Transmembrane interactions and the mechanisms of transport of proteins across membranes
- 1 January 1978
- journal article
- review article
- Published by Wiley in Journal of Supramolecular Structure
- Vol. 9 (3), 373-389
- https://doi.org/10.1002/jss.400090308
Abstract
We have made observations, by double fluorescence staining of the same cell, of the distributions of surface receptors, and of intracellular actin and myosin, on cultured normal fibroblasts and other flat cells, and on lymphocytes and other rounded cells. The binding of multivalent ligands (a lectin or specific antibodies) to a cell surface receptor on flat cells clusters the cell receptors into small patches, which line up directly over the actin‐ and myosin‐containing stress fibers inside the cell. Similar ligands binding to rounded cells can cause their surface receptors to be collected into caps on the surface, and these caps are invariably found to be associated with concentrations of actin and myosin under the capped membrane. Although these ligand‐induced surface phenomena appear to be different on flat and rounded cells, we propose that in both cases clusters of receptors become linked across the membrane to actin‐ and myosin‐containing structures. In flat cells these structures are very long stress fibers; therefore, when clusters of receptors become linked to these fibers, the clusters are immobilized. In round cells, membrane‐associated actin‐ and myosin‐containing structures are apparently much less extensive than in flat cells; therefore, clusters of receptors linked to these structures are still mobile in the plane of the membrane. We suggest that in this case the clusters are then actively collected into a cap by an analogue of the muscle sliding filament mechanism. To explain the transmembrane linkage, we propose that actin is associated with the plasma membrane as a peripheral protein which is directly or indirectly bound to an integral protein (or proteins) X of the membrane. Individual molecules of any receptor are not bound to X, but after they are specifically clustered into patches, a patch of receptors then becomes bound to S and hence to actin/myosin. Patching and capping of specific receptors on rounded cells is often accompanied by a specific endocytosis of the ligand‐receptor complexes. This represents one common transport mechanism of a protein (the ligand) across the plasma membrane. The possibility is discussed that this type of endocytosis is mediated by a transmembrane linkage of the clustered receptor to actin/myosin. Another mechanism of endocytosis involves the “coated pit” structures that are observed by electron microscopy of plasma membranes. The possible relationships between an actin/myosin and a coated pit mechanism of endocytosis are explored.Keywords
This publication has 46 references indexed in Scilit:
- TRANSMEMBRANE LINKAGE OF FIBRONECTIN TO INTRACELLULAR ACTIN‐CONTAINING FILAMENTS IN CULTURED HUMAN FIBROBLASTS*Annals of the New York Academy of Sciences, 1978
- The capping of lymphocytes and other cells, studied by an improved method for immunofluorescence staining of frozen sectionsJournal of Cellular Physiology, 1978
- Role of the coated endocytic vesicle in the uptake of receptor-bound low density lipoprotein in human fibroblastsCell, 1977
- The brush-border intestinal aminopeptidase, a transmembrane protein as probed by macromolecular photolabellingJournal of Molecular Biology, 1976
- Cell surface proteins and malignant transformationBiochimica et Biophysica Acta (BBA) - Reviews on Cancer, 1976
- Receptor-Mediated Control of Cholesterol MetabolismScience, 1976
- DISTRIBUTION OF FIBROBLAST SURFACE ANTIGENThe Journal of Experimental Medicine, 1974
- Mobility of carbohydrate containing sites on the surface membrane in relation to the control of cell growthFEBS Letters, 1973
- A TECHNIQUE FOR ULTRACRYOTOMY OF CELL SUSPENSIONS AND TISSUESThe Journal of cell biology, 1973
- Fluidity of the Plasma Membrane and its Implications for Cell MovementPublished by Wiley ,1973