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E Brandan

Publications and source records attributed to E Brandan.

44 records · Page 3Linked to original sources
PubMed1986

The synaptic form of acetylcholinesterase binds to cell-surface heparan sulfate proteoglycans.

We have previously communicated that heparan sulfate and heparin released 16S acetylcholinesterase (AChE) from cholinergic synapses. These experiments suggest that heparan-like molecules are involved in the anchorage of AChE to the neuromuscular junction. In order to prove the in vivo interaction between the 16S AChE and heparan sulfate residues, the binding of exogenously added 16S enzyme to intact cells rich in cell-surface heparan sulfate proteoglycans was examined; 16S AChE form was shown to bind to intact endothelial cells in a specific, time-dependent, saturable fashion. A single class of binding sites was involved and at saturation around 2.52 X 10(11) molecules of 16S AChE/cm2 were bound. Fifty percent of the binding of the 16S AChE was blocked by heparan sulfate, heparin, or previous treatment of the cell with heparitinase. The binding was reversed by exogenous heparin, but not by chondroitin sulfate or hyaluronic acid. Our results demonstrate that the synaptic form of AChE binds to heparan sulfate proteoglycans on the surface of the cell.

Acetylcholinesterase↗
PubMed1985

Anchorage of collagen-tailed acetylcholinesterase to the extracellular matrix is mediated by heparan sulfate proteoglycans.

Heparan sulfate and heparin, two sulfated glycosaminoglycans (GAGs), extracted collagen-tailed acetylcholinesterase (AChE) from the extracellular matrix (ECM) of the electric organ of Discopyge tschudii. The effect of heparan sulfate and heparin was abolished by protamine; other GAGs could not extract the esterase. The solubilization of the asymmetric AChE apparently occurs through the formation of a soluble AChE-GAG complex of 30S. Heparitinase treatment but not chondroitinase ABC treatment of the ECM released asymmetric AChE forms. This provides direct evidence for the vivo interaction between asymmetric AChE and heparan sulfate residues of the ECM. Biochemical analysis of the electric organ ECM showed that sulfated GAGs bound to proteoglycans account for 5% of the total basal lamina. Approximately 20% of the total GAGs were susceptible to heparitinase or nitrous acid oxidation which degrades specifically heparan sulfates, and approximately 80% were susceptible to digestion with chondroitinase ABC, which degrades chondroitin-4 and -6 sulfates and dermatan sulfate. Our experiments provide evidence that asymmetric AChE and carbohydrate components of proteoglycans are associated in the ECM; they also indicate that a heparan sulfate proteoglycan is involved in the anchorage of the collagen-tailed AChE to the synaptic basal lamina.

Acetylcholinesterase↗
PubMed1984

Binding of the asymmetric forms of acetylcholinesterase to heparin.

The interaction between acetylcholinesterase (EC 3.1.1.7) and heparin, a sulphated glycosaminoglycan, was studied by affinity chromatography. A specific binding of the asymmetric acetylcholinesterase to an agarose gel containing covalently bound heparin was demonstrated. This interaction required an intact collagenous tail, shown by the fact that the binding is abolished by pretreatment with collagenase. The globular forms did not bind to the column. Both total and intracellular asymmetric acetylcholinesterase forms isolated from the endplate region of the rat diaphragm muscle showed higher affinity for the heparin than did the enzyme from the non-endplate region. The binding to the resin was destabilized with 0.55 M-NaCl, and, among the various glycosaminoglycans tested, only heparin was able to displace the acetylcholinesterase bound to the column. Our results added further support to the concept that the asymmetric acetylcholinesterase forms are immobilized on the synaptic basal lamina via interactions with heparin-like molecules, probably related to heparan sulphate proteoglycans.

Acetylcholinesterase↗
PubMed1982

Orientation and role of nucleosidediphosphatase and 5'-nucleotidase in Golgi vesicles from rat liver.

The fate of UDP formed during the galactosylation of added N-acetylglucosamine in Golgi vesicles isolated from rat liver using D2O-sucrose gradients has been determined. UDP-Gal labeled with [14C]uracil was used, and the products of the reaction were separated and quantitated by using high-pressure liquid chromatography. [14C]Uridine rather than [14C]UDP or [14C]UMP was found to accumulate, indicating the presence of both UDPase and UMPase activities in the Golgi. Golgi vesicles were shown to contain a nucleosidediphosphatase activity that is membrane bound. It appears to be located on the luminal face of the Golgi since it is activated 3-5-fold by detergents and 4-fold by treatment of the vesicles with Filipin. We have shown previously that Filipin disrupts the Golgi but does not solubilize membrane-bound enzymes. The nucleosidediphosphatase of the Golgi differs from that present in rough endoplasmic reticulum in its absolute requirement for Ca2+ for activity and in its substrate specificity that is higher for UDP than for IDP. Golgi vesicles also contain UMPase activity that is stimulated only 2-fold by detergents or Filipin. Concanavalin A inhibits this activity about 80% in both intact and detergent-treated vesicles. The Golgi UMPase is thus probably identical with 5'-nucleotidase. These results are consistent with histochemical evidence from other laboratories that indicate that 5'-nucleotidase is present on both sides of liver Golgi membranes. In the presence of concanavalin A and N-acetylglucosamine, intact Golgi vesicles were found to convert UDP-Gal to UMP. These findings indicate that UDP formed by galactosyltransferase in the lumen of the vesicles is rapidly converted to UMP by UDPase in the lumen but that UMP moves rapidly out of the lumen of the Golgi and is broken down to uridine by 5'-nucleotidase on the cytoplasmic side of the vesicles.

5'-Nucleotidase↗