Evidence for an immunological and functional relationship between superoxide dismutase and a high molecular weight osteoclast plasma membrane glycoprotein

1991 ◽  
Vol 46 (4) ◽  
pp. 331-344 ◽  
Author(s):  
Merry Jo Oursler ◽  
Patricia Collin-Osdoby ◽  
Ling Li ◽  
Earlene Schmitt ◽  
Philip Osdoby
Keyword(s):  
Molecular Weight ◽  
Superoxide Dismutase ◽  
Plasma Membrane ◽  
High Molecular Weight ◽  
Functional Relationship ◽  
Membrane Glycoprotein

CA2+-INDUCED STRUCTURAL TRANSITIONS OF THE PLATELET GP IIb-IIIa COMPLEX

1987 ◽  
Author(s):  
B Steiner ◽  
D R Phillips
Keyword(s):  
Molecular Weight ◽  
Platelet Aggregation ◽  
High Molecular Weight ◽  
Functional Activity ◽  
Sucrose Gradient ◽  
Membrane Glycoprotein ◽  
Structural Transitions ◽  
Heterodimeric Complex ◽  
Triton X ◽  
Active Subunits

Previous studies have shown that the membrane glycoprotein (GP) IIb-IIIa complex can be reversibly dissociated by incubating platelets for 5 min at 37°C in an EDTA-containing buffer. Prolonged incubations (30 min) with EDTA, however, result in the formation of high molecular weight aggregates of GP IIb and GP IIIa. These aggregates of individual GP's neither bind fibrinogen nor support platelet aggregation, indicating that chelation of Ca2+ can affect the functional activity of GP IIb-IIIa. The present study was designed to identify conditions for the generation of functionally active GP IIb and GP IIIa. Functionally active subunits were defined as those which reformed GP IIb-IIIa complexes. The complexes were quantified by sucrose gradient sedimentation (complexed, dissociated and aggregated GP’s have different sedimentation coefficients) and thrombin hydrolysis (dissociated and aggregated GP lib are susceptible to hydrolysis by thrombin while GP lib in the GP IIb-IIIa complex is thrombin resistant). Purified GP IIb-IIIa could be dissociated by a 5 min incubation at 37°C with ≤ 10−5 M Ca2+. When the complexes were dissociated in the presence of Ca2+ concentrations below 10−6 m, the monomeric GP IIIa was converted to a slower sedimenting form; this change in structure caused it to become functionally inactive. In the presence of very low Ca2+ concentrations 10−6 M) both dissociated subunits subsequently formed high molecular weight aggregates. However, these changes in structure and loss in function could be prevented by dissociating the complexes in 10−6 M Ca2+ and immediately readding raM Ca2+ at 4°C. When this solution was warmed to 20°C, almost 70% of the dissociated subunits reformed heterodimeric complexes. Storage at 4°C for as long as 6 h did not alter the functional activity of these subunits. Octylglucoside, but not Triton X-100, completely inhibited reassociation. Experiments performed in the presence of various H+ and salt concentrations showed that the interactive forces between GP IIb and GP IIIa are both electrostatic and hydrophobic. Thus, conditions have been obtained for the preparation of functionally active GP IIb and GP IIIa which can reform the native heterodimeric complex. Various Ca2+ concentrations can have multiple effects on the structure of the dissociated subunits.

scholarly journals High molecular weight amyloid β 1‐42 oligomers induce neurotoxicity via plasma membrane damage

2019 ◽  
Vol 33 (8) ◽  
pp. 9220-9234 ◽  
Author(s):  
Taro Yasumoto ◽  
Yusaku Takamura ◽  
Mayumi Tsuji ◽  
Takahiro Watanabe‐Nakayama ◽  
Keiko Imamura ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Plasma Membrane ◽  
High Molecular Weight ◽  
Membrane Damage ◽  
Amyloid Β ◽  
Plasma Membrane Damage

Effect of altered oligosaccharide structure on the cell surface number, distribution and turnover of the high molecular weight acidic glycoproteins of CHO cells

1984 ◽  
Vol 67 (1) ◽  
pp. 1-23
Author(s):  
L.A. Fitzgerald ◽  
J.B. Denny ◽  
G.A. Baumbach ◽  
C.M. Ketcham ◽  
R.M. Roberts
Keyword(s):  
Molecular Weight ◽  
Plasma Membrane ◽  
High Molecular Weight ◽  
Cho Cells ◽  
Carbohydrate Structure ◽  
Membrane Glycoproteins ◽  
Number Distribution ◽  
Mutant Lines ◽  
Mutant Cells ◽  
Surface Glycoproteins

The influence of altered carbohydrate structure on the surface number, distribution and turnover of plasma membrane glycoproteins has been studied in Chinese hamster ovary (CHO) cells by comparing three lines that are resistant to the cytotoxic effects of wheat germ agglutinin (WGA) with parental CHO cells. The glycoproteins investigated were members of a group of high molecular weight acidic glycoproteins (HMWAG). On parental cells these represent the major surface components that become labelled by lactoperoxidase-catalysed iodination. They are the only plasma membrane glycoproteins that bind WGA. The mutant lines also possess iodinatable surface polypeptides of high molecular weight, but these were less acidic and electrophoretically less diffuse than those from parental cells. These polypeptides in general did not bind [125I]WGA when two-dimensional polyacrylamide gels were overlaid with iodinated lectin. Mutant cells treated with fluorescein-conjugated WGA showed low surface fluorescence. However, the nuclear envelope and a small region in the perinuclear zone fluoresced strongly. Together, these results confirm that the surface glycoproteins of mutant cells had altered carbohydrate structure. Mouse antiserum prepared against the HMWAG, however, bound equally effectively to the mutant lines as to the parental lines. Indirect immunofluorescence experiments showed that the HMWAG had a fairly uniform distribution over the surface, and that internalization induced by second antibody occurred at a similar rate and in a similar manner in all lines, including the mutants. Electron microscopic observations using immunoperoxidase procedures confirmed the similarities in glycoprotein distribution on mutant and parental cells. Two mouse monoclonal antibodies raised against the HMWAG also revealed no difference in the number or topography of surface glycoproteins. Finally, the half-lives of several HMWAG in a parental and a mutant line (15B) maintained on low-serum medium were compared by means of a 125I/131I double-label technique. Half-lives of HMWAG from the former averaged 12 h and from the latter 11 h. It is concluded that the lack of complex termini on oligosaccharides of this particular group of CHO plasma membrane glycoproteins has no effect on their number, distribution or turnover.

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