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The regulatory mechanism of extracellular Hsp90{alpha} on matrix metalloproteinase-2 processing and tumor angiogenesis.

ABSTRACT: Heat shock protein 90α (Hsp90α) is a ubiquitously expressed molecular chaperone that is essential for eukaryotic homeostasis. Hsp90α can also be secreted extracellularly, where it has been shown to be involved in tumor metastasis. Extracellular Hsp90α interacts with and promotes the proteolytic activity of matrix metalloproteinase-2 (MMP-2). However, the regulatory mechanism of Hsp90α on MMP-2 activity is still unknown. Here we show that Hsp90α stabilizes MMP-2 and protects it from degradation in tumor cells. Further investigation reveals that this stabilization effect is isoform-specific, ATP-independent, and mediated by the interaction between the Hsp90α middle domain and the MMP-2 C-terminal hemopexin domain. Moreover, this mechanism also applies to endothelial cells that secrete more Hsp90α in their proliferating status. Furthermore, endothelial cell transmigration, Matrigel plug, and tumor angiogenesis assays demonstrate that extracellular Hsp90α promotes angiogenesis in an MMP-2-dependent manner. In sum, this study provides new insights into the molecular mechanism of how Hsp90α regulates its extracellular client proteins and also reveals for the first time the function of extracellular Hsp90α in promoting tumor angiogenesis.

SUBMITTER: Song X

PROVIDER: S-EPMC3000986 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Matrix metalloproteinase-2 (MMP-2) expression is often up-regulated in advanced cancers and known to play an important role in tumor angiogenesis. We previously showed that adenoviral-mediated delivery of siRNA for MMP-2 (Ad-MMP-2-Si) inhibited lung cancer growth, angiogenesis, and metastasis. In this study, we investigated the signaling mechanisms involved in Ad-MMP-2-Si-mediated inhibition of angiogenesis. Ad-MMP-2-Si treatment inhibited neovascularization in vivo as determined by mouse dorsal air sac model, and conditioned medium from Ad-MMP-2-Si-infected A549 lung cancer cells (Ad-MMP-2-Si-CM) inhibited endothelial tube formation in vitro. Ad-MMP-2-Si-CM decreased proliferation as determined by Ki-67 immunofluorescence and induced apoptosis in endothelial cells as determined by terminal deoxynucleotidyl-transferase-mediated dUTP nick-end labeling (TUNEL) assay. Furthermore, Ad-MMP-2-Si-CM inhibited AKT phosphorylation and induced phosphorylation of extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase in endothelial cells. Overexpression of constitutively active AKT reversed the Ad-MMP-2-Si-CM-mediated inhibition of tube formation and induction of ERK phosphorylation. Conversely, Ad-MMP-2-Si-CM induced tissue inhibitor of metalloproteinase (TIMP) 3 expression, and the interaction of vascular endothelial growth factor 2 and TIMP-3 was determined by coimmunoprecipitation experiments. TIMP-3 induction was mediated by ERK activation. In addition, electrophoretic mobility shift and chromatin immunoprecipitation assays show that Sp1 transcription factor mediated Ad-MMP-2-Si-CM-stimulated increase of TIMP-3. Vasculature destruction was confirmed with colocalization studies with TUNEL and an endothelial marker, CD31, in tumor sections of Ad-MMP-2-Si-treated mice. Our data collectively suggest that MMP-2 inhibition induces endothelial apoptosis in vivo and inhibits endothelial tube formation. These experiments provide the first evidence that inhibition of p-AKT and induction of p-ERK1/2 are crucial events in the induction of TIMP-3-mediated endothelial apoptosis in MMP-2 inhibited lung tumors.

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The regulatory mechanism of extracellular Hsp90{alpha} on matrix metalloproteinase-2 processing and tumor angiogenesis.

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