Influence of cytosolic pH on receptor-mediated endocytosis of asialoorosomucoid

A. C. Samuelson, R. J. Stockert, A. B. Novikoff, P. M. Novikoff, J. C. Saez, D. C. Spray, A. W. Wolkoff

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Abstract

Inhibitors of specific steps in the endocytosis of galactose-terminating glycoproteins (asialoglycoproteins) by cultured rat hepatocytes have been described (J. Cell Biol. 98: 375-381, 1984). In particular, substitution of K+ for Na+ in the culture medium results in reduced delivery of ligand to lysosomes; ligand-receptor internalization, dissociation, and segregation remain normal. We have now demonstrated by direct microelectrode measurement that incubation of hepatocytes in K+-substituted medium results in a reduction of intracellular pH by ≥0.5 U. In addition, we have shown that reduced intracellular pH in these cells produced by either (CO2 diffusion) or indirect (K+ substitution) acidification inhibits ligand delivery to lysosomes. Return of internalized ligand-receptor complex to the cell surface (diacytosis) is also inhibited by these manipulations. These studies suggest that intracellular pH may modulate specific steps involving vesicle translocation and fusion in the receptor-mediated endocytosis of asialoglycoproteins. Similar effects of direct acidification of hepatocytes by CO2 diffusion and indirect acidification by K+ substitution for Na+, on diacytosis and ligand delivery to lysosomes, suggest that K+ substitution may influence these events by altering intracellular pH.

Original languageEnglish (US)
Pages (from-to)23/6
JournalAmerican Journal of Physiology - Cell Physiology
Volume254
Issue number6
Publication statusPublished - Jan 1 1988

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ASJC Scopus subject areas

  • Physiology
  • Cell Biology

Cite this

Samuelson, A. C., Stockert, R. J., Novikoff, A. B., Novikoff, P. M., Saez, J. C., Spray, D. C., & Wolkoff, A. W. (1988). Influence of cytosolic pH on receptor-mediated endocytosis of asialoorosomucoid. American Journal of Physiology - Cell Physiology, 254(6), 23/6.