The process of cancer progression involves the action of multiple proteolytic systems, among which the family of matrix metalloproteinases (MMPs) play a pivotal role. The MMPs evolved to accomplish their proteolytic tasks in multiple cellular and tissue microenvironments including lipid rafts by incorporation and deletions of specific structural domains. The membrane typeMMPs (MT-MMPs) incorporated membrane anchoring domains that display these proteases at the cell surface, and thus they are optimal pericellular proteolytic machines. Two members of the MT-MMP subfamily, MMP-17 (MT4-MMP) and MMP-25 (MT6-MMP), are anchored to the plasma membrane via a glycosyl-phosphatidyl inositol (GPI) anchor, which confers these enzymes a unique set of regulatory and functional mechanisms that separates them from the rest of the MMP family. Discovered almost a decade ago, the body of work on GPI-MT-MMPs today is still surprisingly limited when compared to other MT-MMPs. However, new evidence shows that the GPI-MT-MMPs are highly expressed in human cancer, where they are associated with progression. Accumulating biochemical and functional evidence also highlights their distinct properties. In this review, we summarize the structural, biochemical, and biological properties of GPI-MT-MMPs and present an overview of their expression and role in cancer. We further discuss the potential implications of GPI-anchoring for enzyme function. Finally, we comment on the new scientific challenges that lie ahead to better understand the function and role in cancer of these intriguing but yet unique MMPs.

It has become a current social trend for women to delay childbearing. However, the quality of oocytes from older females is compromised and the pregnancy rate of older women is lower. With the increased rate of delayed childbearing, it is becoming more and more crucial to understand the mechanisms underlying the compromised quality of oocytes from older women, including mitochondrial dysfunctions, aneuploidy and epigenetic changes. Establishing proper epigenetic modifications during oogenesis and early embryo development is an important aspect in reproduction. The reprogramming process may be influenced by external and internal factors that result in improper epigenetic changes in germ cells. Furthermore, germ cell epigenetic changes might be inherited by the next generations. In this review, we briefly summarise the effects of ageing on oocyte quality. We focus on discussing the relationship between ageing and epigenetic modifications, highlighting the epigenetic changes in oocytes from advanced-age females and in post-ovulatory aged oocytes as well as the possible underlying mechanisms.

MMP25 (MT6-MMP) is one of the two glycosylphosphatidylinositol-anchored matrix metalloproteinases (MMPsThe matrix metalloproteinases (MMPs) 2 are multidomain, multifunctional zinc-dependent endopeptidases, which have been associated with the pathogenesis of a variety of human diseases, including cancer (1, 2). The MMP family includes secreted and membrane-anchored proteases (3), and thus they are mediators of proteolysis in the pericellular space and at the cell surface. The membrane-type MMP (MT-MMP) subfamily includes six members, four of which are anchored to the plasma membrane via a transmembrane domain (MMP14, MMP15, MMP16, and MMP24, also referred to as MT1-, MT2-, MT3-, and MT5-MMP, respectively) and two of which are membrane-anchored via a glycosylphosphatidylinositol (GPI) moiety (MMP17 and MMP25, referred to as MT4-and MT6-MMP, respectively) (4, 5). Although there is a significant amount of information on the transmembrane MT-MMPs, little is known about the properties and functions of GPIanchored MT-MMPs.MT6-MMP was originally cloned from human leukocytes (6) and from a fetal liver cDNA library (7). In human normal tissues, MT6-MMP mRNA is predominantly expressed in leukocytes (polymorphonuclear cells and monocytes) but is also detected in lung and spleen (6 -8). Because of its abundance in leukocytes, MT6-MMP is also known as leukolysin (6). Functional studies with a recombinant catalytic domain showed that MT6-MMP can degrade various extracellular matrix components, including type IV collagen, gelatin, fibrin, fibronectin, chondroitin sulfate proteoglycan, and dermatan sulfate proteoglycan (9), suggesting that MT6-MMP may contribute to pericellular extracellular matrix degradation. MT6-MMP was also shown to inactivate ␣ 1 -proteinase inhibitor (10) and thus may play a role in inflammation (11), consistent with its high expression in leukocytes.Several transmembrane MT-MMPs initiate a cascade of zymogen activation at the cell surface by promoting the activation of pro-MMP-2 (5). Some MT-MMPs can also partner with members of the tissue inhibitors of metalloproteinase (TIMP) family to accomplish pro-MMP-2 activation. This process, which has been demonstrated with MT1-MMP and MT3-MMP, involves the generation of a ternary complex on the cell

