Invadolysin: a novel, conserved metalloprotease links mitotic structural rearrangements with cell migration

Margarete Heck (1959-2023): Cell biologist, geneticist, and incandescent social spark

Margarete M.S. Heck, professor of cell biology and genetics, University of Edinburgh, died peacefully at home amid her loving family under a blue moon on August 30, 2023, after a long journey with ovarian cancer.

Genes differentially expressed between pathogenic and non-pathogenic Entamoeba histolytica clones influence pathogenicity-associated phenotypes by multiple mechanisms

Recently, two genes involved in amoebic liver abscess formation in a mouse model were identified by their differential expression of non-pathogenic (A1np) and pathogenic (B2p) clones of the Entamoeba histolytica isolate HM:1-IMSS. While overexpression of a gene encoding the metallopeptidase EhMP8-2 reduces the virulence of the pathogenic clone B2p, overexpression of the gene ehi_127670 (ehhp127), encoding a hypothetical protein, increases the virulence of the non-pathogenic clone A1np, while silencing this gene in the pathogenic B2p reduces virulence. To understand the role of both molecules in determining the pathogenicity of E. histolytica, silencing, and overexpression transfectants were characterized in detail. Silencing of ehmp8-2, of the homologous gene ehmp8-1, or both in non-pathogenic A1np trophozoites significantly altered the transcript levels of 347, 216, and 58 genes, respectively. This strong change in the expression profiles caused by the silencing of ehmp8-1 and ehmp8-2 implies that these peptidases regulate the expression of numerous genes. Consequently, numerous phenotypic characteristics, including cytopathic, hemolytic, and cysteine peptidase activity, were altered in response to their silencing. Silencing of ehhp127 in pathogenic B2p trophozoites did not affect the expression of other genes, whereas its overexpression in non-pathogenic A1np trophozoites results in an altered expression of approximately 140 genes. EhHP127 is important for trophozoite motility, as its silencing reduces, while its overexpression enhances movement activity. Interestingly, the specific silencing of ehhp127 also significantly affects cytopathic, cysteine peptidase, and hemolytic activities. All three molecules characterized in this study, namely EhMP8-1, EhMP8-2, and EhHP127, are present in amoeba vesicles. The results show that ehmp8-2 and ehhp127 are not only differentially expressed between pathogenic and non-pathogenic amoebae, but that they also significantly affect amoeba pathogenicity-associated phenotypes by completely different mechanisms. This observation suggests that the regulation of amoeba pathogenicity is achieved by a complex network of molecular mechanisms rather than by single factors.

Modulation of peptidases by 2,4-diamine-quinazoline derivative induces cell death in the amitochondriate parasite Trichomonas vaginalis

Trichomonas vaginalis is an amitochondriate protozoan and the agent of human trichomoniasis, the most prevalent non-viral sexually transmitted infection (STI) in the world. In this study we showed that 2,4-diamine-quinazoline derivative compound (PH100) kills T. vaginalis. PH100 showed activity against fresh clinical and American Type Culture Collection (ATCC) T. vaginalis isolates with no cytotoxicity against cells (HMVI, 3T3-C1 and VERO) and erythrocytes. In addition, PH100 showed synergistic action with metronidazole, indicating that these compounds act by different mechanisms. When investigating the mechanism of action of PH100 to ATCC 30236, apoptosis-like characteristics were observed, such as phosphatidylserine exposure, membrane alterations, and modulation of gene expression and activity of peptidases related to apoptosis. The apoptosis-like cell death features were not observed for the fresh clinical isolate treated with PH100 revealing distinct profiles. Our data revealed the heterogeneity among T. vaginalis isolates and contribute with the understanding of mechanisms of cell death in pathogenic eukaryotic organisms without mitochondria.

Genotype-phenotype association and variant characterization in Diamond-Blackfan anemia caused by pathogenic variants in RPL35A

Diamond Blackfan anemia (DBA) is predominantly an autosomal dominant inherited red cell aplasia primarily caused by pathogenic germline variants in ribosomal protein genes. DBA due to pathogenic RPL35A variants has been associated with large 3q29 deletions and phenotypes not common in DBA. We conducted a multi-institutional genotypephenotype study of 45 patients with DBA associated with pathogenic RPL35A germline variants and curated the variant data on 21 additional cases from the literature. Genotype-phenotype analyses were conducted comparing patients with large deletions versus all other pathogenic variants in RPL35A. Twenty-two of the 45 cases had large deletions in RPL35A. After adjusting for multiple tests, a statistically significant association was observed between patients with a large deletion and steroid-resistant anemia, neutropenia, craniofacial abnormalities, chronic gastrointestinal problems, and intellectual disabilities (P<0.01) compared with all other pathogenic variants. Non-large deletion pathogenic variants were spread across RPL35Awith no apparent hot spot and 56% of the individual family variants were observed more than once. In this, the largest known study of DBA patients with pathogenic RPL35A variants, we determined that patients with large deletions have a more severe phenotype that is clinically different from those with non-large deletion variants. Genes of interest also deleted in the 3q29 region that could be associated with some of these phenotypic features include LMLN and IQCG. Management of DBA due to large RPL35A deletions may be challenging due to complex problems and require comprehensive assessments by multiple specialists including immunological, gastrointestinal, and developmental evaluations to provide optimal multidisciplinary care.

