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Import of the polyamine spermine from the extracellular environment depends on the presence of cell surface heparan sulfate proteoglycans, such as glypican-1. This proteoglycan is internalized by endocytosis, releases its heparan sulfate chains in endosomes by a nitric oxide-, copper- and amyloid precursor protein-dependent mechanism, then penetrates the membrane and is transported to the nucleus and then to autophagosomes. This process is spontaneous or induced by ascorbate depending on the growth-state of the cell. Here, we have explored possible connections between the heparan sulfate traffic route and spermine uptake and delivery in wild-type and Tg2576 mouse fibroblasts. Cells were examined by deconvolution immunofluorescence microscopy. The antibodies used were specific for spermine, glypican-1-derived heparan sulfate, Rab7, nucleolin and a marker for autophagosomes. Endogenous immunostainable spermine was primarily associated with autophagosomes. When spermine synthesis was inhibited, imported spermine appeared in Rab7-positive endosomes. When ascorbate was added, heparan sulfate and spermine were transported to the nucleus where they colocalized with nucleolin. Spermine also appeared in autophagosomes. In a pulse-chase experiment, heparan sulfate and spermine were first arrested in late endosomes by actinomycin D treatment. During the chase, when arrest was abolished, heparan sulfate and spermine were both transported to the nucleus and targeted nucleolin. In amyloid precursor protein-/--fibroblasts, ascorbate failed to induce release of heparan sulfate and spermine remained in the endosomes. We propose that cell surface glypican-1 carries spermine to the endosomes and that the released heparan sulfate carries spermine across the membrane into the cytosol and then to the nucleus.
This article was published in the following journal.
Name: Experimental cell research
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An enzyme that catalyzes the transfer of the propylamine moiety from 5'-deoxy-5'-S-(3-methylthiopropylamine)sulfonium adenosine to spermidine in the biosynthesis of spermine. It has an acidic isoelectric point at pH 5.0. EC 188.8.131.52.
Accidents on streets, roads, and highways involving drivers, passengers, pedestrians, or vehicles. Traffic accidents refer to AUTOMOBILES (passenger cars, buses, and trucks), BICYCLING, and MOTORCYCLES but not OFF-ROAD MOTOR VEHICLES; RAILROADS nor snowmobiles.
A biogenic polyamine formed from spermidine. It is found in a wide variety of organisms and tissues and is an essential growth factor in some bacteria. It is found as a polycation at all pH values. Spermine is associated with nucleic acids, particularly in viruses, and is thought to stabilize the helical structure.
A tyrosine phosphoprotein that plays an essential role in CAVEOLAE formation. It binds CHOLESTEROL and is involved in LIPIDS transport, membrane traffic, and SIGNAL TRANSDUCTION.
A genus of FUNGI, in the family Thelohaniidae, a parasite of red imported fire ants, MOSQUITOES, and other organisms.
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