Membrane type-1 matrix metalloproteinase (MT1-MMP) processing of pro-alphav integrin regulates cross-talk between alphavbeta3 and alpha2beta1 integrins in breast carcinoma cells
We have recently demonstrated that in breast carcinoma MCF7 cells MT1-MMP processes the alphav, alpha3, and alpha5 integrin precursors generating the respective mature S-S-linked heavy and light alpha-chains. The precursor of alpha2 integrin subunit was found resistant to MT1-MMP proteolysis. The processing of the alphav subunit by MT1-MMP facilitated alphavbeta3-dependent adhesion, activation of FAK signaling pathway, and migration of MCF7 cells on vitronectin. To elucidate further the effects of MT1-MMP on cellular integrins, we examined the functional activity of alpha5beta1 and alpha2beta1 integrins in MCF7 cells expressing MT1-MMP. Either expression of MT1-MMP alone or its coexpression with alphavbeta3 failed to affect the functionality of alpha5beta1 integrin, and adhesion of cells to fibronectin. MT1-MMP, however, profoundly affected the cross-talk involving alphavbeta3 and alpha2beta1 integrins. In MT1-MMP-deficient cells, integrin alphavbeta3 suppressed the functional activity of the collagen-binding alpha2beta1 integrin receptor and diminished cell adhesion to type I collagen. Coexpression of MT1-MMP with integrin alphavbeta3 restored the functionality of alpha2beta1 integrin and, consequently, the ability of MCF7 cells to adhere efficiently to collagen. We conclude that the MT1-MMP-controlled cross-talk between alphavbeta3 and alpha2beta1 integrins supports binding of aggressive, MT1-MMP-, and alphavbeta3 integrin-expressing malignant cells on type I collagen, the most common substratum of the extracellular matrix.
[Show abstract] [Hide abstract] ABSTRACT: Background There is a growing appreciation of the role of proteolytic processes in human health and disease, but tools for analysis of such processes on a proteome-wide scale are limited. Furin is a ubiquitous proprotein convertase that cleaves after basic residues and transforms secretory proproteins into biologically active proteins. Despite this important role, many furin substrates remain unknown in the human proteome. Methodology/Principal Findings We devised an approach for proteinase target identification that combines an in silico discovery pipeline with highly multiplexed proteinase activity assays. We performed in silico analysis of the human proteome and identified over 1,050 secretory proteins as potential furin substrates. We then used a multiplexed protease assay to validate these tentative targets. The assay was carried out on over 3,260 overlapping peptides designed to represent P7-P1’ and P4-P4’ positions of furin cleavage sites in the candidate proteins. The obtained results greatly increased our knowledge of the unique cleavage preferences of furin, revealed the importance of both short-range (P4-P1) and long-range (P7-P6) interactions in defining furin cleavage specificity, demonstrated that the R-X-R/K/X-R↓ motif alone is insufficient for predicting furin proteolysis of the substrate, and identified ∼490 potential protein substrates of furin in the human proteome. Conclusions/Significance The assignment of these substrates to cellular pathways suggests an important role of furin in development, including axonal guidance, cardiogenesis, and maintenance of stem cell pluripotency. The novel approach proposed in this study can be readily applied to other proteinases.0Comments 10Citations
- "Original human glioma U251, breast carcinoma MCF-7 and colon carcinoma LoVo and Chinese hamster ovary CHO cells were obtained from ATCC. MCF-7 cells transfected with the fulllength human b3 integrin subunit, LoVo cells transfected with human furin and CHO cells transfected with the full-length human aV integrin subunit and with the mutant aV integrin subunit with the inactivated furin cleavage site were prepared and characterized earlier [29,46,51,52,53]. In the furin-resistant aV integrin mutant, Ala-889 and Ala-890 substituted for Lys-889 and Arg-890 of the furin cleavage motif. "
[Show abstract] [Hide abstract] ABSTRACT: Previous studies have reported that cross-talk between integrins may be an important regulator of integrin-ligand binding and subsequent signalling events that control a variety of cell functions in many tissues. We previously demonstrated that αvβ5/β6 integrin represses α2β1-dependent cell migration. The αv subunits undergo an endoproteolytic cleavage by protein convertases, whose role in tumoral invasion has remained controversial. Inhibition of convertases by the convertase inhibitor α1-PDX (α1-antitrypsin Portland variant), leading to the cell-surface expression of an uncleaved form of the αv integrin, stimulated cell migration toward type I collagen. Under convertase inhibition, α2β1 engagement led to enhanced phosphorylation of both FAK (focal adhesion kinase) and MAPK (mitogen-activated protein kinase). This outside-in signalling stimulation was associated with increased levels of activated β1 integrin located in larger than usual focal-adhesion structures and a cell migration that was independent of the PI3K (phosphoinositide 3-kinase)/Akt (also called protein kinase B) pathway. The increase in cell migration observed upon convertases inhibition appears to be due to the up-regulation of β1 integrins and to their location in larger focal-adhesion structures. The endoproteolytic cleavage of αv subunits is necessary for αvβ5/β6 integrin to control α2β1 function and could thus play an essential role in colon cancer cell migration.0Comments 6Citations
- "Furthermore, integrin cleavage by MT1-MMP enhanced cell adhesion on type I collagen and suppressed integrin cross-talk. In the presence of furin inhibitor, the repression of α2β1 adhesive functions was also totally suppressed (Baciu et al., 2003 ). In the present study, we verified in our cells that MT1-MMP is not expressed and PDX0 and PDX39P cells display plasma membrane integrins, mainly in an uncleaved form (Berthet et al., 2000 and results not shown). "
[Show abstract] [Hide abstract] ABSTRACT: Cells adhere to one another and/or to matrices that surround them. Regulation of cell-cell (intercellular) and cell-matrix adhesion is tightly controlled in normal cells, however, defects in cell adhesion are common in the majority of human cancers. Multilateral communication among tumor cells with the extracellular matrix (ECM) and neighbor cells is accomplished through adhesion molecules, ECM components, proteolytic enzymes and their endogenous inhibitors. There is sufficient evidence to suggest that reduced adherence is a tumor cell property engaged during tumor progression. Tumor cells acquire the ability to change shape, detach and easily move through spaces disorganizing the normal tissue architecture. This property is due to changes in expression levels of adhesion molecules and/or due to elevated levels of secreted proteolytic enzymes, including matrix metalloproteinases (MMPs). Among other roles, MMPs degrade the ECM and, therefore, prepare the path for tumor cells to migrate, invade and spread to distant secondary areas, where they form metastasis. Tissue inhibitors of metalloproteinases or TIMPs control MMP activities and, therefore, minimize matrix degradation. Both MMPs and TIMPs are involved in tissue remodeling and decisively regulate tumor cell progression including tumor angiogenesis. In this review, we describe and discuss data that support the important role of MMPs and TIMPs in cancer cell adhesion and tumor progression.0Comments 269Citations
- "Active forms of MMP-2 or MT1-MMP also interact with α v β 5 integrin and affect their membrane localization in a number of tumor cell lines including melanoma[70,71]. MT1-MMPs processesprecursors of α v α 5 and α 3 but not α 2 , integrins leading to α v β 3 mediated signaling and migration of breast cancer cells[72,73]. Cadherins are also targeted by MMPs. MMP-3 and MMP-7 have been shown to cleave membrane bound E-cadherin in MCF-7 breast cancer cells. "