In any multicellular organism, individual cells must communicate with each other through complicated cell signaling pathways. Since many medications work by altering cell signaling pathways, it is essential to understand the language of cells.

Back to Basics

A cell receives a message when a protein on its surface (called a receptor) is activated or blocked. This action causes information to flow across the cell membrane into the cell. The result of cell signaling is the “switching on” or “switching off” of protein production, which drastically alters the function of a cell.

Tricky Terms

• Receptor is a general name given to proteins found on a cell’s surface that aid in cell communication.
• Ligand is a general name given to all molecules that bind to receptors, causing a chemical reaction.
• Hormones are a broad group of chemicals used as ligands. Hormones communicate signals far from their origin. An example is opiates.
• Growth Factors are a broad group of chemicals used as ligands. Growth factors direct cells to grow and multiply. Dysfunctional growth factors can cause cancer by allowing cells to grow out of control. Examples include EGF inhibitors and FGF inhibitors.

Why It Matters

Many drugs mimic ligands and bind to receptors. Two classes of ligands are agonists and antagonists. Agonists are drugs that activate a receptor. Antagonists, by contrast, inactivate or block a receptor.

Opioid Activation

Opiates are an example of agonists; these ligands bind to and activate receptors, specifically opioid receptors on neurons. Opiates increase dopamine signals in the brain, which blocks pain. Long-term exposure to opiates causes neurons to become less sensitive, meaning more drug is required to have the intended effect, resulting in opioid tolerance and addiction. Opiates are an example of how changes in signaling pathways can affect how cells function.

Blocking Cancer

EGF and FGF inhibitors are examples of antagonists, drugs that block growth factors from docking onto EGF and FGF receptors on cells. Growth factors are ligands that cause some cancers; blocking the signal stops the cancer. Pemigatinib is just such a medication used to treat certain types of bile duct cancer.

BIG Deal

Cell signaling is a BIG deal! It governs not only how our bodies work but how drugs work at a cellular level to make us well. In as little as 85 minutes you can perfect your understanding of receptors, ligands, agonists, antagonists and so much more. Join thousands of others and register for The Biology of Biotech, the perfect place to jumpstart your biotech journey.

The Human Body

The most common cell signaling pathway is a mouthful—the mitogen-activated protein kinase (MAPK) cascade. It is essential for transmitting signals to the cell nucleus, promoting cell division and growth.