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

Berry Flesh and Skin Ripening Features in Vitis vinifera as Assessed by Transcriptional Profiling

Background Ripening of fleshy fruit is a complex developmental process involving the differentiation of tissues with separate functions. During grapevine berry ripening important processes contributing to table and wine grape quality take place, some of them flesh- or skin-specific. In this study, transcriptional profiles throughout flesh and skin ripening were followed during two different seasons in a table grape cultivar ‘Muscat Hamburg’ to determine tissue-specific as well as common developmental programs. Methodology/Principal Findings Using an updated GrapeGen Affymetrix GeneChip® annotation based on grapevine 12×v1 gene predictions, 2188 differentially accumulated transcripts between flesh and skin and 2839 transcripts differentially accumulated throughout ripening in the same manner in both tissues were identified. Transcriptional profiles were dominated by changes at the beginning of veraison which affect both pericarp tissues, although frequently delayed or with lower intensity in the skin than in the flesh. Functional enrichment analysis identified the decay on biosynthetic processes, photosynthesis and transport as a major part of the program delayed in the skin. In addition, a higher number of functional categories, including several related to macromolecule transport and phenylpropanoid and lipid biosynthesis, were over-represented in transcripts accumulated to higher levels in the skin. Functional enrichment also indicated auxin, gibberellins and bHLH transcription factors to take part in the regulation of pre-veraison processes in the pericarp, whereas WRKY and C2H2 family transcription factors seems to more specifically participate in the regulation of skin and flesh ripening, respectively. Conclusions/Significance A transcriptomic analysis indicates that a large part of the ripening program is shared by both pericarp tissues despite some components are delayed in the skin. In addition, important tissue differences are present from early stages prior to the ripening onset including tissue-specific regulators. Altogether, these findings provide key elements to understand berry ripening and its differential regulation in flesh and skin.This study was financially supported by GrapeGen Project funded by Genoma España within a collaborative agreement with Genome Canada. The authors also thank The Ministerio de Ciencia e Innovacion for project BIO2008-03892 and a bilateral collaborative grant with Argentina (AR2009-0021). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewe

Mac-1 (CD11b/CD18) and CD45 mediate the adhesion of hematopoietic progenitor cells to stromal cell elements via recognition of stromal heparan sulfate

Hematopoiesis is regulated by two sets of signals, those generated by cytokines and those generated when precursor cells interact with bone marrow (BM) stroma. The intimate contact between precursors and stroma appears to be mediated by multiple, different receptor-ligand binding events. To identify receptor-ligand pairs mediating the adhesion of hematopoietic precursor cells to stroma, an in vitro model of hematopoiesis was used. This involved coculturing the BM-derived, interleukin-3 (IL-3)-dependent, multipotential cells, FCDP-mix A4 (A4) with a stromal equivalent embryonic mesenchymal cell line, Swiss 3T3 (3T3). In coculture, A4 cells survive, proliferate, and differentiate in the absence of exogenous IL-3, providing they are attached to the 3T3 cell surface. By using detergent lysates of surface-biotinylated A4 cells, A4 cell molecules that bind to the stroma could be detected by either fluorescein isothiocyanate (FITC)-streptavidin or FITC-antibody staining and flow cytometry. Using this approach the beta 2 integrin, Mac-1, and CD45, a receptor-type tyrosine phosphatase, were identified as molecules on the A4 cell surface that bind 3T3 cells. Various glycosaminoglycans (GAGs), particularly heparin and heparan sulfate, blocked binding of A4 cell surface molecules to the 3T3 cells. The binding of CD45 and Mac-1 to the 3T3 cells was similarly blocked by these GAGs. Removal of heparin-binding molecules from A4 cell lysates diminished binding to the 3T3 cells and digestion of the 3T3 cell surface with heparinase abolished the binding of CD45 and Mac-1. The data suggest that heparan sulfate on the 3T3 cell surface is a ligand for both CD45 and Mac-1, but the two molecules recognize different heparan sulfate structural motifs.</jats:p

Mac-1 (CD11b/CD18) and CD45 mediate the adhesion of hematopoietic progenitor cells to stromal cell elements via recognition of stromal heparan sulfate

Abstract Hematopoiesis is regulated by two sets of signals, those generated by cytokines and those generated when precursor cells interact with bone marrow (BM) stroma. The intimate contact between precursors and stroma appears to be mediated by multiple, different receptor-ligand binding events. To identify receptor-ligand pairs mediating the adhesion of hematopoietic precursor cells to stroma, an in vitro model of hematopoiesis was used. This involved coculturing the BM-derived, interleukin-3 (IL-3)-dependent, multipotential cells, FCDP-mix A4 (A4) with a stromal equivalent embryonic mesenchymal cell line, Swiss 3T3 (3T3). In coculture, A4 cells survive, proliferate, and differentiate in the absence of exogenous IL-3, providing they are attached to the 3T3 cell surface. By using detergent lysates of surface-biotinylated A4 cells, A4 cell molecules that bind to the stroma could be detected by either fluorescein isothiocyanate (FITC)-streptavidin or FITC-antibody staining and flow cytometry. Using this approach the beta 2 integrin, Mac-1, and CD45, a receptor-type tyrosine phosphatase, were identified as molecules on the A4 cell surface that bind 3T3 cells. Various glycosaminoglycans (GAGs), particularly heparin and heparan sulfate, blocked binding of A4 cell surface molecules to the 3T3 cells. The binding of CD45 and Mac-1 to the 3T3 cells was similarly blocked by these GAGs. Removal of heparin-binding molecules from A4 cell lysates diminished binding to the 3T3 cells and digestion of the 3T3 cell surface with heparinase abolished the binding of CD45 and Mac-1. The data suggest that heparan sulfate on the 3T3 cell surface is a ligand for both CD45 and Mac-1, but the two molecules recognize different heparan sulfate structural motifs.</jats:p

Heparan sulfate inhibitors and their therapeutic implications in inflammatory illnesses

Introduction: Heparan sulfate (HS) is a polysaccharide that is ubiquitously expressed on the cell surface and in the extracellular matrix and interacts with a wide variety of proteins to mediate numerous biological and pathological functions, including inflammation. Areas covered: The structural diversity and the multiple biological roles of HS in inflammation are discussed. HS is involved in the recruitment and attachment of leukocytes to the inflamed epithelium, the activation of chemokines and the transmigration of leukocytes to the underlying target tissue. The endoglycosidase heparanase plays a key role in the above processes via the degradation of HS. HS mimetics that inhibit heparanase and block HS-binding proteins have been shown to inhibit inflammation in multiple animal models. Expert opinion: HS plays important roles in many stages of the inflammation process, in particular the regulation of leukocyte extravasation. Compounds that can inhibit HS-protein interactions thus have considerable potential as anti-inflammatory therapeutics capable of simultaneously interfering with multiple steps of the inflammation process. There are a number of such compounds in various stages of clinical development for cancer, which should also find applications in inflammatory illnesses