Coactosin Phosphorylation Controls Entamoeba histolytica Cell Membrane Protrusions and Cell Motility

Invasion of the colon wall by Entamoeba histolytica during amoebic dysentery entails migration of trophozoites through tissue layers that are rich in extracellular matrix. Transcriptional silencing of the E. histolytica surface metalloprotease EhMSP-1 produces hyperadherent less-motile trophozoites that are deficient in forming invadosomes. Reversible protein phosphorylation is often implicated in regulation of cell motility and invadosome formation. To identify such intermediaries of the EhMSP-1-silenced phenotype, here we compared the phosphoproteomes of EhMSP-1-silenced and vector control trophozoites by using quantitative tandem mass spectrometry-based proteomics. Six proteins were found to be differentially phosphorylated in EhMSP-1-silenced and control cells, including EhCoactosin, a member of the ADF/cofilin family of actin-binding proteins, which was more frequently phosphorylated at serine 147. Regulated overexpression of wild-type, phosphomimetic, and nonphosphorylatable EhCoactosin variants was used to test if phosphorylation functions in control of E. histolytica actin dynamics. Each of the overexpressed proteins colocalized with F-actin during E. histolytica phagocytosis. Nonetheless, trophozoites overexpressing an EhCoactosin phosphomimetic mutant formed more and poorly coordinated cell membrane protrusions compared to those in control or cells expressing a nonphosphorylatable mutant, while trophozoites overexpressing nonphosphorylatable EhCoactosin were significantly more motile within a model of mammalian extracellular matrix. Therefore, although EhCoactosin's actin-binding ability appeared unaffected by phosphorylation, EhCoactosin phosphorylation helps to regulate amoebic motility. These data help to understand the mechanisms underlying altered adherence and motility in EhMSP-1-silenced trophozoites and lay the groundwork for identifying kinases and phosphatases critical for control of amoebic invasiveness.IMPORTANCE Invasive amoebiasis, caused by the intestinal parasite Entamoeba histolytica, causes life-threatening diarrhea and liver abscesses, but, for unknown reasons, only approximately 10% of E. histolytica infections become symptomatic. A key requirement of invasion is the ability of the parasite to migrate through tissue layers. Here, we systematically looked for differences in protein phosphorylation between control parasites and a previously identified hyperadherent E. histolytica cell line that has reduced motility. We identified EhCoactosin, an actin-binding protein not previously known to be phosphoregulated, as one of the differentially phosphorylated proteins in E. histolytica and demonstrated that EhCoactosin phosphorylation functions in control of cell membrane dynamics and amoebic motility. This and the additional differentially phosphorylated proteins reported lay the groundwork for identifying kinases and phosphatases that regulate tissue invasiveness.

The conserved metalloprotease invadolysin is present in invertebrate haemolymph and vertebrate blood

We identified invadolysin, a novel essential metalloprotease, for functions in chromosome structure, cell proliferation and migration. Invadolysin also plays an important metabolic role in insulin signalling and is the only protease known to localise to lipid droplets, the main lipid storage organelle in the cell. In silico examination of the protein sequence of invadolysin predicts not only protease and lipase catalytic motifs, but also post-translational modifications and the secretion of invadolysin. Here we show that the protease motif of invadolysin is important for its role in lipid accumulation, but not in glycogen accumulation. The lipase motif does not appear to be functionally important for the accumulation of lipids or glycogen. Post-translational modifications likely contribute to modulating the level, localisation or activity of invadolysin. We identified a secreted form of invadolysin in the soluble fraction of invertebrate hemolymph (where we observe sexually dimorphic forms) and also vertebrate plasma, including in the extracellular vesicle fraction. Biochemical analysis for various post-translational modifications demonstrated that secreted invadolysin is both N- and O-glycosylated, but not apparently GPI-linked. The discovery of invadolysin in the extracellular milieu suggests a role for invadolysin in normal organismal physiology.

Summary: In this study, we show that the conserved metalloprotease invadolysin is present in invertebrate hemolymph and vertebrate blood, suggesting the protein may function in organismal physiology.

A metalloprotease produced by larval Schistosoma mansoni facilitates infection establishment and maintenance in the snail host by interfering with immune cell function

Metalloproteases (MPs) have demonstrated roles in immune modulation. In some cases, these enzymes are produced by parasites to influence host immune responses such that parasite infection is facilitated. One of the best examples of parasite-mediated immune modulation is the matrix metalloprotease (MMP) leishmanolysin (Gp63), which is produced by species of the genus Leishmania to evade killing by host macrophages. Leishmanolysin-like proteins appear to be quite common in many invertebrates, however our understanding of the functions of these non-leishmania enzymes is limited. Numerous proteomic and transcriptomic screens of schistosomes, at all life cycle stages of the parasite, have identified leishmanolysin-like MPs as being present in abundance; with the highest levels being found during the intramolluscan larval stages and being produced by cercaria. This study aims to functionally characterize a Schistosoma mansoni variant of leishmanolysin that most resembles the enzyme produced by Leishmania, termed SmLeish. We demonstrate that SmLeish is an important component of S. mansoni excretory/secretory (ES) products and is produced by the sporocyst during infection. The presence of SmLeish interferes with the migration of Biomphalaria glabrata haemocytes, and causes them to present a phenotype that is less capable of sporocyst encapsulation. Knockdown of SmLeish in S. mansoni miracidia prior to exposure to susceptible B. glabrata reduces miracidia penetration success, causes a delay in reaching patent infection, and lowers cercaria output from infected snails.

