title: Cycling of the integral membrane glycoprotein, LEP100, between plasma membrane and lysosomes: kinetic and morphological analysis.
abstract: LEP100 (an integral membrane glycoprotein, Mr = 100,000) occurs in three subcellular compartments: lysosome (approximately 90% of the molecules), endosome (5%-8%), and plasma membrane (2%-3%). Rate constants for movement to and from each compartment have been estimated. The movement of LEP100 from endosomes to lysosomes was blocked by chloroquine, causing redistribution to a new steady state in which about 30% of LEP100 molecules were localized in clathrin-coated patches on the cell surface, while intracellular LEP100 occurred in nearby endocytic vesicles. The cell-surface and endosomal pools of LEP100 remained in rapid equilibrium (t1/2 about 5 min). These results support the existence of a hitherto unappreciated pathway of membrane flow from lysosomes. The lysosome should not be considered simply a terminal target of membrane trafficking.
mesh_terms: D000818:Animals; D030161:Avian Proteins; D002462:Cell Membrane / Q000378:metabolism*; D002645:Chickens; D002738:Chloroquine / Q000494:pharmacology; D002966:Clathrin / Q000494:pharmacology; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D007700:Kinetics; D008247:Lysosomes / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008985:Monensin / Q000494:pharmacology
chemical_list: D030161:Avian Proteins; D002966:Clathrin; D008562:Membrane Glycoproteins; C066541:LEP100 protein, Gallus gallus; D002738:Chloroquine; D008985:Monensin