Heparan sulfate proteoglycans: structure, protein interactions and cell signaling

Heparan sulfate proteoglycans are ubiquitously found at the cell surface and extracellular matrix in all the animal species. This review will focus on the structural characteristics of the heparan sulfate proteoglycans related to protein interactions leading to cell signaling. The heparan sulfate chains due to their vast structural diversity are able to bind and interact with a wide variety of proteins, such as growth factors, chemokines, morphogens, extracellular matrix components, enzymes, among others. There is a specificity directing the interactions of heparan sulfates and target proteins, regarding both the fine structure of the polysaccharide chain as well precise protein motifs. Heparan sulfates play a role in cellular signaling either as receptor or co-receptor for different ligands, and the activation of downstream pathways is related to phosphorylation of different cytosolic proteins either directly or involving cytoskeleton interactions leading to gene regulation. The role of the heparan sulfate proteoglycans in cellular signaling and endocytic uptake pathways is also discussed.Proteoglicanos de heparam sulfato são encontrados tanto superfície celular quanto na matriz extracelular em todas as espécies animais. Esta revisão tem enfoque nas características estruturais dos proteoglicanos de heparam sulfato e nas interações destes proteoglicanos com proteínas que levam à sinalização celular. As cadeias de heparam sulfato, devido a sua variedade estrutural, são capazes de se ligar e interagir com ampla gama de proteínas, como fatores de crescimento, quimiocinas, morfógenos, componentes da matriz extracelular, enzimas, entreoutros. Existe uma especificidade estrutural que direciona as interações dos heparam sulfatos e proteínas alvo. Esta especificidade está relacionada com a estrutura da cadeia do polissacarídeo e os motivos conservados da cadeia polipeptídica das proteínas envolvidas nesta interação. Os heparam sulfatos possuem papel na sinalização celular como receptores ou coreceptores para diferentes ligantes. Esta ligação dispara vias de sinalização celular levam à fosforilação de diversas proteínas citosólicas ou com ou sem interações diretas com o citoesqueleto, culminando na regulação gênica. O papel dos proteoglicanos de heparam sulfato na sinalização celular e vias de captação endocítica também são discutidas nesta revisão.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Universidade Federal de São Paulo (UNIFESP) Departamento de BioquímicaUniversidade Federal de São Paulo (UNIFESP) Departamento de OftalmologiaUNIFESP, Depto. de BioquímicaUNIFESP, Depto. de OftalmologiaSciEL

Extracting Sand Microarthropods - a Carbon-tetrachloride Flotation Method

A carbon tetrachloride flotation method is tested in the laboratory and in the field. Its efficiency approaches 100% in the laboratory and densities observed in the field exceed all densities previously published. The method is simple to perform but limited to low organic soils

Diversity of soil oribatid mites (Acari : Oribatida) from High Katanga (Democratic Republic of Congo): a multiscale and multifactor approach

Although the soil is a major reservoir of biodiversity, our knowledge of its mesofauna remains scanty, especially in the tropics. The diversity of oribatids (149 adult oribatid mite species) is analyzed for the first time in an African soil and studied in three ecosystems of a regressive sere: forest, woodland and savanna. Savanna is the richest ecosystem overall, with 105 collected species, whereas the mean number of species per releve (alpha diversity) is highest in forest. In barren soils, the number of species observed along the sere drops regularly from the typical forest to the savanna. However, this pattern is complicated by other factors acting at different scales. The increase of oribatid richness parallels that of habitat complexity, from barren soil to termitaria colonized by grasses and trees. On a finer scale, soil properties also influence species richness, either indirectly through density (water content) or directly (total nitrogen, C/N ratio, organic matter), but their importance varies in relation to seasons. Most exclusive species (nearly 90%) are housed in the two extreme types of vegetation, forest and savanna. On a finer scale, two habitats, the typical forest and the termitaria in the savanna, are remarkable by the number of exclusive species and are worth protecting through effective conservation measures