Parasitic flatworms, or digenetic trematodes, cause a wide range of diseases of both medical and agricultural importance. Nearly all species of digenea require specific species of snail for their larval development and transmission. The factors underpinning snail host specificity and how they dictate infection establishment and maintenance are interesting areas of research, both from the perspective of evolutionary immunology and potential application in the design of tools that aim to prevent trematode transmission. Currently, our understanding of snail-trematode associations is one-sided, being predominantly derived from studies that have focused on the snail immune response, with almost nothing known about how the parasite facilitates infection. Metalloproteases, such as leishmanolysin, are proteolytic enzymes; some of which are produced by parasites to influence host immune responses and facilitate parasite success upon encountering the host defense response. Here, we have functionally characterized a leishmanolysin-like metalloprotease (SmLeish) from Schistosoma mansoni, a causative agent of human schistosomiasis, which afflicts over 260 million people globally. We demonstrate that SmLeish is associated with developing sporocysts and is also located in S. mansoni excretory/secretory products and interferes with snail haemocyte morphology and migration. Knockdown of SmLeish in S. mansoni miracidia prior to exposure to Biomphalaria glabrata snails reduces miracidia penetration success, delays attainment of patent infections, and lowers cercaria output from infected snails.

A role for the metalloprotease invadolysin in insulin signaling and adipogenesis

Invadolysin is a novel metalloprotease conserved amongst metazoans that is essential for life in Drosophila. We previously showed that invadolysin was essential for the cell cycle and cell migration, linking to metabolism through a role in lipid storage and interaction with mitochondrial proteins. In this study we demonstrate that invadolysin mutants exhibit increased autophagy and decreased glycogen storage - suggestive of a role for invadolysin in insulin signaling in Drosophila. Consistent with this, effectors of insulin signaling were decreased in invadolysin mutants. In addition, we discovered that invadolysin was deposited on newly synthesized lipid droplets in a PKC-dependent manner. We examined two in vitro models of adipogenesis for the expression and localization of invadolysin. The level of invadolysin increased during both murine 3T3-L1 and human Simpson-Golabi-Behmel syndrome (SGBS), adipogenesis. Invadolysin displayed a dynamic localization to lipid droplets over the course of adipogenesis, which may be due to the differential expression of distinct invadolysin variants. Pharmacological inhibition of adipogenesis abrogated the increase in invadolysin. In summary, our results on in vivo and in vitro systems highlight an important role for invadolysin in insulin signaling and adipogenesis.

Next Generation Sequencing Identifies Five Major Classes of Potentially Therapeutic Enzymes Secreted by Lucilia sericata Medical Maggots

Lucilia sericata larvae are used as an alternative treatment for recalcitrant and chronic wounds. Their excretions/secretions contain molecules that facilitate tissue debridement, disinfect, or accelerate wound healing and have therefore been recognized as a potential source of novel therapeutic compounds. Among the substances present in excretions/secretions various peptidase activities promoting the wound healing processes have been detected but the peptidases responsible for these activities remain mostly unidentified. To explore these enzymes we applied next generation sequencing to analyze the transcriptomes of different maggot tissues (salivary glands, gut, and crop) associated with the production of excretions/secretions and/or with digestion as well as the rest of the larval body. As a result we obtained more than 123.8 million paired-end reads, which were assembled de novo using Trinity and Oases assemblers, yielding 41,421 contigs with an N50 contig length of 2.22 kb and a total length of 67.79 Mb. BLASTp analysis against the MEROPS database identified 1729 contigs in 577 clusters encoding five peptidase classes (serine, cysteine, aspartic, threonine, and metallopeptidases), which were assigned to 26 clans, 48 families, and 185 peptidase species. The individual enzymes were differentially expressed among maggot tissues and included peptidase activities related to the therapeutic effects of maggot excretions/secretions.

As the fat flies: The dynamic lipid droplets of Drosophila embryos

Research into lipid droplets is rapidly expanding, and new cellular and organismal roles for these lipid-storage organelles are continually being discovered. The early Drosophila embryo is particularly well suited for addressing certain questions in lipid-droplet biology and combines technical advantages with unique biological phenomena. This review summarizes key features of this experimental system and the techniques available to study it, in order to make it accessible to researchers outside this field. It then describes the two topics most heavily studied in this system, lipid-droplet motility and protein sequestration on droplets, discusses what is known about the molecular players involved, points to open questions, and compares the results from Drosophila embryo studies to what it is known about lipid droplets in other systems.

Invadolysin acts genetically via the SAGA complex to modulate chromosome structure

Identification of components essential to chromosome structure and behaviour remains a vibrant area of study. We have previously shown that invadolysin is essential in Drosophila, with roles in cell division and cell migration. Mitotic chromosomes are hypercondensed in length, but display an aberrant fuzzy appearance. We additionally demonstrated that in human cells, invadolysin is localized on the surface of lipid droplets, organelles that store not only triglycerides and sterols but also free histones H2A, H2Av and H2B. Is there a link between the storage of histones in lipid droplets and the aberrantly structured chromosomes of invadolysin mutants? We have identified a genetic interaction between invadolysin and nonstop, the de-ubiquitinating protease component of the SAGA (Spt-Ada-Gcn5-acetyltransferase) chromatin-remodelling complex. invadolysin and nonstop mutants exhibit phenotypic similarities in terms of chromosome structure in both diploid and polyploid cells. Furthermore, IX-14¹/not¹ transheterozygous animals accumulate mono-ubiquitinated histone H2B (ubH2B) and histone H3 tri-methylated at lysine 4 (H3K4me3). Whole mount immunostaining of IX-14¹/not¹ transheterozygous salivary glands revealed that ubH2B accumulates surprisingly in the cytoplasm, rather than the nucleus. Over-expression of the Bre1 ubiquitin ligase phenocopies the effects of mutating either the invadolysin or nonstop genes. Intriguingly, nonstop and mutants of other SAGA subunits (gcn5, ada2b and sgf11) all suppress an invadolysin-induced rough eye phenotype. We conclude that the abnormal chromosome phenotype of invadolysin mutants is likely the result of disrupting the histone modification cycle, as accumulation of ubH2B and H3K4me3 is observed. We further suggest that the mislocalization of ubH2B to the cytoplasm has additional consequences on downstream components essential for chromosome behaviour. We therefore propose that invadolysin plays a crucial role in chromosome organization via its interaction with the SAGA complex.

