Question

Let's say there is a group of five receptors (A1,A2,A3,A4,A5) that are expressed in various types of tissues on the human body. But the A1 receptor, is the only family expressed in 1 type of cell. How does the A1 receptor but not the other A receptors are expressed on the cell?

Answer 1

Regardless of the nature of the signal, the target cell responds by means of a specific protein called a receptor, which specifically binds the signal molecule and then initiates a response in the target cell. In most cases, these receptors are transmembrane proteins on the target cell surface. When they bind an extracellular signal molecule (a ligand), they become activated and generate a cascade of intracellular signals that alter the behavior of the cell. In other cases, the receptors are inside the target cell, and the signal molecule has to enter the cell to activate them..

A typical cell in a multicellular organism is exposed to hundreds of different signals in its environment. These signals can be soluble, bound to the extracellular matrix, or bound to the surface of a neighboring cell, and they can act in many millions of combinations. The cell must respond to this babel of signals selectively, according to its own specific character, which it has acquired through progressive cell specialization in the course of development.

Many signaling pathways cause a cellular response that involves a change in gene expression. Gene expression is the process in which information from a gene is used by the cell to produce a functional product, typically a protein. It involves two major steps, transcription and translation.

Signaling pathways can target either or both steps to alter the amount of a particular protein produced in a cell.

Each cell type displays a set of receptors that enables it to respond to a corresponding set of signal molecules.These signal molecules work in combinations to regulate the behavior of the cell. If deprived of appropriate survival signals, a cell will undergo a form of cell suicide known as programmed cell death, or apoptosis.