Physiology, Cellular Receptor

Excerpt

Cellular receptors are proteins either inside a cell or on its surface that receive a signal. This is a chemical signal in normal physiology where a protein ligand binds a protein receptor. The ligand is a chemical messenger released by 1 cell to signal itself or a different cell. The binding results in a cellular effect, which manifests as any number of changes in that cell, including altering gene transcription or translation or changing cell morphology. Typically, a single ligand has a single receptor to which it can bind and cause a cellular response. There are several different types of cellular signaling, all of which depend on other ligands and cellular receptors.

The major categories of cellular signaling include:

1. Autocrine: A cell releases a signal that binds 1 of its receptors to change its functioning

2. Signal across a gap junction: Small signaling molecules move directly across neighboring attached cells

3. Paracrine: Communication between cells that are nearby

4. Endocrine: Cell signals travel through the bloodstream to target cell receptors in different parts of the body

Each type of signaling requires a ligand and a receptor. Cellular receptors can broadly be categorized into internal, cell-surface, ion channel, G-protein-coupled (GPCRs), and enzyme-linked receptors. Although most cell receptor binding is by a chemical ligand, 2 notable exceptions are pathogenic viruses that can bind host cellular receptors to infect a cell and bacterial components, which can bind receptors on immune cells to cause an immune response.