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-binding domains that interact with numerous ligands including TIMP-2 and TIMP-3 and a short transmembrane chain with intracellular motifs that allow endocytosis and confer signaling properties to LRP-1. We addressed TIMP-1 interaction with recombinant ligand-binding domains of LRP-1 expressed by CHO cells for endocytosis study, or linked onto sensor chips for surface plasmon resonance analysis. Primary cortical neurons bound and internalized endogenous TIMP-1 through a mechanism mediated by LRP-1. This resulted in inhibition of neurite outgrowth and increased growth cone volume. Using a mutated inactive TIMP-1 variant we showed that TIMP-1 effect on neurone morphology was independent of its MMP inhibitory activity. We conclude that TIMP-1 is a new ligand of LRP-1 and we highlight a new example of its MMP-independent, cytokine-like functions.
Highlights
The four tissue inhibitors of metalloproteinases (TIMP-1–4) inhibit the proteolytic activity of matrix metalloproteinases (MMPs) and together constitute the principal regulators of the pericellular environment in physiological and pathological situations [1]
We have demonstrated that CHO cells overexpressing lipoprotein receptor-related protein-1 (LRP-1) mini-receptors bind and internalize Tissue inhibitor of metalloproteinases-1 (TIMP-1)
We have shown that primary cortical neurons from murine embryos endocytose TIMP-1 by a mechanism dependent on LRP-1
Summary
The four tissue inhibitors of metalloproteinases (TIMP-1–4) inhibit the proteolytic activity of matrix metalloproteinases (MMPs) and together constitute the principal regulators of the pericellular environment in physiological and pathological situations [1]. Of their MMP inhibitory properties, TIMPs elicit signaling pathways through binding to membrane receptors that lead for instance to regulation of cell growth and apoptosis [2,3]. We recently demonstrated that LRP-1 knockdown inhibited migration and invasive capacities of carcinoma cells, and identified the extracellular signal regulated protein kinases (ERK) and c-Jun N-terminal kinases (JNK) as the main LRP-1 molecular relays to regulate focal adhesion disassembly in malignant cells [16,17]
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