Ectomycorrhizal fungal succession in mixed temperate forests

Ectomycorrhizal (ECM) fungal communities of Douglas-fir (Pseudotsuga menziesii) and paper birch (Betula papyrifera) were studied along a chronosequence of forest development after stand-replacing disturbance. Previous studies of ECM succession did not use molecular techniques for fungal identification or lacked replication, and none examined different host species. Four age classes of mixed forests were sampled: 5-, 26-, 65-, and 100-yr-old, including wildfire-origin stands from all four classes and stands of clearcut origin from the youngest two classes. Morphotyping and DNA sequences were used to identify fungi on ECM root tips. ECM fungal diversities were lower in 5-yr-old than in older stands on Douglas-fir, but were similar among age classes on paper birch. Host-specific fungi dominated in 5-yr-old stands, but host generalists were dominant in the oldest two age classes. ECM fungal community compositions were similar in 65- and 100-yr-old stands but differed among all other pairs of age classes. Within the age range studied, site-level ECM fungal diversity reached a plateau by the 26-yr-old age class, while community composition stabilized by the 65-yr-old class. Simple categories such as 'early stage', 'multi stage', and 'late stage' were insufficient to describe fungal species' successional patterns. Rather, ECM fungal succession may be best described in the context of stand development.     

Does ectomycorrhizal fungal community structure vary along a Japanese black pine (Pinus thunbergii) to black locust (Robinia pseudoacacia) gradient?

In this study we examined the role of the nitrogen-fixing tree, Robinia pseudoacacia (black locust), in ectomycorrhizal (ECM) formation and ECM community of Pinus thunbergii (Japanese black pine) seedlings. Two 200 m(2) experimental plots were established at the border between a Japanese black pine- and a black locust-dominated area in a coastal forest. The ECM fungal community of pine seedlings was examined by PCR-RFLP and sequence analysis. We analyzed the relationship between ECM formation, ECM community, growth, and nutrient status of pine seedlings and environmental conditions using the Mantel test and structural equation model. Percentages of ECM root tips, the number of ECM fungal species and ECM diversity on pine seedlings decreased in the black locust-dominated area. Cenococcum geophilum and Russula spp. were dominant in the Japanese black pine-dominated area, whereas Tomentella spp. were dominant in the black locust-dominated area. Nitrogen (N) concentration in soils or pine seedlings strongly influenced the percentage of ECM root tips, the number of ECM fungal species and ECM fungal similarity. These results imply the long-term eutrophication caused by N-fixing trees can change ECM formation and ECM community structure.     

Cellular remodelling of individual collagen fibrils visualized by time-lapse AFM

The extracellular matrix in tissues such as bone, tendon and cornea contains ordered, parallel arrays of collagen type I fibrils. Cells embedded in these matrices frequently co-align with the collagen fibrils, suggesting that ordered fibrils provide structural or signalling cues for cell polarization. To study mechanisms of matrix-induced cell alignment, we used nanoscopically defined two-dimensional matrices assembled of highly aligned collagen type I fibrils. On these matrices, different cell lines expressing integrin alpha(2)beta(1) polarized strongly in the fibril direction. In contrast, alpha(2)beta(1)-deficient cells adhered but polarized less well, suggesting a role of integrin alpha(2)beta(1) in the alignment process. Time-lapse atomic force microscopy (AFM) demonstrated that during alignment cells deform the matrix by reorienting individual collagen fibrils. Cells deformed the collagen matrix asymmetrically, revealing an anisotropy in matrix rigidity. When matrix rigidity was rendered uniform by chemical cross-linking or when the matrix was formed from collagen fibrils of reduced tensile strength, cell polarization was prevented. This suggested that both the high tensile strength and pliability of collagen fibrils contribute to the anisotropic rigidity of the matrix, leading to directional cellular traction and cell polarization. During alignment, cellular protrusions contacted the collagen matrix from below and above. This complex entanglement of cellular protrusions and collagen fibrils may further promote cell alignment by maximizing cellular traction.     