Architecture and function of metallopeptidase catalytic domains

The cleavage of peptide bonds by metallopeptidases (MPs) is essential for life. These ubiquitous enzymes participate in all major physiological processes, and so their deregulation leads to diseases ranging from cancer and metastasis, inflammation, and microbial infection to neurological insults and cardiovascular disorders. MPs cleave their substrates without a covalent intermediate in a single-step reaction involving a solvent molecule, a general base/acid, and a mono- or dinuclear catalytic metal site. Most monometallic MPs comprise a short metal-binding motif (HEXXH), which includes two metal-binding histidines and a general base/acid glutamate, and they are grouped into the zincin tribe of MPs. The latter divides mainly into the gluzincin and metzincin clans. Metzincins consist of globular ∼ 130-270-residue catalytic domains, which are usually preceded by N-terminal pro-segments, typically required for folding and latency maintenance. The catalytic domains are often followed by C-terminal domains for substrate recognition and other protein-protein interactions, anchoring to membranes, oligomerization, and compartmentalization. Metzincin catalytic domains consist of a structurally conserved N-terminal subdomain spanning a five-stranded β-sheet, a backing helix, and an active-site helix. The latter contains most of the metal-binding motif, which is here characteristically extended to HEXXHXXGXX(H,D). Downstream C-terminal subdomains are generally shorter, differ more among metzincins, and mainly share a conserved loop--the Met-turn--and a C-terminal helix. The accumulated structural data from more than 300 deposited structures of the 12 currently characterized metzincin families reviewed here provide detailed knowledge of the molecular features of their catalytic domains, help in our understanding of their working mechanisms, and form the basis for the design of novel drugs.

Invadolysin, a conserved lipid-droplet-associated metalloproteinase, is required for mitochondrial function in Drosophila

Mitochondria are the main producers of ATP, the principal energy source of the cell, and reactive oxygen species (ROS), important signaling molecules. Mitochondrial morphogenesis and function depend on a hierarchical network of mechanisms in which proteases appear to be center stage. The invadolysin gene encodes an essential conserved metalloproteinase of the M8 family that is necessary for mitosis and cell migration during Drosophila development. We previously demonstrated that invadolysin is found associated with lipid droplets in cells. Here, we present data demonstrating that invadolysin interacts physically with three mitochondrial ATP synthase subunits. Our studies have focused on the genetic phenotypes of invadolysin and bellwether, the Drosophila homolog of ATP synthase α, mutants. The invadolysin mutation presents defects in mitochondrial physiology similar to those observed in bellwether mutants. The invadolysin and bellwether mutants have parallel phenotypes that affect lipid storage and mitochondrial electron transport chain activity, which result in a reduction in ATP production and an accumulation of ROS. As a consequence, invadolysin mutant larvae show lower energetic status and higher oxidative stress. Our data demonstrate an essential role for invadolysin in mitochondrial function that is crucial for normal development and survival.

Perturbation of invadolysin disrupts cell migration in zebrafish (Danio rerio)

Invadolysin is an essential, conserved metalloprotease which links cell division with cell migration and is intriguingly associated with lipid droplets. In this work we examine the expression pattern, protein localisation and gross anatomical consequences of depleting invadolysin in the teleost Danio rerio. We observe that invadolysin plays a significant role in cell migration during development. When invadolysin is depleted by targeted morpholino injection, the appropriate deposition of neuromast clusters and distribution of melanophores are both disrupted. We also observe that blood vessels generated via angiogenesis are affected in invadolysin morphant fish while those formed by vasculogenesis appear normal, demonstrating an unanticipated role for invadolysin in vessel formation. Our results thus highlight a common feature shared by, and a requirement for invadolysin in, these distinct morphological events dependent on cell migration.

Comparative analysis of SV40 17kT and LT function in vivo demonstrates that LT's C-terminus re-programs hepatic gene expression and is necessary for tumorigenesis in the liver

Transformation by Simian Virus 40 (SV40) large T antigen (LT) is mediated in large part by its interaction with a variety of cellular proteins at distinct binding domains within LT. While the interaction of LT's N-terminus with the tumor suppressor Rb is absolutely required for LT-dependent transformation, the requirement for the interaction of LT's C-terminus with p53 is less clear and cell- and context-dependent. Here, we report a line of transgenic mice expressing a doxycycline-inducible liver-specific viral transcript that produces abundant 17kT, a naturally occurring SV40 early product that is co-linear with LT for the first 131 amino acids and that binds to Rb, but not p53. Comparative analysis of livers of transgenic mice expressing either 17kT or full length LT demonstrates that 17kT stimulates cell proliferation and induces hepatic hyperplasia but is incapable of inducing hepatic dysplasia or promoting hepatocarcinogenesis. Gene expression profiling demonstrates that 17kT and LT invoke a set of shared molecular signatures consistent with the action of LT's N-terminus on Rb-E2F-mediated control of hepatocyte transcription. However, 17kT also induces a unique set of genes, many of which are known transcriptional targets of p53, while LT actively suppresses them. LT also uniquely deregulates the expression of a subset of genes within the imprinted network and rapidly re-programs hepatocyte gene expression to a more fetal-like state. Finally, we provide evidence that the LT/p53 complex provides a gain-of-function for LT-dependent transformation in the liver, and confirm the absolute requirement for LT's C-terminus for liver tumor development by demonstrating that phosphatase and tensin homolog (PTEN)-deficiency readily cooperates with LT, but not 17kT, for tumorigenesis. These results confirm independent and inter-dependent functions for LT's N- and C-terminus and emphasize differences in the requirements for LT's C-terminus in cell-type dependent transformation.

