抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Matrix metalloproteinases (MMPs), also designated matrixins, hydrolyze components of the extracellular matrix. These proteinases play a central role in many biological processes, such as embryogenesis, normal tissue remodeling, wound healing, and angiogenesis, and in diseases such as atheroma, arthritis, cancer, and tissue ulceration. Currently 23 MMP genes have been identified in humans, and most are multidomain proteins. This review describes the members of the matrixin family and discusses substrate specificity, domain structure and function, the activation of proMMPs, the regulation of matrixin activity by tissue inhibitors of metalloproteinases, and their pathophysiological implication.

Matrix metalloproteinases and tissue inhibitors of metalloproteinases: structure, function, and biochemistry.

▪ Abstract The matrix metalloproteinases (MMPs) constitute a multigene family of over 25 secreted and cell surface enzymes that process or degrade numerous pericellular substrates. Their targets include other proteinases, proteinase inhibitors, clotting factors, chemotactic molecules, latent growth factors, growth factor–binding proteins, cell surface receptors, cell-cell adhesion molecules, and virtually all structural extracellular matrix proteins. Thus MMPs are able to regulate many biologic processes and are closely regulated themselves. We review recent advances that help to explain how MMPs work, how they are controlled, and how they influence biologic behavior. These advances shed light on how the structure and function of the MMPs are related and on how their transcription, secretion, activation, inhibition, localization, and clearance are controlled. MMPs participate in numerous normal and abnormal processes, and there are new insights into the key substrates and mechanisms responsible for regula...

/pdf/how-matrix-metalloproteinases-regulate-cell-behavior-1ljn27ub20.pdf

How Matrix Metalloproteinases Regulate Cell Behavior

Autophagy is a major catabolic pathway by which eukaryotic cells degrade and recycle macromolecules and organelles. This pathway is activated under environmental stress conditions, during development and in various pathological situations. In this study, we describe the role of reactive oxygen species (ROS) as signaling molecules in starvation-induced autophagy. We show that starvation stimulates formation of ROS, specifically H2O2. These oxidative conditions are essential for autophagy, as treatment with antioxidative agents abolished the formation of autophagosomes and the consequent degradation of proteins. Furthermore, we identify the cysteine protease HsAtg4 as a direct target for oxidation by H2O2, and specify a cysteine residue located near the HsAtg4 catalytic site as a critical for this regulation. Expression of this regulatory mutant prevented the formation of autophagosomes in cells, thus providing a molecular mechanism for redox regulation of the autophagic process.

/pdf/reactive-oxygen-species-are-essential-for-autophagy-and-3pezt553nc.pdf

Reactive oxygen species are essential for autophagy and specifically regulate the activity of Atg4

Metastatic spread of cancer continues to be the greatest barrier to cancer cure. Understanding the molecular mechanisms of metastasis is crucial for the design and effective use of novel therapeutic strategies to combat metastases. One class of molecules that has been repeatedly implicated in metastasis is the matrix metalloproteinases (MMPs). In this review, we re-examine the evidence that MMPs are associated with metastasis and that they make a functional contribution to the process. Initially, it was believed that the major role of MMPs in metastasis was to facilitate the breakdown of physical barriers to metastasis, thus promoting invasion and entry into and out of blood or lymphatic vessels (intravasation, extravasation). However, recent evidence suggests that MMPs may have a more complex role in metastasis and that they may make important contributions at other steps in the metastatic process. Studies using intravital videomicroscopy, as well as experiments in which levels of MMPs or their inhibitors (tissue inhibitors of metalloproteinases [TIMPs]) are manipulated genetically or pharmacologically, suggest that MMPs are key regulators of growth of tumors, at both primary and metastatic sites. On the basis of this evidence, a new view of the functional role of MMPs in metastasis is presented, which suggests that MMPs are important in creating and maintaining an environment that supports the initiation and maintenance of growth of primary and metastatic tumors. Further clarification of the mechanisms by which MMPs regulate growth of primary and metastatic tumors will be important in the development of novel therapeutic strategies against metastases.

/pdf/changing-views-of-the-role-of-matrix-metalloproteinases-in-17khjxc5wu.pdf

Changing Views of the Role of Matrix Metalloproteinases in Metastasis

Human autophagins, a family of cysteine proteinases potentially implicated in cell degradation by autophagy.