DACS, novel matrix structure composed of chondroitin sulfate proteoglycan in the brain

Chondroitin sulfate proteoglycans (CSPGs) are major components of the extracellular matrix (ECM) in the brain. In the adult cerebral cortex, there are special CSPG-containing structures known as perineuronal nets (PNNs), which are highly condensed ECM structures. Here, we report a novel CSPG-containing structure distinct from PNNs in the adult mouse cerebral cortex. An anti-chondroitin sulfate antibody CS56 delineated a structure with a unique morphology like a dandelion clock. Accordingly, we named it DAndelion Clock-like Structure (DACS). Immunohistochemical evidence showed that DACSs surrounded a group of NeuN-positive/GABA-negative neurons. At ultrastructural level, CS56-immunoreactivities were localized in the cytoplasm and on the membrane of astrocytes. As the postnatal cerebral cortex matured, DACSs became visible around the end of the critical period. This is the first report demonstrating the presence of an ECM structure DACS composed of CSPGs around a group of cortical neurons in the adult cerebral cortex.     

Binding of host extracellular matrix proteins to Mycoplasma fermentans and its effect on adherence to, and invasion of HeLa cells

In the present study, we show that intact Mycoplasma fermentans cells have a wealth of adhesive interactions with components of the extracellular matrix. Mycoplasma fermentans intensively bind plasminogen, and to a lesser extent, fibronectin, heparin, and laminin. The binding of collagen type III, IV, or V was low. The binding of plasminogen, collagen type III, or collagen type V markedly enhanced the adherence of M. fermentans to HeLa cells, whereas the binding of fibronectin, heparin, laminin, or collagen IV induced only a small effect on mycoplasma adherence. Utilizing plasminogen-treated M. fermentans preparations, we detected microorganisms within host HeLa cells by the gentamicin protection assay or by confocal laser scanning microscopy of immunofluorescent preparations. However, no intracellular M. fermentans was detected when M. fermentans preparations treated with fibronectin, heparin, laminin, or collagen type III, IV, or V were utilized.     

Calorie restriction-induced changes in the secretome of human adipocytes,comparison with resveratrol-induced secretome effects

Obesity is characterized by dysfunctional white adipose tissue (WAT) that ultimately may lead to metabolic diseases. Calorie restriction (CR) reduces the risk for age and obesity-associated complications. The impact of CR on obesity has been examined with human intervention studies, which showed alterations in circulating adipokines. However, a direct effect of CR on the human adipocyte secretome remains elusive. Therefore, the effect of a 96 h low glucose CR on the secretion profile of in vitro cultured mature human SGBS adipocytes was investigated by using proteomics technology. Low-glucose CR decreased the adipocyte triglyceride contents and resulted in an altered secretion profile. Changes in the secretome indicated an improved inflammatory phenotype. In addition, several adipocyte-secreted proteins related to insulin resistance showed a reversed expression after low-glucose CR. Furthermore, 6 novel CR-regulated adipocyte-secreted proteins were identified. Since resveratrol (RSV) mimics CR we compared results from this study with data from our previous RSV study on the SGBS adipocyte secretome. The CR and RSV adipocyte secretomes partly differed from each other, although both treatment strategies lead to secretome changes indicating a less inflammatory phenotype. Furthermore, both treatments induced SIRT1 expression and resulted in a reversed expression of detrimental adipokines associated with metabolic complications.     