Loss of the integrin-activating transmembrane protein Fam38A (Piezo1) promotes a switch to a reduced integrin-dependent mode of cell migration

Lung cancer is one of the most common fatal diseases in the developed world. The disease is rarely cured by currently available therapies, with an overall survival rate of ∼10%. Characterizing novel proteins that offer crucial insights into the processes of lung tumour invasion and metastasis may therefore provide much-needed prognostic markers, and influence therapeutic strategies. Aberrant function of the integrin family of heterodimeric cell surface receptors is a common theme in cancer - investigation into novel integrin activity regulators may offer crucial insights into the processes of tumour invasion and metastasis and may reveal insights into potential therapeutic targets. We previously described that depletion of the novel multi-transmembrane domain protein Fam38A, located at the endoplasmic reticulum (ER), inactivates endogenous beta1 integrin affinity, reducing cell adhesion. We now show that depletion of Fam38A, also now known as Piezo1, causes anchorage independence and a switch to a reduced integrin-dependent mode of cell migration/invasion, a novel phenotype for this integrin-regulating protein. Normal lung epithelial cells show increased rates of migration by 2D time-lapse microscopy and increased capacity to invade into matrigel, despite having decreased integrin affinity. We confirm greatly depleted Fam38A expression in small cell lung cancer (SCLC) lines where a form of reduced integrin-dependent migration, i.e. amoeboid migration, is a known phenotype. We propose that loss of Fam38A expression may cause increased cell migration and metastasis in lung tumours.

The dynamic roles of intracellular lipid droplets: from archaea to mammals

During the past decade, there has been a paradigm shift in our understanding of the roles of intracellular lipid droplets (LDs). New genetic, biochemical and imaging technologies have underpinned these advances, which are revealing much new information about these dynamic organelles. This review takes a comparative approach by examining recent work on LDs across the whole range of biological organisms from archaea and bacteria, through yeast and Drosophila to mammals, including humans. LDs probably evolved originally in microorganisms as temporary stores of excess dietary lipid that was surplus to the immediate requirements of membrane formation/turnover. LDs then acquired roles as long-term carbon stores that enabled organisms to survive episodic lack of nutrients. In multicellular organisms, LDs went on to acquire numerous additional roles including cell- and organism-level lipid homeostasis, protein sequestration, membrane trafficking and signalling. Many pathogens of plants and animals subvert their host LD metabolism as part of their infection process. Finally, malfunctions in LDs and associated proteins are implicated in several degenerative diseases of modern humans, among the most serious of which is the increasingly prevalent constellation of pathologies, such as obesity and insulin resistance, which is associated with metabolic syndrome.

Control of Entamoeba histolytica adherence involves metallosurface protease 1, an M8 family surface metalloprotease with homology to leishmanolysin

Invasive amebiasis due to Entamoeba histolytica infection is an important cause of morbidity in developing countries. The E. histolytica genome contains two homologues to the metalloprotease leishmanolysin gene, Entamoeba histolytica MSP-1 (EhMSP-1) and EhMSP-2, while the commensal ameba Entamoeba dispar has lost EhMSP-1. In this study, we sought to characterize E. histolytica metallosurface protease 1 (EhMSP-1). Using immunoprecipitation and a model substrate, we found that EhMSP-1 was a functional metalloprotease. Confocal microscopy and flow cytometry revealed that EhMSP-1 localized to the cell surface and revealed the existence of distinct, nonclonal trophozoite populations with high and low EhMSP-1 surface abundance that became synchronized following serum starvation. Phenotypic assays were performed after silencing EhMSP-1. Adherence of EhMSP-1-deficient trophozoites to tissue culture cell monolayers was more than five times greater than that of control amebas, but surface staining of several antigens, including the galactose adherence lectin, was unchanged. EhMSP-1 silencing similarly increased adherence to both viable and apoptotic Jurkat lymphocytes. Tissue culture cell monolayer destruction was reduced by EhMSP-1 silencing, although it was blocked almost completely by inhibiting cysteine proteases. Consistent with a primary defect in regulation of amebic adherence, EhMSP-1 silencing also resulted in reduced mobility on tissue culture cell monolayers and in increased phagocytosis. In conclusion, EhMSP-1 was shown to be a surface metalloprotease involved in regulation of amebic adherence, with additional effects on cell motility, cell monolayer destruction, and phagocytosis.

Mass spectrometric analysis identifies a cortactin-RCC2/TD60 interaction in mitotic cells

Cortactin is an F-actin binding protein that functions as a scaffold to regulate Arp2/3 mediated actin polymerization in lamellipodia and invadopodia formation as well as functioning in cell migration and endocytosis of many different cell types. In light of the fact that regulated actin polymerization is critical for many cellular processes we launched a search for novel cortactin interactions with cellular proteins that might indicate heretofore undescribed biological activities supported by cortactin. Using a modified stable isotope labeling in cell culture (SILAC) approach in HEK293 cells and Flag-tagged cortactin (F-cortactin) as bait, we identified a limited set of cortactin interactions including several proteins which have not previously been identified as cortactin associated proteins. Among these were serine/threonine-protein phosphatase 2A subunit beta (PP2A-beta) and RCC2/TD60, a Rac guanine nucleotide exchange factor (GEF) required for completion of mitosis and cytokinesis. The interaction between cortactin and RCC2/TD60 was verified in cell lysates immunoprecitated with anti-RCC2/TD60 antibody. Furthermore, cortactin was localized by immunofluorescence in the equatorial plane of dividing HeLa cells in the region where RCC2/TD60 has previously been localized thus providing support for a complex containing cortactin and RCC2/TD60 complex that may play a functional role in cells undergoing mitosis.

