title: High threshold of β1 integrin inhibition required to block collagen I-induced membrane type-1 matrix metalloproteinase (MT1-MMP) activation of matrix metalloproteinase 2 (MMP-2).
abstract: BACKGROUND
  Matrix metalloproteinase-2 (MMP-2) is an endopeptidase that facilitates extracellular matrix remodeling and molecular regulation, and is implicated in tumor metastasis. Type I collagen (Col I) regulates the activation of MMP-2 through both transcriptional and post-transcriptional means; however gaps remain in our understanding of the involvement of collagen-binding β1 integrins in collagen-stimulated MMP-2 activation.
  
  
  METHODS
  Three β1 integrin siRNAs were used to elucidate the involvement of β1 integrins in the Col I-induced MMP-2 activation mechanism. β1 integrin knockdown was analyzed by quantitative RT-PCR, Western Blot and FACS analysis. Adhesion assay and collagen gel contraction were used to test the biological effects of β1 integrin abrogation. MMP-2 activation levels were monitored by gelatin zymography.
  
  
  RESULTS
  All three β1 integrin siRNAs were efficient at β1 integrin knockdown and FACS analysis revealed commensurate reductions of integrins α2 and α3, which are heterodimeric partners of β1, but not αV, which is not. All three β1 integrin siRNAs inhibited adhesion and collagen gel contraction, however only the siRNA showing the greatest magnitude of β1 knockdown inhibited Col I-induced MMP-2 activation and reduced the accompanying upregulation of MT1-MMP, suggesting a dose response threshold effect. Re-transfection with codon-swapped β1 integrin overcame the reduction in MMP-2 activation induced by Col-1, confirming the β1 integrin target specificity. MMP-2 activation induced by TPA or Concanavalin A (Con A) was not inhibited by β1 integrin siRNA knockdown.
  
  
  CONCLUSIONS
  Together, the data reveals that strong abrogation of β1 integrin is required to block MMP-2 activation induced by Col I, which may have implications for the therapeutic targeting of β1 integrin.
authors.affiliation: Department of Nursing, Phetchabun Hospital, Phetchabun, Thailand ; Invasion and Metastasis Unit, St. Vincent's Institute, Fitzroy, Victoria 3065 Australia.
authors.forename: Kulrut
authors.initials: K
authors.lastname: Borrirukwanit
authors.affiliation: Department of Anatomy, Faculty of Dentistry, Chulalongkorn University, Chulalongkorn, Thailand.
authors.forename: Prasit
authors.initials: P
authors.lastname: Pavasant
authors.affiliation: Invasion and Metastasis Unit, St. Vincent's Institute, Fitzroy, Victoria 3065 Australia ; Institute of Health and Biomedical Innovation and School of Biomedical Sciences, Queensland University of Technology, Kelvin Grove, Queensland Australia.
authors.forename: Tony
authors.initials: T
authors.lastname: Blick
authors.affiliation: Invasion and Metastasis Unit, St. Vincent's Institute, Fitzroy, Victoria 3065 Australia.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Lafleur
authors.affiliation: Invasion and Metastasis Unit, St. Vincent's Institute, Fitzroy, Victoria 3065 Australia ; Department of Surgery, St Vincent's Hospital, University of Melbourne, Fitzroy, Victoria Australia ; Institute of Health and Biomedical Innovation and School of Biomedical Sciences, Queensland University of Technology, Kelvin Grove, Queensland Australia.
authors.forename: Erik W
authors.initials: EW
authors.lastname: Thompson
keywords: Invasion and metastasis; MMP-2 activation; Matrix metalloproteinase; Type I collagen; β1 Integrin