MCB110-Spring 2008-Nogales Signaling 49

Cell signaling is the process by which cells communicate with each other. It is essential for the survival of every cell and for the proper functioning of the organism as a whole. Cell signaling involves a series of steps, starting with the detection of a signal molecule by a receptor on the cell surface. The receptor then transmits the signal to the cytoplasm, where it activates a cascade of proteins that ultimately leads to a change in the cell’s behavior.

• What are the different types of cell signaling?
• What are the different types of receptors?
• What are the different steps involved in cell signaling?
• How does cell signaling regulate cell behavior?

Here are the answers to the questions:

• There are two main types of cell signaling: direct and indirect. Direct signaling involves the direct binding of a signal molecule to a receptor on the cell surface. Indirect signaling involves the binding of a signal molecule to a receptor on the cell surface, which then activates a second messenger that travels to the cytoplasm and activates a cascade of proteins.
• There are three main types of receptors: ion channels, G protein-coupled receptors, and receptor tyrosine kinases. Ion channels open or close in response to the binding of a signal molecule, allowing ions to flow into or out of the cell. G protein-coupled receptors activate G proteins, which then activate a cascade of proteins. Receptor tyrosine kinases phosphorylate other proteins, which then activate a cascade of proteins.
• The steps involved in cell signaling are:
  * Detection of the signal molecule by a receptor on the cell surface.
  * Transmission of the signal to the cytoplasm.
  * Activation of a cascade of proteins.
  * A change in the cell’s behavior.
• Cell signaling regulates cell behavior by controlling the expression of genes, the activity of enzymes, and the transport of molecules into and out of the cell.