Biomaterial Database

The role of ricin B chain in the intracellular trafficking of anti-CD5 immunotoxins. 1989

J M Manske, and D J Buchsbaum, and D A Vallera

Department of Therapeutic Radiology, University of Minnesota, Minneapolis 55455.

The mAb anti-CD5 was linked to purified ricin A chain (RTA) or intact ricin (Rc) containing B chain to determine the role of ricin B chain in the intracellular trafficking of anti-CD5 immunotoxins (IT). IT were radiolabeled with iodine-125 and then studied for their subcellular compartmentalization in an acute lymphoblastic leukemia T cell line, CEM. Ricin A chain IT was not as toxic to CEM cells as Rc-IT in protein synthesis inhibition assays. This difference was not attributed to differential binding or modulation of the CD5 determinant from the cell surface as measured by FACS analysis. However, we found a relationship between the toxicity of anti-CD5-Rc and anti-CD5-RTA and their ability to traffic to CEM lysosomes. Kinetic analysis of the transfer of radioimmunotoxin to the lysosomes showed that anti-CD5-Rc was trafficked significantly more slowly than anti-CD5-RTA, perhaps due to an extended period of time in the Golgi compartment. The possibility of a Golgi interaction was tested by adding monensin, a carboxylic ionophore that interrupts trafficking through the Golgi, to cells treated with anti-CD5-RTA. The addition of monensin caused anti-CD5-RTA to traffic in a manner identical to anti-CD5-Rc. We conclude that 1) B chain slows trafficking of anti-CD5-Rc to the lysosomes; 2) the rate-limiting step in the toxicity difference between anti-CD5-Rc and anti-CD5-RTA is the rate of transfer to the lysosomes; and 3) trafficking through the Golgi may be important for anti-CD5-IT toxicity.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008247	Lysosomes	A class of morphologically heterogeneous cytoplasmic particles in animal and plant tissues characterized by their content of hydrolytic enzymes and the structure-linked latency of these enzymes. The intracellular functions of lysosomes depend on their lytic potential. The single unit membrane of the lysosome acts as a barrier between the enzymes enclosed in the lysosome and the external substrate. The activity of the enzymes contained in lysosomes is limited or nil unless the vesicle in which they are enclosed is ruptured or undergoes MEMBRANE FUSION. (From Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed).	Autolysosome,Autolysosomes,Lysosome
D011500	Protein Synthesis Inhibitors	Compounds which inhibit the synthesis of proteins. They are usually ANTI-BACTERIAL AGENTS or toxins. Mechanism of the action of inhibition includes the interruption of peptide-chain elongation, the blocking the A site of ribosomes, the misreading of the genetic code or the prevention of the attachment of oligosaccharide side chains to glycoproteins.	Protein Synthesis Antagonist,Protein Synthesis Antagonists,Protein Synthesis Inhibitor,Antagonist, Protein Synthesis,Antagonists, Protein Synthesis,Inhibitor, Protein Synthesis,Inhibitors, Protein Synthesis,Synthesis Antagonist, Protein,Synthesis Inhibitor, Protein
D011948	Receptors, Antigen, T-Cell	Molecules on the surface of T-lymphocytes that recognize and combine with antigens. The receptors are non-covalently associated with a complex of several polypeptides collectively called CD3 antigens (CD3 COMPLEX). Recognition of foreign antigen and the major histocompatibility complex is accomplished by a single heterodimeric antigen-receptor structure, composed of either alpha-beta (RECEPTORS, ANTIGEN, T-CELL, ALPHA-BETA) or gamma-delta (RECEPTORS, ANTIGEN, T-CELL, GAMMA-DELTA) chains.	Antigen Receptors, T-Cell,T-Cell Receptors,Receptors, T-Cell Antigen,T-Cell Antigen Receptor,T-Cell Receptor,Antigen Receptor, T-Cell,Antigen Receptors, T Cell,Receptor, T-Cell,Receptor, T-Cell Antigen,Receptors, T Cell Antigen,Receptors, T-Cell,T Cell Antigen Receptor,T Cell Receptor,T Cell Receptors,T-Cell Antigen Receptors
D002460	Cell Line	Established cell cultures that have the potential to propagate indefinitely.	Cell Lines,Line, Cell,Lines, Cell
D002474	Cell-Free System	A fractionated cell extract that maintains a biological function. A subcellular fraction isolated by ultracentrifugation or other separation techniques must first be isolated so that a process can be studied free from all of the complex side reactions that occur in a cell. The cell-free system is therefore widely used in cell biology. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p166)	Cellfree System,Cell Free System,Cell-Free Systems,Cellfree Systems,System, Cell-Free,System, Cellfree,Systems, Cell-Free,Systems, Cellfree
D002499	Centrifugation, Density Gradient	Separation of particles according to density by employing a gradient of varying densities. At equilibrium each particle settles in the gradient at a point equal to its density. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Centrifugations, Density Gradient,Density Gradient Centrifugation,Density Gradient Centrifugations,Gradient Centrifugation, Density,Gradient Centrifugations, Density
D004705	Endocytosis	Cellular uptake of extracellular materials within membrane-limited vacuoles or microvesicles. ENDOSOMES play a central role in endocytosis.	Endocytoses
D005455	Fluorescent Antibody Technique	Test for tissue antigen using either a direct method, by conjugation of antibody with fluorescent dye (FLUORESCENT ANTIBODY TECHNIQUE, DIRECT) or an indirect method, by formation of antigen-antibody complex which is then labeled with fluorescein-conjugated anti-immunoglobulin antibody (FLUORESCENT ANTIBODY TECHNIQUE, INDIRECT). The tissue is then examined by fluorescence microscopy.	Antinuclear Antibody Test, Fluorescent,Coon's Technique,Fluorescent Antinuclear Antibody Test,Fluorescent Protein Tracing,Immunofluorescence Technique,Coon's Technic,Fluorescent Antibody Technic,Immunofluorescence,Immunofluorescence Technic,Antibody Technic, Fluorescent,Antibody Technics, Fluorescent,Antibody Technique, Fluorescent,Antibody Techniques, Fluorescent,Coon Technic,Coon Technique,Coons Technic,Coons Technique,Fluorescent Antibody Technics,Fluorescent Antibody Techniques,Fluorescent Protein Tracings,Immunofluorescence Technics,Immunofluorescence Techniques,Protein Tracing, Fluorescent,Protein Tracings, Fluorescent,Technic, Coon's,Technic, Fluorescent Antibody,Technic, Immunofluorescence,Technics, Fluorescent Antibody,Technics, Immunofluorescence,Technique, Coon's,Technique, Fluorescent Antibody,Technique, Immunofluorescence,Techniques, Fluorescent Antibody,Techniques, Immunofluorescence,Tracing, Fluorescent Protein,Tracings, Fluorescent Protein
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man