To assess the role of microfilaments in receptor-mediated endocytosis of asialoglycoproteins, hepatocytes isolated from adult and 6-day-old rats were treated with the antimicrofilamentous agent cytochalasin D and then incubated with 125I-asialoorosomucoid (ASOR). Cytochalasin D (50 μM) reduced degradation of continuously endocytosed ASOR (7.5 μg/ml) equally in adult and neonate to ~ 20% of control. Internalization of surface-bound ASOR suggested at least two discrete sites at which ligand translocation was inhibited by drug at both ages: 1) initial movement of receptor-ligand complex from cell surface to interior and 2) postinternalization ligand transit to lysosomes. Inhibition of plasma membrane translocation was confirmed by calculation of endocytotic rate constant (K(e)) values, which were decreased to ~ 20-30% of control after cytochalasin D treatment. In contrast, the antimicrotubular drug colchicine did not reduce K(e) values significantly nor did colchicine in combination with cytochalasin D impede lysosome-directed transport more than cytochalasin D alone. These results indicate that internalization of occupied asialoglycoprotein surface receptor is microfilament dependent irrespective of postnatal age and that subsequent participation of microfilaments in asialoglycoprotein trafficking is closely related to that of microtubules.
|Original language||English (US)|
|Journal||American Journal of Physiology - Gastrointestinal and Liver Physiology|
|Issue number||4 22-4|
|State||Published - 1990|
- protein trafficking
ASJC Scopus subject areas
- Physiology (medical)