Vesicle-to-cell protein transfer: insertion of band 3, the erythrocyte anion transporter, into lymphoid cells

Band 3, the erythrocyte anion transporter, transfers spontaneously between human red cells and model membranes. During incubation of intact erythrocytes with sonicated dimyristoylphosphatidylcholine vesicles, the transporter inserts in functional form and native orientation into the liposome bilayer, with the cytoplasmic segment of the protein contacting the lumen of the vesicle [Newton, A. C., Cook, S. L., & Huestis, W. H. (1983) Biochemistry 22, 6110-6117; Huestis, W. H., & Newton, A. C. (1986) J. Biol. Chem. 261, 16274-16278]. When band 3-vesicle complexes are incubated with erythrocytes whose native band 3 has been inhibited irreversibly, reverse transfer of the protein restores anion transport capacity to the cells [Newton, A. C., Cook, S. L., & Huestis, W. H. (1983) Biochemistry 22, 6110-6117]. Here we report the vesicle-mediated transfer of band 3 to human peripheral blood lymphocytes and to cultured murine lymphoma cells (BL/VL3). Subsequent to incubation with protein-vesicle complexes, both lymphoid cell types exhibit a 2-4-fold increase in the rate of chloride uptake. This enhanced permeability is inhibited greater than or equal to 98% by the exofacial band 3 inhibitor 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid, consistent with right-side-out insertion of functional band 3 into the lymphoid cell membrane.     

Resistivity of Red Blood Cells Against High-Intensity, Short-Duration Electric Field Pulses Induced by Chelating Agents

The interaction of human red blood cells (RBCs) with diethylenetriamine-pentaacetic acid (DTPA) or its Gd-complex (Magnevist, a widely used clinical magnetic resonance contrast agent containing free DTPA ligands) led to the following, obviously interrelated phenomena. (i) Both compounds protected erythrocytes against electrohemolysis in isotonic solutions caused by a high-intensity DC electric field pulse. (ii) The inhibition of electrohemolysis was observed only when cells were electropulsed in low-conductivity solutions. (iii) The uptake of Gd-DTPA by electropulsed RBCs was relatively low. (iv) (Gd-) DTPA reduced markedly deformability of erythrocytes, as revealed by the electrodeformation experiments using high-frequency electric fields. Taken together, the results indicate that (Gd-) DTPA produce stiffer erythrocytes that are more resistant to electric field exposure. The observed effects of the chelating agents on the mechanical properties and the electropermeabilization of RBCs must have an origin in molecular changes of the bilayer or membrane-coupled cytoskeleton, which, in turn, appear to result from an alteration of the ionic equilibrium (e.g., Ca²⁺ sequestration) in the vicinity of the cell membrane. Received: 19 January 1999/Revised: 1 April 1999     

Functional anatomy of the musculature of the trachea.

The smooth musculature of the human trachea was studied and compared with earlier observations in the rabbit. The results may be summarized as follows: 1. The annular m. constrictor tracheae, previously observed in the rabbit, has also been identified in the human trachea. 2. Longitudinal muscle fibers outside the constrictor musculature were observed in man. These fibers are rudimentary and appear to be of no functional importance. 3. From a functional point of view, it appears justified to regard the outer tracheal musculature largely as a constrictor musculature. 4. The main function of the outer musculature of the trachea and the elastic cartilaginous arches is to maintain the stability of the tracheal wall. 5. The variation of the lumen of the trachea is mainly controlled by the m. trachealis in the pars membranacea.     

Protein degradation during the differentiation of eukaryotic cells: studies on the sporulation of Saccharomyces cerevisiae and on the formation of the neuromuscular junction in the chick embryo.

The role of protein degradation in cell and tissue differentiation has been investigated during the sporulation of Saccharomyces cerevisiae and during endplate formation in developing avian muscle. The results suggest that a variety of proteolytic processes as enzyme inactivation, degradation of mitochondrial membrane constituents and removal of embryonic cell surface proteins exert stringent controls over the sequence of differentiation in eukaryotic cells.     

Synthesis by Enzymatic Catalysis VI—An Investigation of Chemical Modification of HRP by Fourier Transform Infra-Red Vibrational Spectroscopy

Horseradish peroxidase was chemically conjugated on its carbohydrate moieties with short aliphatic chains (C₈ and C₁₆). An analytical method using FT.IR spectroscopy was developed to analyze this alteration in enzyme structure. This method is non-destructive, and can be applied directly to samples of the reaction mixture. More general applications of this technique are described and discussed.