Glucocorticoid-mediated inhibition of angiogenic changes in human endothelial cells is not caused by reductions in cell proliferation or migration

Background

Glucocorticoid-mediated inhibition of angiogenesis is important in physiology, pathophysiology and therapy. However, the mechanisms through which glucocorticoids inhibit growth of new blood vessels have not been established. This study addresses the hypothesis that physiological levels of glucocorticoids inhibit angiogenesis by directly preventing tube formation by endothelial cells.

Methodology/Principal Findings

Cultured human umbilical vein (HUVEC) and aortic (HAoEC) endothelial cells were used to determine the influence of glucocorticoids on tube-like structure (TLS) formation, and on cellular proliferation (5-bromo-2′-deoxyuridine (BrdU) incorporation), viability (ATP production) and migration (Boyden chambers). Dexamethasone or cortisol (at physiological concentrations) inhibited both basal and prostaglandin F_2α (PGF_2α)-induced and vascular endothelial growth factor (VEGF) stimulated TLS formation in endothelial cells (ECs) cultured on Matrigel, effects which were blocked with the glucocorticoid receptor antagonist RU38486. Glucocorticoids had no effect on EC viability, migration or proliferation. Time-lapse imaging showed that cortisol blocked VEGF-stimulated cytoskeletal reorganisation and initialisation of tube formation. Real time PCR suggested that increased expression of thrombospodin-1 contributed to glucocorticoid-mediated inhibition of TLS formation.

Conclusions/Significance

We conclude that glucocorticoids interact directly with glucocorticoid receptors on vascular ECs to inhibit TLS formation. This action, which was conserved in ECs from two distinct vascular territories, was due to alterations in cell morphology rather than inhibition of EC viability, migration or proliferation and may be mediated in part by induction of thrombospodin-1. These findings provide important insights into the anti-angiogenic action of endogenous glucocorticoids in health and disease.

Integrin activation by Fam38A uses a novel mechanism of R-Ras targeting to the endoplasmic reticulum

The integrin family of heterodimeric cell-surface receptors are fundamental in cell-cell and cell-matrix adhesion. Changes to either integrin-ligand affinity or integrin gene expression are central to a variety of disease processes, including inflammation, cardiovascular disease and cancer. In screening for novel activators of integrin-ligand affinity we identified the previously uncharacterised multi-transmembrane domain protein Fam38A, located at the endoplasmic reticulum (ER). siRNA knockdown of Fam38A in epithelial cells inactivates endogenous beta1 integrin, reducing cell adhesion. Fam38A mediates integrin activation by recruiting the small GTPase R-Ras to the ER, which activates the calcium-activated protease calpain by increasing Ca(2+) release from cytoplasmic stores. Fam38A-induced integrin activation is blocked by inhibition of either R-Ras or calpain activity, or by siRNA knockdown of talin, a well-described calpain substrate. This highlights a novel mechanism for integrin activation by Fam38A, utilising calpain and R-Ras signalling from the ER. These data represent the first description of a novel spatial regulator of R-Ras, of an alternative integrin activation-suppression pathway based on direct relocalisation of R-Ras to the ER, and of a mechanism linking R-Ras and calpain signalling from the ER with modulation of integrin-ligand affinity.

Metalloproteases and the degradome

Metalloproteases comprise a heterogeneous group of proteolytic enzymes whose main characteristic is the utilization of a metal ion to polarize a water molecule and perform hydrolytic reactions. These enzymes represent the most densely populated catalytic class of proteases in many organisms and play essential roles in multiple biological processes. In this chapter, we will first present a general description of the complexity of metalloproteases in the context of the degradome, which is defined as the complete set of protease genes encoded by the genome of a certain organism. We will also discuss the functional relevance of these enzymes in a large variety of biological and pathological conditions. Finally, we will analyze in more detail three families of metalloproteases: ADAMs (a disintegrin and metalloproteinase), ADAMTSs (ADAMs with thrombospondin domains), and MMPs (matrix metalloproteinases) which have a growing relevance in a number of human pathologies including cancer, arthritis, neurodegenerative disorders, and cardiovascular diseases.

The conserved metalloprotease invadolysin localizes to the surface of lipid droplets

Invadolysin is a metalloprotease conserved in many different organisms, previously shown to be essential in Drosophila with roles in cell division and cell migration. The gene seems to be ubiquitously expressed and four distinct splice variants have been identified in human cells but not in most other species examined. Immunofluorescent detection of human invadolysin in cultured cells reveals the protein to be associated with the surface of lipid droplets. By means of subcellular fractionation, we have independently confirmed the association of invadolysin with lipid droplets. We thus identify invadolysin as the first metalloprotease located on these dynamic organelles. In addition, analysis of larval fat-body morphological appearance and triglyceride levels in the Drosophila invadolysin mutant suggests that invadolysin plays a role in lipid storage or metabolism.

Catalytic domain architecture of metzincin metalloproteases

Metalloproteases cleave proteins and peptides, and deregulation of their function leads to pathology. An understanding of their structure and mechanisms of action is necessary to the development of strategies for their regulation. Among metallopeptidases are the metzincins, which are mostly multidomain proteins with approximately 130-260-residue globular catalytic domains showing a common core architecture characterized by a long zinc-binding consensus motif, HEXXHXXGXX(H/D), and a methionine-containing Met-turn. Metzincins participate in unspecific protein degradation such as digestion of intake proteins and tissue development, maintenance, and remodeling, but they are also involved in highly specific cleavage events to activate or inactivate themselves or other (pro)enzymes and bioactive peptides. Metzincins are subdivided into families, and seven such families have been analyzed at the structural level: the astacins, ADAMs/adamalysins/reprolysins, serralysins, matrix metalloproteinases, snapalysins, leishmanolysins, and pappalysins. These families are reviewed from a structural point of view.

