Hypoxia induces NO-dependent release of heparan sulfate in fibroblasts from the Alzheimer mouse Tg2576 by activation of nitrite reduction

There is a functional relationship between the heparan sulfate proteoglycan glypican-1 and the amyloid precursor protein (APP) of Alzheimer disease. In wild-type mouse embryonic fibroblasts, expression and processing of the APP is required for endosome-to-nucleus translocation of anhydromannose-containing heparan sulfate released from S-nitrosylated glypican-1 by ascorbate-induced, nitrosothiol-catalyzed deaminative cleavage. In fibroblasts from the transgenic Alzheimer mouse Tg2576, there is increased processing of the APP to amyloid-β peptides. Simultaneously, there is spontaneous formation of anhydromannose-containing heparan sulfate by an unknown mechanism. We have explored the effect of hypoxia on anhydromannose-containing heparan sulfate formation in wild-type and Tg2576 fibroblasts by deconvolution immunofluorescence microscopy and flow cytometry using an anhydromannose-specific monoclonal antibody and by 35SO4-labeling experiments. Hypoxia prevented ascorbate-induced heparan sulfate release in wild-type fibroblasts, but induced an increased formation of anhydromannose-positive and 35S-labeled heparan sulfate in Tg2576 fibroblasts. This appeared to be independent of glypican-1 S-nitrosylation as demonstrated by using a monoclonal antibody specific for S-nitrosylated glypican-1. In hypoxic wild-type fibroblasts, addition of nitrite to the medium restored anhydromannose-containing heparan sulfate formation. The increased release of anhydromannose-containing heparan ...
Source: Glycobiology - Category: Biology Authors: Tags: Cell Biology Source Type: research