Diacytosis of human asialotransferrin type 3 by isolated rat hepatocytes

H Tolleshaug, P A Chindemi, E Regoeczi
1981 Journal of Biological Chemistry  
In suspensions of freshly isolated hepatocytes, asialotransferrin type 3 became rapidly bound by the asialoglycoprotein-binding hepatic lectin. Suspended hepatocytes, just as the liver of intact animals, catabolized asialotransferrin in a concentration-dependent manner. At low asialotransferrin concentrations (0.4-1 nM), the fraction of labeled protein degraded was much smaller than found with comparable concentrations of asialofetuin in an earlier study (Tolleshaug, H., Berg, T., Nilsson, M.,
more » ... nd Norum, K. R. (1977) Biochim. Biophys. Acta 499, 73-84). The fraction of endocytosed asialotransferrin that was degraded, could, however, be substantially increased by raising the concentration of asialotransferrin the medium. Release studies using a chelating agent or competitive inhibitors of the binding reaction showed that at low asialotransferrin concentrations, hepatocytes exocytose the preponderance of the intracellular asialotransferrin with a half-life of approximately 20 min. This novel observation raises the possibility that lysosomal homing of an endosome transporting asialoglycoprotein requires an intracellular target signal.
pmid:7240224 fatcat:z3veedyx4bd2jnh4bukhmkocxe