Meprins, membrane-bound and secreted astacin metalloproteinases

The astacins are a subfamily of the metzincin superfamily of metalloproteinases. The first to be characterized was the crayfish enzyme astacin. To date more than 200 members of this family have been identified in species ranging from bacteria to humans. Astacins are involved in developmental morphogenesis, matrix assembly, tissue differentiation and digestion. Family members include the procollagen C-proteinase (BMP1, bone morphogenetic protein 1), tolloid and mammalian tolloid-like, HMP (Hydra vulgaris metalloproteinase), sea urchin BP10 (blastula protein) and SPAN (Strongylocentrotus purpuratus astacin), the 'hatching' subfamily comprising alveolin, ovastacin, LCE, HCE ('low' and 'high' choriolytic enzymes), nephrosin (from carp head kidney), UVS.2 from frog, and the meprins. In the human and mouse genomes, there are six astacin family genes (two meprins, three BMP1/tolloid-like, one ovastacin), but in Caenorhabditis elegans there are 40. Meprins are the only astacin proteinases that function on the membrane and extracellularly by virtue of the fact that they can be membrane-bound or secreted. They are unique in their domain structure and covalent subunit dimerization, oligomerization propensities, and expression patterns. They are normally highly regulated at the transcriptional and post-translational levels, localize to specific membranes or extracellular spaces, and can hydrolyse biologically active peptides, cytokines, extracellular matrix (ECM) proteins and cell-surface proteins. The in vivo substrates of meprins are unknown, but the abundant expression of these proteinases in the epithelial cells of the intestine, kidney and skin provide clues to their functions.

Podosomes and Invadopodia: Related structures with Common Protein Components that May Promote Breast Cancer Cellular Invasion

A rate-limiting step in breast cancer progression is acquisition of the invasive phenotype, which can precede metastasis. Expression of cell-surface proteases at the leading edge of a migrating cell provides cells with a mechanism to cross tissue barriers. A newly appreciated mechanism that may be relevant for breast cancer cell invasion is the formation of invadopodia, well-defined structures that project from the ventral membrane and promote degradation of the extracellular matrix, allowing the cell to cross a tissue barrier. Recently, there has been some controversy and discussion as to whether invadopodia, which are associated with carcinoma cells, are related to a similar structure called podosomes, which are associated with normal cells. Invadopodia and podosomes share many common characteristics, including a similar size, shape, subcellular localization and an ability to promote invasion. These two structures also share many common protein components, which we outline herein. It has been speculated that podosomes may be precursors to invadopodia and by extension both structures may be relevant to cancer cell invasion. Here, we compare and contrast the protein components of invadopodia and podosomes and discuss a potential role for these proteins and the evidence that supports a role for invadopodia and podosomes in breast cancer invasion.

Subtypes of glial cells in the Drosophila embryonic ventral nerve cord as related to lineage and gene expression

In the Drosophila embryonic CNS several subtypes of glial cells develop, which arrange themselves at characteristic positions and presumably fulfil specific functions. The mechanisms leading to the specification and differentiation of glial subtypes are largely unknown. By DiI labelling in glia-specific Gal4 lines we have clarified the lineages of the lateral glia in the embryonic ventral nerve cord and linked each glial cell to a specific stem cell. For the lineage of the longitudinal glioblast we show that it consists of 9 cells, which acquire at least four different identities. A large collection of molecular markers (many of them representing transcription factors and potential Gcm target genes) reveals that individual glial cells express specific combinations of markers. However, cluster analysis uncovers similar combinatorial codes for cells within, and significant differences between the categories of surface-associated, cortex-associated, and longitudinal glia. Glial cells derived from the same stem cell may be homogeneous (though not identical; stem cells NB1-1, NB5-6, NB6-4, LGB) or heterogeneous (NB7-4, NB1-3) with regard to gene expression. In addition to providing a powerful tool to analyse the fate of individual glial cells in different genetic backgrounds, each of these marker genes represents a candidate factor involved in glial specification or differentiation. We demonstrate this by the analysis of a castor loss of function mutation, which affects the number and migration of specific glial cells.

The matrix corroded: podosomes and invadopodia in extracellular matrix degradation

Podosomes and invadopodia are unique actin-rich adhesions that establish close contact to the substratum but can also degrade components of the extracellular matrix. Accordingly, matrix degradation localized at podosomes or invadopodia is thought to contribute to cellular invasiveness in physiological and pathological situations. Cell types that form podosomes include monocytic, endothelial and smooth muscle cells, whereas invadopodia have been mostly observed in carcinoma cells. This review highlights important new developments in the field, discusses the common and divergent features of podosomes and invadopodia and summarizes current knowledge about matrix-degrading proteinases at these structures.

In vivo migration: a germ cell perspective

The basic concepts of the molecular machinery that mediates cell migration have been gleaned from cell culture systems. However, the three-dimensional environment within an organism presents migrating cells with a much greater challenge. They must move between and among other cells while interpreting multiple attractive and repulsive cues to choose their proper path. They must coordinate their cell adhesion with their surroundings and know when to start and stop moving. New insights into the control of these remaining mysteries have emerged from genetic dissection and live imaging of germ cell migration in Drosophila, zebrafish, and mouse embryos. In this review, we first describe germ cell migration in cellular and mechanistic detail in these different model systems. We then compare these systems to highlight the emerging principles. Finally, we contrast the migration of germ cells with that of immune and cancer cells to outline the conserved and different mechanisms.

