PG-M/Versican-like Proteoglycans Are Components of Large Disulfide-stabilized Complexes in the Axolotl Embryo

Abstract

Large disulfide-stabilized proteoglycan complexes were previously shown to be synthesized by the epidermis of axolotl embryos during stages crucial to subepidermal migration of neural crest cells. We now show that the complexes contain PG-M/versican-like monomers in addition to some other component with low buoyant density. Metabolically 35 S-labeled proteoglycans were extracted from epidermal explants and separated by size exclusion chromatography and density equilibrium gradient centrifugation. The complexes, which elute in the void volume on Sepharose CL-2B, were recovered at buoyant density 1.42 g/ml in CsCl gradients, whereas the monomer proteoglycans, which could only be liberated from the complexes by reduction, had a higher buoyant density (1.48 g/ml). The native complexes did not aggregate with hyaluronan. The purified complexes reacted with antibodies against a portion of a cloned PG-M/versican-like axolotl proteoglycan. These antibodies were found to stain the subepidermal matrix of axolotl embryos, suggesting that the proteoglycan complexes are encountered by neural crest cells during subepidermal migration. From Western blot analysis, the core protein of the PG-M/versicanlike monomers was found to be of similar size (Ϸ500 kDa) as those of PG-M/versican variants of other species. Another chondroitin sulfate proteoglycan that was present in small amounts in the epidermal extracts was found to be distinctly different from the similarly sized PG-M/versican-like monomers.The role of proteoglycans (PGs) 1 in the modulation of cellmatrix interaction and cell migration depends on their structure and localization (1-3). Interstitial PGs that carry chondroitin/dermatan sulfate (CS/DS) chains have been implicated to have such modulatory roles by several studies (4 -18). In this regard, since both the core protein (7, 18 -19) and the glycosaminoglycan moiety (15,18,20) appear to be of functional importance, the structure of the intact PG may be crucial (9,18). In addition to the inherent potential for heterogeneity in the carbohydrate component (21), the core proteins of PGs in the PG-M/versican family, for instance, may exist as several splice variants (22-25) with potentially diverse expression patterns and functions during various stages of the life cycle of an animal.The importance of the extracellular matrix in the regulation of subepidermal neural crest cell migration in the axolotl embryo was demonstrated by transplantation experiments in which epidermal grafts or microcarriers with matrix adsorbed in situ from developmentally more advanced embryos were found to trigger the onset of premature migration (26). Ultrastructural studies of the matrix after fixation in the presence of cetylpyridinium chloride (27) or ruthenium red (28 -30) revealed an abundance of granular proteoglycan precipitates along collagen fibrils. Interestingly, in embryos of the white mutant axolotl, in which subepidermal migration of the neural crest-derived pigment cells is defective (28 -29, 31), the subepidermal matrix was sign...

Promotion of chondrocyte proliferation by versican mediated by G1 domain and EGF-like motifs

“…The large chondroitin sulfate proteoglycan versican was initially described in human fibroblasts [Zimmermann and Ruoslahti, 1989] and was then found in a variety of tissues [Yamagata et al, 1993b;Yao et al, 1994;Nara et al, 1997;Stigson et al, 1997;du Cros et al, 1995]. The tissues that contain versican include embryonic tissues such as embryonic lung fibroblasts [Zimmerman and Ruoslahti, 1989]; embryonic aorta, cornea, and skeletal muscle [Yamagata et al, 1993b]; the mesenchymal cell condensation area of limb buds [Kimata et al, 1986;Shinomura et al, 1990]; the perinotochordal Fig.…”

β1-Integrin-mediated Glioma Cell Adhesion and Free Radical-induced Apoptosis Are Regulated by Binding to a C-terminal Domain of PG-M/Versican

“…PG-M/versican was originally isolated from human fibroblasts and chicken developing limb buds (10 -14) and was later detected in the normal human central nervous system and brain tumors (15)(16)(17). This proteoglycan is made up of a hyaluronan-binding N terminus (G1 domain) and a selectin-like C terminus (G3 domain) with a central sequence for glycosaminoglycan chain modification (14,18,19).…”

Inhibition of Scleral Proteoglycan Synthesis Blocks Deprivation-induced Axial Elongation in Chicks

“…8(C) suggests a greater reduction in aggrecan core protein in CL-2B column fractions of the xyloside treated sclera than in the glycosaminoglycan content in the same fractions. One explanation for this apparent discrepancy is that since the DMMB assay measures total sulfated glycosaminoglycans, it is possible that other proteoglycans, such as versican or perlecan, which co-elute from CL-2B with aggrecan (Keller et al, 1987, Stigson, Lofberg andKjellen, 1997) may be less effected by xyloside treatment and might reduce the differences in glycosaminoglycan concentration between the xyloside and control scleral extracts. Additionally, it is possible that the sulfation of aggrecan is altered (i.e.…”