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.
- 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 cell signals. Hormones communicate signals far from their origin. An example is opiates.
- Growth Factors are a broad group of chemicals used as cell signals. 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 a receptor.
Opiates are an example of agonists; they 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.
EGF and FGF inhibitors are examples of antagonists, drugs that block growth factors from docking onto EGF and FGF receptors on various cells. Growth factors are chemical signals 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.
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