Regulation of MT1-MMP Activity through Its Association with ERMs

The role of inflammatory mediators and matrix metalloproteinases (MMPs) in the progression of osteoarthritis

Osteoarthritis (OA) is a chronic musculoskeletal disorder characterized by an imbalance between (synthesis) and catabolism (degradation) in altered homeostasis of articular cartilage mediated primarily by the innate immune system. OA degenerates the joints resulting in synovial hyperplasia, degradation of articular cartilage with damage of the structural and functional integrity of the cartilage extracellular matrix, subchondral sclerosis, osteophyte formation, and is characterized by chronic pain, stiffness, and loss of function. Inflammation triggered by factors like biomechanical stress is involved in the development of osteoarthritis. In OA apart from catabolic effects, anti-inflammatory anabolic processes also occur continually. There is also an underlying chronic inflammation present, not only in cartilage tissue but also within the synovium, which perpetuates tissue destruction of the OA joint. The consideration of inflammation in OA considers synovitis and/or other cellular and molecular events in the synovium during the progression of OA. In this review, we have presented the progression of joint degradation that results in OA. The critical role of inflammation in the pathogenesis of OA is discussed in detail along with the dysregulation within the cytokine networks composed of inflammatory and anti-inflammatory cytokines that drive catabolic pathways, inhibit matrix synthesis, and promote cellular apoptosis. OA pathogenesis, fluctuation of synovitis, and its clinical impact on disease progression are presented here along with the role of synovial macrophages in promoting inflammatory and destructive responses in OA. The role of interplay between different cytokines, structure, and function of their receptors in the inter-cellular signaling pathway is further explored. The effect of cytokines in the increased synthesis and release of matrix-decomposing proteolytic enzymes, such as matrix metalloproteinase (MMPs) and a disintegrin-like and metalloproteinase with thrombospondin motif (ADAMTS), is elaborated emphasizing the potential impact of MMPs on the chondrocytes, synovial cells, articular and periarticular tissues, and other immune system cells migrating to the site of inflammation. We also shed light on the pathogenesis of OA via oxidative damage particularly due to nitric oxide (NO) via its angiogenic response to inflammation. We concluded by presenting the current knowledge about the tissue inhibitors of metalloproteinases (TIMPs). Synthetic MMP inhibitors include zinc binding group (ZBG), non-ZBG, and mechanism-based inhibitors, all of which have the potential to be therapeutically beneficial in the treatment of osteoarthritis. Improving our understanding of the signaling pathways and molecular mechanisms that regulate the MMP gene expression, may open up new avenues for the creation of therapies that can stop the joint damage associated with OA.

Molecular Mechanisms Driven by MT4-MMP in Cancer Progression

MT4-MMP (or MMP-17) belongs to the membrane-type matrix metalloproteinases (MT-MMPs), a distinct subset of the MMP family that is anchored to the cell surface, in this case by a glycosylphosphatidylinositol (GPI) motif. Its expression in a variety of cancers is well documented. However, the molecular mechanisms by which MT4-MMP contributes to tumor development need further investigation. In this review, we aim to summarize the contribution of MT4-MMP in tumorigenesis, focusing on the molecular mechanisms triggered by the enzyme in tumor cell migration, invasiveness, and proliferation, in the tumor vasculature and microenvironment, as well as during metastasis. In particular, we highlight the putative substrates processed and signaling cascades activated by MT4-MMP that may underlie these malignancy processes and compare this with what is known about its role during embryonic development. Finally, MT4-MMP is a relevant biomarker of malignancy that can be used for monitoring cancer progression in patients as well as a potential target for future therapeutic drug development.

Cytoplasmic Tail of MT1-MMP: A Hub of MT1-MMP Regulation and Function

MT1-MMP (MMP-14) is a multifunctional protease that regulates ECM degradation, activation of other proteases, and a variety of cellular processes, including migration and viability in physiological and pathological contexts. Both the localization and signal transduction capabilities of MT1-MMP are dependent on its cytoplasmic domain that constitutes the final 20 C-terminal amino acids, while the rest of the protease is extracellular. In this review, we summarize the ways in which the cytoplasmic tail is involved in regulating and enacting the functions of MT1-MMP. We also provide an overview of known interactors of the MT1-MMP cytoplasmic tail and the functional significance of these interactions, as well as further insight into the mechanisms of cellular adhesion and invasion that are regulated by the cytoplasmic tail.

Novel Roles of MT1-MMP and MMP-2: Beyond the Extracellular Milieu

Matrix metalloproteinases (MMPs) are critical enzymes involved in a variety of cellular processes. MMPs are well known for their ability to degrade the extracellular matrix (ECM) and their extracellular role in cell migration. Recently, more research has been conducted on investigating novel subcellular localizations of MMPs and their intracellular roles at their respective locations. In this review article, we focus on the subcellular localization and novel intracellular roles of two closely related MMPs: membrane-type-1 matrix metalloproteinase (MT1-MMP) and matrix metalloproteinase-2 (MMP-2). Although MT1-MMP is commonly known to localize on the cell surface, the protease also localizes to the cytoplasm, caveolae, Golgi, cytoskeleton, centrosome, and nucleus. At these subcellular locations, MT1-MMP functions in cell migration, macrophage metabolism, invadopodia development, spindle formation and gene expression, respectively. Similar to MT1-MMP, MMP-2 localizes to the caveolae, mitochondria, cytoskeleton, nucleus and nucleolus and functions in calcium regulation, contractile dysfunction, gene expression and ribosomal RNA transcription. Our particular interest lies in the roles MMP-2 and MT1-MMP serve within the nucleus, as they may provide critical insights into cancer epigenetics and tumor migration and invasion. We suggest that targeting nuclear MT1-MMP or MMP-2 to reduce or halt cell proliferation and migration may lead to the development of new therapies for cancer and other diseases.

