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Receptor-mediated endocytosis of apamin by liver cells

Strong, P. N. and Evans, William Howard 1987. Receptor-mediated endocytosis of apamin by liver cells. European Journal of Biochemistry 163 (2) , pp. 267-273. 10.1111/j.1432-1033.1987.tb10797.x

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Abstract

The binding and uptake of the bee venom toxin apamin, by guinea-pig and rat liver were studied. Guinea-pig liver plasma membranes contain inhibitable, high-affinity binding sites for [125I]monoiodoapamin: Kd = 12.6 +/- 0.8 pM (SE); Bmax = 4.2 +/- 0.2 fmol/mg protein. No binding sites for [125I]monoiodoapamin on rat liver plasma membranes were detected in agreement with the absence of a physiological response to the toxin by rat hepatocytes. [125I]Monoiodoapamin, injected into the portal vein of guinea-pigs, was recovered in an undegraded form in a liver endosome fraction. The uptake of [125I]monoiodoapamin by rat livers was less than 4% of that taken up by guinea-pig livers and there was little evidence of radiolabelled toxin appearing in isolated rat endocytic vesicles. Inhibitable, high-affinity binding sites for [125I]monoiodoapamin were also identified on isolated guinea-pig liver endosomal membranes; Kd = 10.6 +/- 3.3 pM; Bmax = 2.5 +/- 0.6 fmol/mg protein. No inhibitable apamin binding sites were detected on rat endosomal membranes. Plasma membranes and endosomal membranes isolated from guinea-pig liver showed a similar spectrum of polypeptides to that previously reported for plasma membranes and endosomal membranes isolated from rat liver. The enzymatic composition of guinea-pig endosomes was also similar to that previously reported for rat endosomes. The results indicate that apamin was internalised by receptor-mediated endocytosis by guinea-pig liver cells in an analogous manner to that already shown for a variety of endogenous ligands.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Medicine
Subjects: R Medicine > R Medicine (General)
R Medicine > RZ Other systems of medicine
Publisher: Wiley
ISSN: 0014-2956
Last Modified: 17 Mar 2021 02:58
URI: http://orca.cardiff.ac.uk/id/eprint/66966

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