Disialoganglioside GD3-synthase over expression inhibits survival and angiogenesis of pancreatic cancer cells through cell cycle arrest at S-phase and disruption of integrin-β1-mediated anchorage

Gangliosides play important roles in the development, differentiation and proliferation of mammalian cells. They bind to other cell membrane components through their terminal sialic acids. Different gangliosides influence cellular functions based on the positions and linkages of sialic acids. Expression of gangliosides mainly depends on the status of sialic acid-modulatory enzymes, such as different types of sialyltransferases and sialidases. One such sialyltransferase, disialoganglioside GD3 synthase, is specifically responsible for the production of GD3. Pancreatic ductal adenocarcinoma, making up more than 90% of pancreatic cancers, is a fatal malignancy with poor prognosis. Despite higher sialylation status, the disialoganglioside GD3 level is very low in this cancer. However, the exact status and function of this disialoganglioside is still unknown. Here, we intended to study the intracellular mechanism of disialoganglioside GD3-induced apoptosis and its correlation with the adhesion and angiogenic pathways in pancreatic cancer. We demonstrated that disialoganglioside GD3 synthase-transfected cells showed enhanced apoptosis and it caused the arrest of these cells in the S-phase of the cell cycle. Integrins, a family of transmembrane proteins play important role in cell–cell recognition, invasion, adhesion and migration. disialoganglioside GD3 co-localised with integrin-β1 and thereby inhibited it's downstream signalling in transfected cells. Transfected cells exhibited inhibition of cell adhesion with extracellular matrix proteins. Enhanced GD3 expression down regulated angiogenesis-regulatory proteins and inhibited epidermal growth factor/vascular endothelial growth factor-driven angiogenic cell growth in these cells. Taken together, our study provides support for the GD3-induced cell cycle arrest, disruption of integrin-β1-mediated anchorage, inhibition of angiogenesis and thereby induced apoptosis in pancreatic cancer cells.     

Molecular functions of the iron-regulated metastasis suppressor,NDRG1, and its potential as a molecular target for cancer therapy

N-myc down-regulated gene 1 (NDRG1) is a known metastasis suppressor in multiple cancers, being also involved in embryogenesis and development, cell growth and differentiation, lipid biosynthesis and myelination, stress responses and immunity. In addition to its primary role as a metastasis suppressor, NDRG1 can also influence other stages of carcinogenesis, namely angiogenesis and primary tumour growth. NDRG1 is regulated by multiple effectors in normal and neoplastic cells, including N-myc, histone acetylation, hypoxia, cellular iron levels and intracellular calcium. Further, studies have found that NDRG1 is up-regulated in neoplastic cells after treatment with novel iron chelators, which are a promising therapy for effective cancer management. Although the pathways by which NDRG1 exerts its functions in cancers have been documented, the relationship between the molecular structure of this protein and its functions remains unclear. In fact, recent studies suggest that, in certain cancers, NDRG1 is post-translationally modified, possibly by the activity of endogenous trypsins, leading to a subsequent alteration in its metastasis suppressor activity. This review describes the role of this important metastasis suppressor and discusses interesting unresolved issues regarding this protein.     

Versican and the regulation of cell phenotype in disease

Background

Versican is an extracellular matrix (ECM) proteoglycan that is present in the pericellular environment of most tissues and increases in many different diseases. Versican interacts with cells to influence the ability of cells to proliferate, migrate, adhere and assemble an ECM.

Scope of review

The structure of the versican molecule is briefly reviewed and studies highlighting those factors that promote versican synthesis and degradation and their impact on cell phenotype in disease are discussed. Particular attention is given to vascular disease, but other diseases where versican is important are covered as well, most notably different forms of cancers. Attention is given to mechanisms(s) by which versican influences cell behaviors through either direct or indirect processes. Versican produced by either stromal cells or myeloid cells can have a major impact influencing immunity and inflammation. Finally, studies controlling versican accumulation that either delay or inhibit the progression of disease will be highlighted.

Major conclusions

Versican is one component of the ECM that can influence the ability of cells to proliferate, migrate, adhere, and remodel the ECM. Targeting versican as a way to control cell phenotype offers a novel approach in the treatment of disease.

Significance

ECM molecules such as versican contribute to the structural integrity of tissues and interact with cells through direct and indirect means to regulate, in part, cellular events that form the basis of disease. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.