Is the process by which cells absorb material (molecules such as proteins) from outside the cell by engulfing it with their cell membrane.
Also called receptor-mediated endocytosis. The import of substances (e.g., hormones, viruses, and toxins) into a cell via specific receptor/ligand binding. The entity under consideration binds to a receptor( s) located in the plasma (cell) membrane, which then invaginates (infolds) hence taking up the entity via “endosomes” (formed by pinchingoffof infold to form a “bag”) into vesicles located within the cell. It is one route to deliver essential metabolites to cells (e.g., low-density lipoprotein), and it is a means to modulate the cell’s responses to many protein hormones and growth factors (e.g., insulin, epidermal growth factor, and nerve growth factor). It is a route by which certain proteins targeted for destruction can be taken up and delivered to the cell’s lysosomes. For example, phagocytic cells have receptors enabling them to take up antigen-antibody complexes for subsequent destruction by the phagocytic cell. This route is also a means exploited by certain viruses and toxins to gain entry into cells through the otherwise impervious cell membranes (e.g., the AIDS virus and the Semliki Forest Virus). Disorders of endocytosis can lead to disease states (e.g., high cholesterol levels in the blood of people whose low-density lipoprotein receptors are impaired). Drugs (e.g., certain painkillers) can be targeted to specific receptors via receptor mapping (RM) and receptor fitting (RF) for greater efficacy.
The process of forming a vesicle within the secreting cell of material the cell will release upon appropriate signaling. The process is linked to the exocytotic process.
A method of ingestion of a foreign substance by a cell. The cell membrane invaginates to form a space for the material and then the opening closes to trap the material inside the cell.