Low-Density Lipoprotein Receptor-Related Protein-1 Mediates Endocytic Clearance of Tissue Inhibitor of Metalloproteinases-1 and Promotes Its Cytokine-Like Activities
Abstract:Tissue inhibitor of metalloproteinases-1 (TIMP-1) regulates the extracellular matrix turnover by inhibiting the proteolytic activity of matrix metalloproteinases (MMPs). TIMP-1 also displays MMP-independent activities that influence the behavior of various cell types including neuronal plasticity, but the underlying molecular mechanisms remain mostly unknown. The trans-membrane receptor low-density lipoprotein receptor-related protein-1 (LRP-1) consists of a large extracellular chain with distinct ligand-bindi… Show more
“…T1-F12A and T1-K47A were associated with DII about 10 times faster than with DIV, while they dissociated with DII slower compared to DIV (Table 2). The measured association ( k
on ) and dissociation ( k
off ) rates were similar to those previously obtained for wild-type TIMP-1 6 . Our SPR data demonstrated that the lack of neurite outgrowth inhibition could not be explained by a difference of affinity towards LRP-1 between the mutants and T1-WT.Figure 5Effect of TIMP-1 mutants on neurite outgrowth.…”
The tissue inhibitor of metalloproteinases-1 (TIMP-1) exerts inhibitory activity against matrix metalloproteinases and cytokine-like effects. We previously showed that TIMP-1 reduces neurite outgrowth in mouse cortical neurons and that this cytokine-like effect depends on TIMP-1 endocytosis mediated by the low-density lipoprotein receptor-related protein-1 (LRP-1). To gain insight into the interaction between TIMP-1 and LRP-1, we considered conformational changes that occur when a ligand binds to its receptor. TIMP-1 conformational changes have been studied using biomolecular simulations, and our results provide evidence for a hinge region that is critical for the protein movement between the N- and C-terminal TIMP-1 domains. In silico mutants have been proposed on residues F12 and K47, which are located in the hinge region. Biological analyses of these mutants show that F12A or K47A mutation does not alter MMP inhibitory activity but impairs the effect of TIMP-1 on neurite outgrowth. Interestingly, these mutants bind to LRP-1 but are not endocytosed. We conclude that the intrinsic dynamics of TIMP-1 are not involved in its binding to LRP-1 but rather in the initiation of endocytosis and associated biological effects.
“…T1-F12A and T1-K47A were associated with DII about 10 times faster than with DIV, while they dissociated with DII slower compared to DIV (Table 2). The measured association ( k
on ) and dissociation ( k
off ) rates were similar to those previously obtained for wild-type TIMP-1 6 . Our SPR data demonstrated that the lack of neurite outgrowth inhibition could not be explained by a difference of affinity towards LRP-1 between the mutants and T1-WT.Figure 5Effect of TIMP-1 mutants on neurite outgrowth.…”
The tissue inhibitor of metalloproteinases-1 (TIMP-1) exerts inhibitory activity against matrix metalloproteinases and cytokine-like effects. We previously showed that TIMP-1 reduces neurite outgrowth in mouse cortical neurons and that this cytokine-like effect depends on TIMP-1 endocytosis mediated by the low-density lipoprotein receptor-related protein-1 (LRP-1). To gain insight into the interaction between TIMP-1 and LRP-1, we considered conformational changes that occur when a ligand binds to its receptor. TIMP-1 conformational changes have been studied using biomolecular simulations, and our results provide evidence for a hinge region that is critical for the protein movement between the N- and C-terminal TIMP-1 domains. In silico mutants have been proposed on residues F12 and K47, which are located in the hinge region. Biological analyses of these mutants show that F12A or K47A mutation does not alter MMP inhibitory activity but impairs the effect of TIMP-1 on neurite outgrowth. Interestingly, these mutants bind to LRP-1 but are not endocytosed. We conclude that the intrinsic dynamics of TIMP-1 are not involved in its binding to LRP-1 but rather in the initiation of endocytosis and associated biological effects.
“…Other metalloproteinases currently known to be endocytosed by LRP1 are MMP-9 [60], MMP-9-TIMP-1 complexes [61], MMP-2-thrombospondin 2 complexes [62], proMMP-2-TIMP-2 complexes [63], ADAMTS-4 [64] and ADAMTS-5 [65]. In addition, TIMP-1 [66], TIMP-2 [67] and TIMP-3 [68] can be endocytosed by LRP1. The rate of their endocytosis varies depending on their affinities for LRP1 [64].…”
Section: Regulation Of Metalloproteinases and Timps By Lrp1mentioning
Matrix metalloproteinases (MMPs) and adamalysin-like metalloproteinase with thrombospondin motifs (ADAMTSs) belong to the metzincin superfamily of metalloproteinases and they play key roles in extracellular matrix catabolism, activation and inactivation of cytokines, chemokines, growth factors, and other proteinases at the cell surface and within the extracellular matrix. Their activities are tightly regulated in a number of ways, such as transcriptional regulation, proteolytic activation and interaction with tissue inhibitors of metalloproteinases (TIMPs). Here, we highlight recent studies that have illustrated novel mechanisms regulating the extracellular activity of these enzymes. These include allosteric activation of metalloproteinases by molecules that bind outside the active site, modulation of location and activity by interaction with cell surface and extracellular matrix molecules, and endocytic clearance from the extracellular milieu by low-density lipoprotein receptor-related protein 1 (LRP1).
“…TIMP3 is sequestered in the ECM, whereas the other TIMPs are soluble in vivo . Not surprisingly, TIMP levels are also regulated by endocytosis by binding LRP-1, demonstrating that endocytic mechanisms play an important role in regulating metalloproteinase activity (24, 25). …”
Section: Members Of the Metalloproteinase Familymentioning
Myeloid cells have diverse roles in regulating immunity, inflammation, and extracellular matrix (ECM) turnover. To accomplish these tasks, myeloid cells carry an arsenal of metalloproteinases, which include the matrix metalloproteinases (MMPs) and the adamalysins. These enzymes have diverse substrate repertoires, and are thus involved in mediating proteolytic cascades, cell migration and cell signaling. Dysregulation of metalloproteinases contributes to pathogenic processes, including inflammation, fibrosis and cancer. Metalloproteinases also have important non-proteolytic functions in controlling cytoskeletal dynamics during macrophage fusion and enhancing transcription to promote anti-viral immunity. This review highlights the diverse contributions of metalloproteinases to myeloid cell functions.
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