Appican, the Proteoglycan Form of the Amyloid Precursor Protein, Contains Chondroitin Sulfate E in the Repeating Disaccharide Region and 4-O-Sulfated Galactose in the Linkage Region (original) (raw)
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The Journal of Neuroscience : The Official Journal of the Society for Neuroscience
Appicans are secreted or cell-associated brain chondroitin sulfate proteoglycans produced by glia cells and containing Alzheimer amyloid precursor protein (APP) as a core protein. Here, we report that rat C6 glioma cells transfected with appican displayed a dramatic change in their phenotypic appearance compared with untransfected cells or cells transfected with APP. Appicantransfected cells lost the round appearance of the untransfected control C6 cells, acquired a flat morphology, and elaborated more processes than control cells. Untransfected, or APP-transfected C6, cells were completely dissociated from their substrate after 40 min of treatment with cell dissociation solution. Under the same conditions, however, Ͻ20% of the appican-transfected C6 cells were dissociated from their substrate, suggesting that the appican-transfected glia cells attach more avidly to their substrate than do untransfected or APP transfected control cells. In contrast, appican-transfected fibroblast cells showed no morphological changes and dissociated from their substrate similarly to untransfected fibroblast cells. Extracellular matrix (ECM) prepared from appican-transfected C6 cell cultures contained high levels of appican and was a significantly better substrate for the attachment of C6 cells than ECM from either untransfected or APPtransfected cultures. Furthermore, cell adhesion to ECM was independent of the level of appican expression of the plated cells. ECM from appican-transfected C6 cultures stimulated adhesion of other neural cells including primary astrocytes, Neuro2a neuroblastoma, and PC12 pheochromocytoma, but not fibroblast cells. Conditioned media from appican-transfected C6 cultures failed to promote cell adhesion. Together, these data suggest that secreted appican incorporates into ECM and promotes adhesion of neural cells. Furthermore, our data suggest that the chondroitin sulfate chain engenders APP with novel biological functions.
Chondroitin sulfate proteoglycan form of cellular and cell-surface Alzheimer amyloid precursor
Neuroscience Letters, 1993
The biological function of the amyloid precursor protein (APP) is still not fully understood. Recently, we reported that secreted truncated APP occurs in a chondroitin sulfate proteoglycan form. Here we present evidence that full length APP-chondroitin sulfate proteoglycan is present on the cell surface of C6 glioma cells. In addition, densitometric quantitation of Western blots showed that approximately 50% of the mature cell-associated full length APP is in the proteoglycan form. These findings suggest that the proteoglycan nature of APP may be important for the implementation of its biological function.
Chondroitin sulfate proteoglycan form of the Alzheimer's β-Amyloid precursor
Journal of Biological Chemistry
The Alzheimer's amyloid beta protein is derived from a family of membrane glycoproteins termed amyloid precursor proteins (APP). Here we show that APP exists as the core protein of a chondroitin sulfate (CS) proteoglycan, ranging in apparent molecular size from 140 to 250 kDa, secreted by glial cell line C6. After partial purification on ion-exchange and gel chromatography, the secreted APP proteoglycan was recognized on Western blots by several antibodies specific to different regions of APP. Chondroitinase AC or ABC treatment of our samples completely eliminated the high molecular weight proteoglycan with a concomitant increase in the APP protein. This digested product reacted with an anti-stub antibody which recognizes 4-sulfated disaccharide. Sequencing of the N terminus of the core protein of this CS proteoglycan yielded 18 residues identical to the N terminus sequence of the mature APP. Quantitative analysis showed that, in this cell line, about 90% of the secreted nexin I...
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1997
Appicans are secreted or cell-associated brain chondroitin sulfate proteoglycans produced by glia cells and containing Alzheimer amyloid precursor protein (APP) as a core protein. Here, we report that rat C6 glioma cells transfected with appican displayed a dramatic change in their phenotypic appearance compared with untransfected cells or cells transfected with APP. Appican-transfected cells lost the round appearance of the untransfected control C6 cells, acquired a flat morphology, and elaborated more processes than control cells. Untransfected, or APP-transfected C6, cells were completely dissociated from their substrate after 40 min of treatment with cell dissociation solution. Under the same conditions, however, <20% of the appican-transfected C6 cells were dissociated from their substrate, suggesting that the appican-transfected glia cells attach more avidly to their substrate than do untransfected or APP transfected control cells. In contrast, appican-transfected fibroblas...
Glycosylation Site for Chondroitin Sulfate on the Neural Part-time Proteoglycan, Neuroglycan C
Journal of Biological Chemistry, 2004
Neuroglycan C (NGC) is a membrane-spanning chondroitin sulfate (CS) proteoglycan that is expressed predominantly in the central nervous system (CNS). NGC dramatically changed its structure from a proteoglycan to a nonproteoglycan form with cerebellar development, whereas a small portion of NGC molecules existed in a nonproteoglycan form in the other areas of the mature CNS, suggesting that the CS glycosylation of NGC is developmentally regulated in the whole CNS. As primary cultured neurons and astrocytes from cerebral cortices expressed NGC in a proteoglycan form and in a nonproteoglycan form, respectively, CS glycosylation seems to be regulated differently depending on cell type. To investigate the glycosylation process, cell lines expressing a proteoglycan form of NGC would be favorable experimental models. When a mouse NGC cDNA was transfected into COS 1, PC12D, and Neuro 2a cells, only Neuro 2a cells, a mouse neuroblastoma cell line, expressed NGC bearing CS chains. In PC12D cells, although three intrinsic CS proteoglycans were detected, exogenously expressed NGC did not bear any short CS chains just like NGC in the mature cerebellum. This suggests that the addition of CS chains to the NGC core protein is regulated in a manner different from that of other CS proteoglycans. As the first step in investigating the CS glycosylation mechanism using Neuro 2a cells, we determined the CS attachment site as Ser-123 on the NGC core protein by site-directed mutagenesis. The CS glycosylation was not necessary for intracellular trafficking of NGC to the cell surface at least in Neuro 2a cells.
Isolation of a neural chondroitin sulfate proteoglycan with neurite outgrowth promoting properties
The Journal of Cell Biology, 1994
Proteoglycans are expressed in various tissues on cell surfaces and in the extracellular matrix and display substantial heterogeneity of both protein and carbohydrate constituents. The functions of individual proteoglycans of the nervous system are not well characterized, partly because specific reagents which would permit their isolation are missing. We report here that the monoclonal antibody 473HD, which binds to the surface of early differentiation stages of murine astrocytes and oligodendrocytes, reacts with the chondroitin sulfate/dermatan sulfate hybrid epitope DSD-1 expressed on a central nervous system chondroitin sulfate proteoglycan designated DSD-1-PG. When purified from detergent-free postnatal days 7 to 14 mouse brain extracts, DSD-1-PG displays an apparent molecular mass between 800-1,000 kD with a prominent core glycoprotein of 350-400 kD. Polyclonal anti-DSD-1-PG antibodies and monoclonal antibody 473HD react with the same molecular species as shown by immunocytochemistry and sequential immunoprecipitation performed on postnatal mouse cerebellar cultures, suggesting that the DSD-1 epitope is restricted to one proteoglycan. DSD-1-PG promotes neurite outgrowth of embryonic day 14 mesencephalic and embryonic day 18 hippocampal neurons from rat, a process which can be blocked by monoclonal antibody 473HD and by enzymatic removal of the DSD-1-epitope. These results show that the hybrid glycosaminoglycan structure DSD-1 supports the morphological differentiation of central nervous system neurons.