Alicia R. Folgueras

Accelerated ageing in mice deficient in Zmpste24 protease is linked to p53 signalling activation.

Zmpste24 (also called FACE-1) is a metalloproteinase involved in the maturation of lamin A (Lmna), an essential component of the nuclear envelope. Both Zmpste24- and Lmna-deficient mice exhibit profound nuclear architecture abnormalities and multiple histopathological defects that phenocopy an accelerated ageing process. Similarly, diverse human progeroid syndromes are caused by mutations in ZMPSTE24 or LMNA genes. To elucidate the molecular mechanisms underlying these devastating diseases, we have analysed the transcriptional alterations occurring in tissues from Zmpste24-deficient mice. We demonstrate that Zmpste24 deficiency elicits a stress signalling pathway that is evidenced by a marked upregulation of p53 target genes, and accompanied by a senescence phenotype at the cellular level and accelerated ageing at the organismal level. These phenotypes are largely rescued in Zmpste24-/-Lmna+/- mice and partially reversed in Zmpste24-/-p53-/- mice. These findings provide evidence for the existence of a checkpoint response activated by the nuclear abnormalities caused by prelamin A accumulation, and support the concept that hyperactivation of the tumour suppressor p53 may cause accelerated ageing.

Matrix metalloproteinases: Evolution, gene regulation and functional analysis in mouse models

Matrix metalloproteinases (MMPs) are a large family of zinc-endopeptidases which play important roles in multiple physiological and pathological processes. These enzymes are widely distributed in all kingdoms of life and have likely evolved from a single-domain protein which underwent successive rounds of duplication, gene fusion and exon shuffling events to generate the multidomain architecture and functional diversity currently exhibited by MMPs. Proper regulation of these enzymes is required to prevent their unwanted activity in a variety of disorders, including cancer, arthritis and cardiovascular diseases. Multiple hormones, cytokines and growth factors are able to induce MMP expression, although the tissue specificity of the diverse family members is mainly achieved by the combination of different transcriptional control mechanisms. The integration of multiple signaling pathways, coupled with the cooperation between several cis-regulatory elements found at the MMP promoters facilitates the strict spatiotemporal control of MMP transcriptional activity. Additionally, epigenetic mechanisms, such as DNA methylation or histone acetylation, may also contribute to MMP regulation. Likewise, post-transcriptional regulatory processes including mRNA stability, protein translational efficiency, and microRNA-based mechanisms have been recently described as modulators of MMP gene expression. Parallel studies have led to the identification of MMP polymorphisms and mutations causally implicated in the development of different genetic diseases. These genomic analyses have been further extended through the generation of animal models of gain- or loss-of-function for MMPs which have allowed the identification of novel functions for these enzymes and the establishment of causal relationships between MMP dysregulation and development of different human diseases. Further genomic studies of MMPs, including functional analysis of gene regulation and generation of novel animal models will help to answer the multiple questions still open in relation to a family of enzymes which strongly influence multiple events in life and disease.

Membrane-bound serine protease matriptase-2 (Tmprss6) is an essential regulator of iron homeostasis

Proteolytic events at the cell surface are essential in the regulation of signal transduction pathways. During the past years, the family of type II transmembrane serine proteases (TTSPs) has acquired an increasing relevance because of their privileged localization at the cell surface, although our current understanding of the biologic function of most TTSPs is limited. Here we show that matriptase-2 (Tmprss6), a recently described member of the TTSP family, is an essential regulator of iron homeostasis. Thus, Tmprss6(-/-) mice display an overt phenotype of alopecia and a severe iron deficiency anemia. These hematologic alterations found in Tmprss6(-/-) mice are accompanied by a marked up-regulation of hepcidin, a negative regulator of iron export into plasma. Likewise, Tmprss6(-/-) mice have reduced ferroportin expression in the basolateral membrane of enterocytes and accumulate iron in these cells. Iron-dextran therapy rescues both alopecia and hematologic alterations of Tmprss6(-/-) mice, providing causal evidence that the anemic phenotype of these mutant mice results from the blockade of intestinal iron export into plasma after dietary absorption. On the basis of these findings, we conclude that matriptase-2 activity represents a novel and relevant step in hepcidin regulation and iron homeostasis.