Genomic sequencing and structural genomics produced a vast amount of sequence and structural data, creating an opportunity for structure-function analysis in silico [Radivojac P, et al. (2013) Nat Methods 10(3):221-227]. Unfortunately, only a few large experimental datasets exist to serve as benchmarks for functionrelated predictions. Furthermore, currently there are no reliable means to predict the extent of functional similarity among proteins. Here, we quantify structure-function relationships among three phylogenetic branches of the matrix metalloproteinase (MMP) family by comparing their cleavage efficiencies toward an extended set of phage peptide substrates that were selected from ∼64 million peptide sequences (i.e., a large unbiased representation of substrate space). The observed second-order rate constants [k (obs) ] across the substrate space provide a distance measure of functional similarity among the MMPs. These functional distances directly correlate with MMP phylogenetic distance. There is also a remarkable and near-perfect correlation between the MMP substrate preference and sequence identity of 50-57 discontinuous residues surrounding the catalytic groove. We conclude that these residues represent the specificity-determining positions (SDPs) that allowed for the expansion of MMP proteolytic function during evolution. A transmutation of only a few selected SDPs proximal to the bound substrate peptide, and contributing the most to selectivity among the MMPs, is sufficient to enact a global change in the substrate preference of one MMP to that of another, indicating the potential for the rational and focused redesign of cleavage specificity in MMPs.protease | specificity-determining positions | MMPs A paramount objective of biological research is to understand how sequence encodes function. Previously, functional regions in proteins were identified using large-scale mutagenesis (e.g., alanine scanning) (1). More recently, our insights are largely gained by computational approaches aimed at comparing sequences and structures of large protein sets across multiple genomes. The vast increase in the number of available sequences makes it possible to compare homology between sequences from genome projects to proteins of known structure and function and, as a result, identify functional similarities in silico (2-4). Because the global fold of most ordered proteins can be reliably predicted (5, 6) and because the catalytic residues of most classes of enzymes are either known or can be inferred (7,8), protein sequences can now be directly used to elucidate and classify major protein functions (9-12), and are even being extended to predict enzyme substrates (13).However, such classifications fail to explain the specialization and expansion of function that is required for organismal plasticity, complexity, and adaptability, all of which are normally driven by gene duplications and subsequent divergence. Computational approaches aimed at identifying functional distinctions across protein families have pri...

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It is well known that MAPK plays pivotal roles in oocyte maturation, but the function of MEK (MAPK kinase) remains unknown. We have studied the expression, subcellular localization and functional roles of MEK during meiotic maturation of mouse oocytes. Firstly, we found that MEK1/2 phoshorylation (p-MEK1/2, indicative of MEK activation) was low in GV (germinal vesicle) stage, increased 2h after GVBD (germinal vesicle breakdown), and reached the maximum at metaphase II. Secondly, we found that P-MEK1/2 was restricted in the GV prior to GVBD. In prometaphase I and metaphase I, P-MEK1/2 was mainly associated with the spindle, especially with the spindle poles. At anaphase I and telophase I, p-MEK1/2 became diffusely distributed in the region between the separating chromosomes, and then became associated with the midbody. The association of p-MEK1/2 with spindle poles was further confirmed by its colocalization with the centrosomal proteins, gamma-tubulin and NuMA. Thirdly, we have investigated the possible functional role of MEK1/2 activation by intravenous administration and intrabursal injection of a specific MEK inhibitor, U0126, and by microinjection of MEK siRNA into oocytes. All these manipulations cause disorganized spindle poles and spindle structure, misaligned chromosomes and larger than normal polar bodies. Our results suggest that MEK1/2 may function as a centrosomal protein and may have roles in microtubule organization, spindle pole tethering and asymmetric division during mouse oocyte maturation.

Protein kinase C (PKC), the major cell target for tumor-promoting phorbol esters, plays a central role in signal transduction pathways. In many biological systems where Ca(2+) serves as a second messenger, regulatory control is mediated by PKC. The activation of PKC depends on its binding to RACK1 receptor, which is an intracellular protein anchor for activated PKC. We demonstrate that the conventional PKC (cPKC) isoforms, PKC-alpha, PKC-betaI, and PKC-betaII, as well as RACK1, are expressed in mouse oocytes (germinal vesicle [GV]) and mature eggs (metaphase II [MII]). In GV oocytes, PKC-alpha, PKC-betaII, and RACK1 were uniformly distributed in the cytoplasm, while PKC-betaI was localized in the cytoplasm and in the plasma membrane as well. Treatment of GV oocytes with the biologically active phorbol ester, 12-o-tetradecanoyl phorbol-13-acetate (TPA), resulted in a rapid translocation of the cytosolic PKC-alpha, but not PKC-betaI, PKC-betaII, or RACK1, to the plasma membrane. This was associated with inhibition of GV breakdown. In MII eggs (17 h post-hCG), PKC-alpha was uniformly distributed in the cytoplasm while PKC-betaI and -betaII were distributed in the cytoplasm and in the plasma membrane as well. Treatment with TPA resulted in a rapid translocation of PKC-alpha from the cytoplasm to the plasma membrane and a significant decrease of PKC-betaI throughout the cytoplasm, while it also remained in the cell periphery. No change in the distribution of PKC-betaII or RACK1 was observed. TPA also induced pronucleus formation. Physiological activation of MII eggs by sperm induced cortical granule exocytosis associated with significant translocation of PKC-alpha and -betaI, but not -betaII, to the plasma membrane. Overall, these results suggest a possible involvement of cPKC isoforms in the mechanism of mouse oocyte maturation and egg activation.

The integration of remote sensing, geographic information system, landscape ecology and statistical analysis methods was applied to study the urban thermal environment in Guangzhou. Normalized Difference Vegetation Index (NDVI), Normalized Difference Build-up Index (NDBI), Normalized Difference Barren Index (NDBaI) and Modified Normalized Difference Water Index (MNDWI) were used to analyze the relationships between land surface temperature (LST) and land use/land cover (LULC) qualitatively. The result revealed that, most urban built-up lands were located in the middle part, and high LST areas mostly and were in the middle and southern parts. Therefore, the urbanization and thermal environment in the middle and southern parts need to be determined. Land surface temperature increased with the density of urban built-up and barren land, but decreased with vegetation cover. The relationship between MNDWI and LST was found to be negative, which implied that pure water would decrease the surface temperature and the polluted water would increase the surface temperature. A multiple regression between LST and each indices as well as the elevation was created to elevate the urban thermal environment, which showed that NDVI, NDBI, NDBaI, MNDWI were effective indicators for quantifying LULC impacts on LST.