A metalloproteinase gene from the pathogenic piscine hemoflagellate, Cryptobia salmositica

We report the identification of a Cryptobia genomic DNA gene predicted to encode a hydrophobic protein containing a zinc metalloproteinase motif, HEXXH, and hence named it a major surface proteinase 1-like (MSP-1). The MSP-1 gene was identified using universal genome walking. Southern blot analysis revealed it to be a multicopy gene. Fragments of DNA encoding a segment homologous to the HEXXH motif of MSP-1 are widely found in bacteria, yeast, parasitic protozoans, plants, and animals including humans. These results suggest that the MSP-1 may have highly conserved functions, such as in intracellular proteolysis.

Vinegar flies turn to porto for cell division cycle meeting

The Third International Workshop on Drosophila Cell Division Cycle brought together researchers focusing on DNA replication, mitosis, meiosis, cell cycle regulation, checkpoints, asymmetric division, cell and tissue growth, and tumorgenesis. This review describes new findings presented at the meeting that particularly highlight the advantages of the Drosophila systems.

Insights into the role of gp63-like proteins in lower trypanosomatids

Any actual understanding of trypanosomatids in general requires a comprehensive analysis of the less-specialized species as thorough as our knowledge of the more specialized Leishmania and Trypanosoma. In this context, we have shown by antibody cross-reactivity that purified extracellular metallopeptidases from Phytomonas françai, Crithidia deanei (cured strain) and Crithidia guilhermei share common epitopes with the leishmanial gp63. Flow cytometry and fluorescence microscopy analyses indicated the presence of gp63-like molecules on the cell surface of these lower trypanosomatids. Binding assays with explanted guts of Aedes aegypti incubated with purified gp63 and the pretreatment of trypanosomatids with anti-gp63 antibodies indicated that the gp63-like molecules are involved in the adhesive process of these trypanosomatids to the A. aegypti gut wall. In addition, our results indicate for the first time that the gp63-like molecule binds to a polypeptide of 50 kDa on the A. aegypti gut epithelium extract.

A signalling cascade involving PKC, Src and Cdc42 regulates podosome assembly in cultured endothelial cells in response to phorbol ester

The involvement of Src, Cdc42, RhoA and PKC in the regulation of podosome assembly has been identified in various cell models. In endothelial cells, the ectopic expression of constitutively active mutants of Src or Cdc42, but not RhoA, induced the formation of podosomes. Short-term exposure to phorbol-12-myristate-13-acetate (PMA) induced the appearance of podosomes and rosettes after initial disruption of stress fibres. Molecular analysis of PMA-induced podosomes and rosettes revealed that their composition was identical to that of podosomes described in other models. Pharmacological inhibition and siRNA knock-down experiments revealed that both PKCalpha and PKCdelta isotypes were necessary for podosome assembly. However, only constitutively active PKCalpha could mimic PMA in podosome formation. Src, Cdc42 and RhoA were required downstream of PKCs in this process. Src could be positioned between PKC and Cdc42 in a linear cascade leading to podosome assembly. Using in vitro matrix degradation assays, we demonstrated that PMA-induced podosomes are endowed with proteolytic activities involving MT1-MMP-mediated activation of MMP2. Endothelial podosomes may be involved in subendothelial matrix degradation during endothelium remodelling in pathophysiological processes.

Cell migration in tumors

Invasion of cancer cells into surrounding tissue and the vasculature is an initial step in tumor metastasis. This requires chemotactic migration of cancer cells, steered by protrusive activity of the cell membrane and its attachment to the extracellular matrix. Recent advances in intravital imaging and the development of an in vivo invasion assay have provided new insights into how cancer cell migration is regulated by elements of the local microenvironment, including the extracellular matrix architecture and other cell types found in primary tumors. These results, combined with new findings from in vitro studies, have led to new insights into the molecular mechanisms of cell protrusive activity and chemotactic migration during invasion and metastasis.

Diverse mitotic and interphase functions of condensins in Drosophila

The condensin complex has been implicated in the higher-order organization of mitotic chromosomes in a host of model eukaryotes from yeasts to flies and vertebrates. Although chromosomes paradoxically appear to condense in condensin mutants, chromatids are not properly resolved, resulting in chromosome segregation defects during anaphase. We have examined the role of different condensin complex components in interphase chromatin function by examining the effects of various condensin mutations on position-effect variegation in Drosophila melanogaster. Surprisingly, most mutations affecting condensin proteins were often found to result in strong enhancement of variegation in contrast to what might be expected for proteins believed to compact the genome. This suggests either that the role of condensin proteins in interphase differs from their expected role in mitosis or that the way we envision condensin's activity needs to be modified to accommodate alternative possibilities.

DrosophilaCAP-D2 is required for condensin complex stability and resolution of sister chromatids

The precise mechanism of chromosome condensation and decondensation remains a mystery, despite progress over the last 20 years aimed at identifying components essential to the mitotic compaction of the genome. In this study, we analyse the localization and role of the CAP-D2 non-SMC condensin subunit and its effect on the stability of the condensin complex. We demonstrate that a condensin complex exists in Drosophila embryos, containing CAP-D2, the anticipated SMC2 and SMC4 proteins, the CAP-H/Barren and CAP-G (non-SMC) subunits. We show that CAP-D2 is a nuclear protein throughout interphase, increasing in level during S phase, present on chromosome axes in mitosis, and still present on chromosomes as they start to decondense late in mitosis. We analysed the consequences of CAP-D2 loss after dsRNA-mediated interference, and discovered that the protein is essential for chromosome arm and centromere resolution. The loss of CAP-D2 after RNAi has additional downstream consequences on the stability of CAP-H, the localization of DNA topoisomerase II and other condensin subunits, and chromosome segregation. Finally, we discovered that even after interfering with two components important for chromosome architecture (DNA topoisomerase II and condensin), chromosomes were still able to compact, paving the way for the identification of further components or activities required for this essential process.