Matrix Metalloproteinase-8 Functions as a Metastasis Suppressor through Modulation of Tumor Cell Adhesion and Invasion

Collagenase-2 (matrix metalloproteinase-8, MMP-8) is an MMP mainly produced by neutrophils and associated with many inflammatory conditions. We have previously described that MMP-8 plays a protective role in cancer through its ability to regulate the inflammatory response induced by carcinogens. Moreover, it has been reported that experimental manipulation of the expression levels of this enzyme alters the metastatic behavior of human breast cancer cells. In this work, we have used mutant mice deficient in MMP-8 and syngenic melanoma and lung carcinoma tumor cells lines overexpressing this enzyme to further explore the putative antimetastatic potential of MMP-8. We report herein that MMP-8 prevents metastasis formation through the modulation of tumor cell adhesion and invasion. Thus, tumor cells overexpressing MMP-8 have an increased adhesion to extracellular matrix proteins, whereas their invasive ability through Matrigel is substantially reduced when compared with control cells. Analysis of MMP-8 in breast cancer patients revealed that the expression of this metalloproteinase by breast tumors correlates with a lower incidence of lymph node metastasis and confers good prognosis to these patients. On this basis, we propose that MMP-8 is a tumor protective factor, which also has the ability to reduce the metastatic potential of malignant cells in both mice and human.

Matriptase-2 (TMPRSS6): a proteolytic regulator of iron homeostasis

The family of membrane anchored serine proteases is increasingly being acknowledged as having critical physiological functions, exemplified recently by the discovery of the iron regulatory role of matriptase-2. This protease, encoded by TMRPSS6, has a specific role in hepcidin inhibition and iron absorption. In this review article, the authors discuss our current knowledge on this new and exciting issue. Maintaining the body’s levels of iron within precise boundaries is essential for normal physiological function. Alterations of these levels below or above the healthy limit lead to a systemic deficiency or overload in iron. The type-two transmembrane serine protease (TTSP), matriptase-2 (also known as TMPRSS6), is attracting significant amounts of interest due to its recently described role in iron homeostasis. The finding of this regulatory role for matriptase-2 was originally derived from the observation that mice deficient in this protease present with anemia due to elevated levels of hepcidin and impaired intestinal iron absorption. Further in vitro analysis has demonstrated that matriptase-2 functions to suppress bone morphogenetic protein stimulation of hepcidin transcription through cell surface proteolytic processing of the bone morphogenetic protein co-receptor hemojuvelin. Consistently, the anemic phenotype of matriptase-2 knockout mice is mirrored in humans with matripase-2 mutations. Currently, 14 patients with iron-refractory iron deficiency anemia (IRIDA) have been reported to harbor various genetic mutations that abrogate matriptase-2 proteolytic activity. In this review, after overviewing the membrane anchored serine proteases, in particular the TTSP family, we summarize the identification and characterization of matriptase-2 and describe its functional relevance in iron metabolism.

Diet-Induced Obesity and Reduced Skin Cancer Susceptibility in Matrix Metalloproteinase 19-Deficient Mice

ABSTRACT Matrix metalloproteinase 19 (MMP-19) is a member of the MMP family of endopeptidases that, in contrast to most MMPs, is widely expressed in human tissues under normal quiescent conditions. MMP-19 has been found to be associated with ovulation and angiogenic processes and is deregulated in diverse pathological conditions such as rheumatoid arthritis and cancer. To gain further insights into the in vivo functions of this protease, we have generated mutant mice deficient in Mmp19. These mice are viable and fertile and do not display any obvious abnormalities. However, Mmp19-null mice develop a diet-induced obesity due to adipocyte hypertrophy and exhibit decreased susceptibility to skin tumors induced by chemical carcinogens. Based on these results, we suggest that this enzyme plays an in vivo role in some of the tissue remodeling events associated with adipogenesis, as well as in pathological processes such as tumor progression.

Earlier Onset of Tumoral Angiogenesis in Matrix Metalloproteinase-19–Deficient Mice

Among matrix metalloproteinases (MMP), MMP-19 displays unique structural features and tissue distribution. In contrast to most MMPs, MMP-19 is expressed in normal human epidermis and down-regulated during malignant transformation and dedifferentiation. The contribution of MMP-19 during tumor angiogenesis is presently unknown. In an attempt to give new insights into MMP-19 in vivo functions, angiogenic response of mutant mice lacking MMP-19 was analyzed after transplantation of murine malignant PDVA keratinocytes and after injection of Matrigel supplemented with basic fibroblast growth factor. In situ hybridization and immunohistochemical analysis revealed that MMP-19 is produced by host mesenchymal cells but not by endothelial capillary cells or CD11b-positive inflammatory cells. Based on a new computer-assisted method of quantification, we provide evidence that host MMP-19 deficiency was associated with an increased early angiogenic response. In addition, increased tumor invasion was observed in MMP-19-/- mice. We conclude that, in contrast to most MMPs that promote tumor progression, MMP-19 is a negative regulator of early steps of tumor angiogenesis and invasion. These data highlight the requirement to understand the individual functions of each MMP to improve anticancer strategies.

