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.
"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 full-length human β3 integrin subunit, LoVo cells transfected with human furin and CHO cells transfected with the full-length human αV integrin subunit and with the mutant αV integrin subunit with the inactivated furin cleavage site were prepared and characterized earlier , , , , . In the furin-resistant αV integrin mutant, Ala-889 and Ala-890 substituted for Lys-889 and Arg-890 of the furin cleavage motif. "
[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.
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.
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.
PLoS ONE 01/2013; 8(1):e54290. DOI:10.1371/journal.pone.0054290 · 3.23 Impact Factor
"Previous studies suggest that one integrin can regulate the activation state of other integrins in the same cell, a mechanism called transdominant inhibition (Gonzalez et al., 2009). For example, increased expression of αvβ3 suppresses α2βl-dependent adhesion of breast carcinoma cells (Baciu et al., 2003). We recently demonstrated that αvβ5/β6 integrins down-regulate the α2β1- dependent cell migration of colonic adenocarcinoma cells. "
[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.
Biology of the Cell 07/2011; 103(11):519-29. DOI:10.1042/BC20100147 · 3.51 Impact Factor
"Integrin avb3 is fundamental in crossing the blood–brain barrier and it is also able to regulate the binding of a2b1 to fibronectin and the conversion of pro-av to the mature av subunit. This conversion is achieved by MT1-MMP in breast carcinoma cells (Baciu et al., 2003), but is usually performed by proprotein convertases (PCs) (Bassi et al., 2005). Infection of murine macrophages with T. gondii did not interfere initially with expression of av or b3 at the cell surface. "
[Show abstract][Hide abstract] ABSTRACT: Toxoplasmosis is a world wide spread zoonosis caused by Toxoplasma gondii, an obligate intracellular parasite that is able to disseminate into deep tissues and cross biological barriers, reaching immunoprivileged sites such as the brain and retina. The parasite is able to infect macrophages and dendritic cells for dispersal throughout the body. However, the molecular principals or outcomes of the subversion of the host cell are largely unknown. We evaluated the involvement of host invasive machinery in the migration of T. gondii infected murine cells from a monocytic/macrophage lineage. Migration in Matrigel of infected macrophages was augmented after 48 h of infection, and inhibition of metalloproteinases abolished migration. We also demonstrated that T. gondii infection induces a decreasing of CD44 at cell surface independent of the ERK signaling pathway, and that secretion of active MMP9 is augmented upon infection. Infected macrophages showed increased expression of MT1-MMP and ADAM10 membrane matrix metalloproteinases. Furthermore, processing of pro-alpha v and pro-beta 3 in T. gondii infected cells seems to depend on metalloproteinases to generate functional mature integrin alpha v beta 3 molecules, with no evidence of the involvement of proprotein convertase pathway.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.