We have identified a human placenta cDNA coding for a new member of the matrix metalloproteinase (MMP) family. The isolated cDNA encodes a polypeptide of 261 amino acids, the smallest MMP identified to date, which contains several structural features of MMPs including the signal sequence, the prodomain involved in enzyme latency, and the catalytic domain with the zinc-binding site. However, it lacks the hinge region and hemopexin-domain present in most MMPs. According to these structural characteristics, the human MMP described herein has been called matrilysin-2 (MMP-26), because it exclusively shares with matrilysin this minimal domain organization required for secretion, latency, and activity. The amino acid sequence of matrilysin-2 also contains a threonine residue adjacent to the Zn-binding site that has been defined as a specific feature of matrilysin. Chromosomal location of the matrilysin-2 gene showed that it maps to the short arm of chromosome 11, a location distinct to that of other MMP genes. Matrilysin-2 was expressed in Escherichia coli, and, after purification and refolding, the recombinant protein was found to degrade synthetic substrates commonly used for assaying MMPs. Furthermore, this protein hydrolyzed type IV collagen, fibronectin, fibrinogen, and gelatin, which indicated that matrilysin-2 is a potent enzyme with a wide substrate specificity. In addition, it was found that matrilysin-2 is able to activate progelatinase B. Proteolytic activity of matrilysin-2 against all of these substrates was abolished by synthetic inhibitors and by tissue inhibitors of metalloproteinases. Expression analysis revealed that matrilysin-2 is detected not only in placenta and uterus but is widely expressed in malignant tumors from different sources as well as in diverse tumor cell lines. These data together with its broad spectrum of proteolytic activity, suggest that matrilysin-2 may play a role in some of the tissue-remodeling events associated with tumor progression.

https://cancerres.aacrjournals.org/content/canres/60/17/4745.full.pdf

Matrilysin-2, a New Matrix Metalloproteinase Expressed in Human Tumors and Showing the Minimal Domain Organization Required for Secretion, Latency, and Activity

Differential Effects of Transforming Growth Factor-β on the Expression of Collagenase-1 and Collagenase-3 in Human Fibroblasts

A new member of the metalloproteinase inhibitor family of proteins has been cloned from a complementary DNA library derived from a human breast tumor. The isolated complementary DNA contains an open reading frame 633 base pairs long, encoding a polypeptide of 211 amino acids, which has been called tissue inhibitor of metalloproteinase 3 (TIMP-3). This protein displays low sequence similarity to the previously known human TIMPs but shows a high degree of similarity with chicken inhibitor of metalloproteinase 3, a recently described metalloproteinase inhibitor stimulated during oncogenic transformation of chicken fibroblasts and with the ability to promote some phenotypic properties of transformed cells. Northern blot analysis of RNA from human tissues revealed that the TIMP-3 gene is expressed in placenta and uterus but not in liver and ovary. In addition, TIMP-3 transcripts were detected in all breast carcinomas examined. On the basis of these expression data in breast tumors, together with its high degree of structural homology with chicken inhibitor of metalloproteinase 3, a possible role for human TIMP-3 in the regulation of connective tissue turnover and remodeling is proposed.

https://cancerres.aacrjournals.org/content/canres/54/8/2091.full.pdf

Structure and Expression in Breast Tumors of Human TIMP-3, a New Member of the Metalloproteinase Inhibitor Family'

Collagenase-3 (MMP-13) is a recently identified member of the human matrix metalloproteinase gene family that is expressed in breast carcinomas and in articular cartilage from arthritic patients Here, we have studied the cellular origin of this enzyme in breast carcinomas by in situ RNA hybridization, and we found that collagenase-3 is expressed by stromal cells immediately adjacent to epithelial tumor cells but not by the tumor cells themselves; nor is it expressed by the normal breast glandular epithelium Consistent with this observation, coculture experiments using human fibroblasts and MCF-7 breast cancer cells revealed that conditioned medium from breast cancer cells stimulated the fibroblastic expression of collagenase-3 mRNA In contrast, no stimulatory effect was observed when medium from fibroblast cells was added to breast cancer cells These results strongly suggest that transcription of collagenase-3 in stromal cells is activated by diffusible factors released from epithelial breast cancer cells A survey of a series of cytokines and growth factors known for their ability to induce collagenase-3 expression in human fibroblasts identified interleukin-1α and interleukin-1β as potential candidates for inducing the expression of this MMP gene in breast carcinomas According to these results, collagenase-3 should be included among the molecular factors that are detected during the stromal reaction to invasive breast cancer and that, by concerted action, may be essential for tumor growth and progression

https://cancerres.aacrjournals.org/content/canres/57/21/4882.full.pdf

José A. Uría

Papers

Human autophagins, a family of cysteine proteinases potentially implicated in cell degradation by autophagy.

Matrilysin-2, a New Matrix Metalloproteinase Expressed in Human Tumors and Showing the Minimal Domain Organization Required for Secretion, Latency, and Activity

Differential Effects of Transforming Growth Factor-β on the Expression of Collagenase-1 and Collagenase-3 in Human Fibroblasts

Structure and Expression in Breast Tumors of Human TIMP-3, a New Member of the Metalloproteinase Inhibitor Family'

Regulation of Collagenase-3 Expression in Human Breast Carcinomas Is Mediated by Stromal-Epithelial Cell Interactions