High impact information on HSPG

• Recombinant agrin is a heparan sulfate proteoglycan (HSPG) of more than 400 kD with glycosaminoglycan side chains attached only to the NH2-terminal half [1].
• Polyclonal heparan sulfate antibodies were produced by immunizing rabbits with HSPG purified from the Engelbreth-Holm-Swarm mouse tumor; these antibodies stained rat intestinal basement membranes [2].
• Immunofluorescent staining with these antibodies allowed us to demonstrate that distribution of HSPG at the epithelial-mesenchymal interface varied with the stages of intestinal development, suggesting that remodeling of this proteoglycan is essential for regulating cell behavior during morphogenesis [2].
• However, the neurite outgrowth-promoting effect of AChE was strictly dependent upon the presence of substratum-bound heparan sulfate proteoglycans (HSPG) [3].
• Rather, the protein is localized in the extracellular matrix of theca externa cells, which produce this HSPG [4].

Biological context of HSPG

• Consistent with its ability to bind NCAM, we show that the intact 6D2 HSPG inhibits cell adhesion to a HBD peptide substratum, and also binds chick brain cells when employed as a substratum [5].
• Using monoclonal antibodies and a polyclonal antiserum to the core protein of a previously identified HSPG from embryonic chick brain, our expression screened a random-primed E9 chick brain cDNA library [6].

Anatomical context of HSPG

• In the present study we have identified the extracellular matrix protein agrin as a major heparan sulfate proteoglycan (HSPG) in embryonic chick brain [6].
• We also show that the anti-HSPG antibodies stain the synaptic site of the neuromuscular junction, in agreement with agrin expression [6].
• The spatiotemporal expression of syndecan-3 during feather development suggests that this cell-surface HSPG may be involved in the response of competent embryonic skin dermis to FGF-2 [7].

Associations of HSPG with chemical compounds

• In addition, adhesion inhibition experiments suggested a hitherto-undetected role for chondroitin sulfate proteoglycans in the stimulation of NCAM-mediated adhesion to some, but not all, of the HSPG ligands [8].
• During development the relative percentage of HSPG decreases from approximately 50% of total sulfate-labeled PG at E6 to 25% by E10 [5].
• Characteristics of the chondroitin sulfate/dermatan sulfate proteoglycans (CS/DSPGs) and heparan sulfate proteoglycans (HSPGs) from retinas of 14-day chicken embryos were examined following specific lyase digestion of the HSPG and CS/DSPG glycosaminoglycans, respectively [9].
• The 39-kDa core protein is anchored to the cell surface by a glycosyl phosphatidylinositol anchor as evidenced by 1) release of the HSPG with the 39-kDa core protein into media by PIPLC treatment and 2) biosynthetic incorporation of [3H]ethanolamine and [32P]orthophosphate into the PIPLC-releasable 39-kDa core protein [10].

Physical interactions of HSPG

• In the present study we have characterized the major proteoglycans of chick brain, focusing on their pattern of expression in development and on identifying the heparan sulfate proteoglycan (HSPG) that binds to the neural cell adhesion molecule (NCAM) [5].

Other interactions of HSPG

• Thus, our studies demonstrate that chick agrin is a HSPG that is prominent in the embryonic chick brain [6].
• Monospecific antibodies to purpurin and a heparan sulphate proteoglycan (HSPG), two components of adherons, labeled a subpopulation of junctions [11].

Analytical, diagnostic and therapeutic context of HSPG

• The deposition of intestinal heparan sulfate proteoglycan (HSPG) at the epithelial-mesenchymal interface and its cellular source have been studied by immunocytochemistry at various developmental stages and in rat/chick interspecies hybrid intestines [2].
• Immunoprecipitation experiments indicated that mAb 4C1 recognized the chicken basement membrane HSPG [2].
• The agrin immunoreactivity on the blot was shifted to a defined band of approximately 250 kDa after treatment of the samples with heparitinase or nitrous acid, and this banding pattern was indistinguishable from immunoreactivity obtained with antibodies to the brain HSPG [6].
• Western blot analysis and immunocytochemistry confirmed that agrin is a HSPG that is identical with the HSPG from embryonic chick brain [6].

References