The Biochemistry and physiology of the endocytic apparatus

Update Item Information
Title The Biochemistry and physiology of the endocytic apparatus
Publication Type dissertation
School or College School of Medicine
Department Pathology
Author Ajioka, Richard Scott
Date 1987-06
Description Cells have evolved a number of specialized mechanisms to transport molecules across the plasma membrane barrier. Endocytic processes involve the invagination and internalization of membrane vesicles and their contents. Conversely, secretory events involve fusion of membrane vesicles with the plasma membrane. The net effect of such activities is the mixing of intracellular and plasma membrane components. Cells must therefore posses some type of sorting mechanism to counteract this randomization and it is believed that the endocytic pathway plays a part in sorting internalized membrane and its constituents. The present study made use of a specific tracer molecule to analyze the compartments involved in the endocytosis/recycling pathway. Transferrin and the transferrin receptor were used to study the endocytic pathway because this ligand along with its receptor traverses the entire endocytic and recycling pathway without being degraded. Transferrin was chemically coupled to horseradish peroxidase in order to specifically target peroxidase activity to the endocytic apparatus. Peroxidase can be used to alter the physical properties of compartments containing the enzyme by affecting an increase in buoyant density, and a crosslinking of luminal contents. The density shift procedure was used to demonstrate that transferrin, low density lipoprotein, and epidermal growth factor are internalized into the same endocytic compartment. A combination of the density shift and crosslinking reactions was used to determine that the endocytic pathway responsible for the accumulation of ligand does not include the Golgi apparatus. Use of the conjugate also provided a means to study the movement of unoccupied receptors. It was determined that intracellular transferrin receptors in HeLa cells are the result of the constitutive internalization of unoccupied receptors. It was further demonstrated that endocytic compartments internalized at different times remain temporally segregated. These results suggest that one way in which surface receptor number can be regulated is the by rate of internalization of unoccupied receptors. The results of the present studies provide a quantitative approach to describing the nature and constituents of the endocytic/recycling pathway. They provide strong support for the notion that the endosome is the intracellular organelle responsible for sorting different receptor/ligand complexes and raise the possibility that this organelle may also participate in the regulation of plasma membrane proteins. Further, these studies provide a method and conceptual approach for further experimentation on the role of the endosome in cellular physiology and metabolism.
Type Text
Publisher University of Utah
Subject Cell Membrane; Endocytosis; Endosomes
Subject MESH Biological Transport; Cell Membrane Permeability
Dissertation Institution University of Utah
Dissertation Name PhD
Language eng
Relation is Version of Digital reproduction of "The Biochemistry and physiology of the endocytic apparatus." Spencer S. Eccles Health Sciences Library. Print version of "The Biochemistry and physiology of the endocytic apparatus." available at J. Willard Marriott Library Special Collection. QH 9.7 1987 A39.
Rights Management © Richard Scott Ajioka.
Format application/pdf
Format Medium application/pdf
Format Extent 2,080,884 bytes
Identifier undthes,5460
Source Original: University of Utah Spencer S. Eccles Health Sciences Library (no longer available).
Funding/Fellowship National Institutes of Health predoctroal training grants 5T32GM07464-08 and 5T32GM0746409
Master File Extent 2,080,933 bytes
ARK ark:/87278/s6ws8w1r
Setname ir_etd
ID 190715
Reference URL https://collections.lib.utah.edu/ark:/87278/s6ws8w1r
Back to Search Results