There and back again: Intracellular trafficking, release and recycling of matrix metalloproteinases

Matrix metalloproteinases are a family of zinc-dependent endopeptidases that are involved in a large variety of proteolytic processes in physiological and pathological scenarios, including immune cell surveillance, tissue homeostasis, or tumor cell metastasis. This is based on their ability to cleave a plethora of substrates that include components of the extracellular matrix, but also cell surface-associated and intracellular proteins. Accordingly, a tight regulatory web has evolved that closely regulates spatiotemporal activity of specific MMPs. An often underappreciated mechanism of MMP regulation involves their trafficking to and from specific subcellular sites that require MMP activity only for a certain period. In this review, we focus on the current knowledge of MMP intracellular trafficking, their secretion or surface exposure, as well as their recycling back from the cell surface. We discuss molecular mechanisms that enable these steps, in particular microtubule-dependent motility of vesicles that is driven by molecular motors and directed by vesicle regulatory proteins. Finally, we also point out open questions in the field of MMP motility that may become important in the future.

Emerging roles of MT-MMPs in embryonic development

Membrane-type matrix metalloproteinases (MT-MMPs) are cell membrane-tethered proteinases that belong to the family of the MMPs. Apart from their roles in degradation of the extracellular milieu, MT-MMPs are able to activate through proteolytic processing at the cell surface distinct molecules such as receptors, growth factors, cytokines, adhesion molecules, and other pericellular proteins. Although most of the information regarding these enzymes comes from cancer studies, our current knowledge about their contribution in distinct developmental processes occurring in the embryo is limited. In this review, we want to summarize the involvement of MT-MMPs in distinct processes during embryonic morphogenesis, including cell migration and proliferation, epithelial-mesenchymal transition, cell polarity and branching, axon growth and navigation, synapse formation, and angiogenesis. We also considered information about MT-MMP functions from studies assessed in pathological conditions and compared these data with those relevant for embryonic development.

HMGB1-RAGE-moesin axis may be indicted for acne vulgaris

BACKGROUND

High-mobility group box 1 (HMGB1)-receptor for advanced glycation end (RAGE)-moesin axis could be implicated in induction of inflammation. However, there is a scarcity in literature discussing the role of this axis in inflammatory skin disorders.

AIMS

The aim of the present study was to evaluate the serum levels of HMGB1 and moesin in patients with inflammatory acne vulgaris.

PATIENTS/METHODS

This comparative cross-sectional study included 66 inflammatory acne vulgaris patients classified according to Global Acne Grading System (GAGS) into three groups (22 patients each): mild, moderate, and severe acne vulgaris. In addition, 82 acne-free individuals were included as a control group. Serum HMGB 1 and moesin levels were measured using enzyme-linked immunosorbent assay kits.

RESULTS

High-mobility group box 1 and moe sin serum levels in acne patients were significantly higher than the levels in control subjects (p = 0.04, 0.0005 respectively). Serum levels of both markers in severe acne patients and in those with post-acne scarring were elevated when compared to the levels in the other groups, and however, this elevation was significant only for moesin levels. There was a significant positive correlation between the serum levels of HMGB1 and moesin in the studied patient's sample (r = 0.3079, p = 0.011).

CONCLUSION

High-mobility group box 1-receptor for advanced glycation end-moesin axis may be implicated in acne vulgaris pathogenesis, and it may be a promising therapeutic target.

Bioactive Ent-Kaurane Diterpenes Oridonin and Irudonin Prevent Cancer Cells Migration by Interacting with the Actin Cytoskeleton Controller Ezrin

The ent-kaurane diterpene oridonin was reported to inhibit cell migration and invasion in several experimental models. However, the process by which this molecule exerts its anti-metastatic action has not been yet elucidated. In this article, we have investigated the anti-metastatic activity of Oridonin and of one homolog, Irudonin, with the aim to shed light on the molecular mechanisms underlying the biological activity of these ent-kaurane diterpenes. Cell-based experiments revealed that both compounds are able to affect differentiation and cytoskeleton organization in mouse differentiating myoblasts, but also to impair migration, invasion and colony formation ability of two different metastatic cell lines. Using a compound-centric proteomic approach, we identified some potential targets of the two bioactive compounds among cytoskeletal proteins. Among them, Ezrin, a protein involved in the actin cytoskeleton organization, was further investigated. Our results confirmed the pivotal role of Ezrin in regulating cell migration and invasion, and indicate this protein as a potential target for new anti-cancer therapeutic approaches. The interesting activity profile, the good selectivity towards cancer cells, and the lower toxicity with respect to Oridonin, all suggest that Irudonin is a very promising anti-metastatic agent.