV)382-393 and Hyl540 and Hyl543 in α1(IV)531-543 had a dose dependent influence on melanoma cell adhesion which was much more pronounced in the case of α3β1 integrin binding. Molecular modeling indicated that galactosylation occurred on the periphery of α2β1 integrin interaction with α1(IV)382-393 but right in the middle of α3β1 integrin interaction with α1(IV)531-543. The possibility of extracellular deglycosylation of type IV collagen was investigated, but no β-galactosidase-like activity capable of collagen modification was found. Thus, glycosylation of collagen can modulate integrin binding, and levels of glycosylation could be altered by reduction in expression of glycosylation enzymes but most likely not by extracellular deglycosylation activity
Monitoring and Inhibiting MT1-MMP during Cancer Initiation and Progression
Membrane-type 1 matrix metalloproteinase (MT1-MMP) is a zinc-dependent type-I transmembrane metalloproteinase involved in pericellular proteolysis, migration and invasion. Numerous substrates and binding partners have been identified for MT1-MMP, and its role in collagenolysis appears crucial for tumor invasion. However, development of MT1-MMP inhibitors must consider the substantial functions of MT1-MMP in normal physiology and disease prevention. The present review examines the plethora of MT1-MMP activities, how these activities relate to cancer initiation and progression, and how they can be monitored in real time. Examination of MT1-MMP activities and cell surface behaviors can set the stage for the development of unique, selective MT1-MMP inhibitors
Collagenolytic Matrix Metalloproteinase Activities toward Peptomeric Triple-Helical Substrates
Although
collagenolytic matrix metalloproteinases (MMPs) possess
common domain organizations, there are subtle differences in their
processing of collagenous triple-helical substrates. In this study,
we have incorporated peptoid residues into collagen model triple-helical
peptides and examined MMP activities toward these peptomeric chimeras.
Several different peptoid residues were incorporated into triple-helical
substrates at subsites P3, P1, P1′, and P10′ individually
or in combination, and the effects of the peptoid residues were evaluated
on the activities of full-length MMP-1, MMP-8, MMP-13, and MMP-14/MT1-MMP.
Most peptomers showed little discrimination between MMPs. However,
a peptomer containing <i>N</i>-methyl Gly (sarcosine) in
the P1′ subsite and <i>N</i>-isobutyl Gly (<i>N</i>Leu) in the P10′ subsite was hydrolyzed efficiently
only by MMP-13 [nomenclature relative to the α1Â(I)Â772–786
sequence]. Cleavage site analysis showed hydrolysis at the Gly–Gln
bond, indicating a shifted binding of the triple helix compared to
the parent sequence. Favorable hydrolysis by MMP-13 was not due to
sequence specificity or instability of the substrate triple helix
but rather was based on the specific interactions of the P7′
peptoid residue with the MMP-13 hemopexin-like domain. A fluorescence
resonance energy transfer triple-helical peptomer was constructed
and found to be readily processed by MMP-13, not cleaved by MMP-1
and MMP-8, and weakly hydrolyzed by MT1-MMP. The influence of the
triple-helical structure containing peptoid residues on the interaction
between MMP subsites and individual substrate residues may provide
additional information about the mechanism of collagenolysis, the
understanding of collagen specificity, and the design of selective
MMP probes