Collagenase-2 Deficiency or Inhibition Impairs Experimental Autoimmune Encephalomyelitis in Mice

Matrix metalloproteinases (MMPs) have been implicated in a variety of human diseases, including neuroimmunological disorders such as multiple sclerosis. However, the recent finding that some MMPs play paradoxical protective roles in these diseases has made necessary the detailed study of the specific function of each family member in their pathogenesis. To determine the relevance of collagenase-2 (MMP-8) in experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis, we have performed two different analyses involving genetic and biochemical approaches. First, we have analyzed the development of EAE in mutant mouse deficient in MMP-8, with the finding that the absence of this proteolytic enzyme is associated with a marked reduction in the clinical symptoms of EAE. We have also found that MMP-8-/- mice exhibit a marked reduction in central nervous system-infiltrating cells and demyelinating lesions. As a second approach, we have carried out a pharmacological inhibition of MMP-8 with a selective inhibitor against this protease (IC50 = 0.4 nm). These studies have revealed that the administration of the MMP-8 selective inhibitor to mice with EAE also reduces the severity of the disease. Based on these findings, we conclude that MMP-8 plays an important role in EAE development and propose that this enzyme may be a novel therapeutic target in human neuro-inflammatory diseases such as multiple sclerosis.

Metalloproteinase MT5-MMP is an essential modulator of neuro-immune interactions in thermal pain stimulation

Peripheral interactions between nociceptive fibers and mast cells contribute to inflammatory pain, but little is known about mechanisms mediating neuro-immune communication. Here we show that metalloproteinase MT5-MMP (MMP-24) is an essential mediator of peripheral thermal nociception and inflammatory hyperalgesia. We report that MT5-MMP is expressed by CGRP-containing peptidergic nociceptors in dorsal root ganglia and that Mmp24-deficient mice display enhanced sensitivity to noxious thermal stimuli under basal conditions. Consistently, mutant peptidergic sensory neurons hyperinnervate the skin, a phenotype that correlates with changes in the regulated cleavage of the cell-cell adhesion molecule N-cadherin. In contrast to basal nociception, Mmp24−/− mice do not develop thermal hyperalgesia during inflammation, a phenotype that appears associated with alterations in N-cadherin-mediated cell-cell interactions between mast cells and sensory fibers. Collectively, our findings demonstrate an essential role of MT5-MMP in the development of dermal neuro-immune synapses and suggest that this metalloproteinase may be a target for pain control.

Nitric oxide elicits functional MMP-13 protein-tyrosine nitration during wound repair

Nitric oxide (NO) plays a critical role in wound healing, in part by promoting angiogenesis. However, the precise repair pathways affected by NO are not well defined. We now show that NO regulates matrix metalloproteinase‐13 (MMP‐13) release during wound repair. We find that normally MMP‐13 is kept inside endothelial cells by an association with caveo‐lin‐1. However, nitration of MMP‐13 on tyrosine residue Y338 causes it to dissociate from caveolin‐1 and be released from endothelial cells. We next explored the functional significance of MMP‐13 nitration in vivo. Skin injury increases nitration of MMP‐13 in mice. Skin wounds in inducible nitric oxide synthase knockout mice release less MMP‐13 and heal more slowly than skin wounds in wild‐type mice. Conversely, skin wounds in caveolin‐1 knockout mice have increased NO production, increased MMP‐13 nitration, and accelerated wound healing. Collectively, our data reveal a new pathway through which NO modulates wound repair: nitration of MMP‐13 promotes its release from endothelial cells, where it accelerates angiogenesis and wound healing.—Lizarbe, T. R., García‐Ram, C., Tarín, C., Saura, M., Calvo, E., López, J. A., López‐Otín, C., Folgueras, A. R., Lamas, S., Zaragoza, C. Nitric oxide elicits functional MMP‐13 protein‐tyrosine nitration during wound repair. FASEB J. 22, 3207–3215 (2008)