From the Guidelines
A second messenger molecule, such as cyclic adenosine monophosphate (cAMP), plays a crucial role in relaying signals from receptors on the cell surface to target molecules within the cell, as seen in the context of adenosine interacting with purinergic subclass A2 receptors to increase cytosolic cAMP for vasorelaxation 1.
Definition and Function
A second messenger molecule is a chemical substance inside cells that relays signals from receptors on the cell surface to target molecules within the cell. When a first messenger (like a hormone or neurotransmitter) binds to a receptor on the cell membrane, it triggers the production or release of second messengers, which then amplify and propagate the signal throughout the cell.
Examples of Second Messenger Molecules
Common examples of second messenger molecules include:
- cyclic AMP (cAMP)
- calcium ions
- inositol trisphosphate (IP3)
- diacylglycerol (DAG) These molecules activate enzymes, open ion channels, or trigger other biochemical reactions that ultimately produce the cell's response to the original signal, as observed with adenosine increasing cytosolic cAMP for vasorelaxation 1.
Importance in Physiological Processes
The second messenger system allows a small number of extracellular signal molecules to produce a significant intracellular response, making cellular communication more efficient. This mechanism is crucial for many physiological processes, including:
- hormone action
- neurotransmission
- sensory perception enabling cells to respond appropriately to their environment, such as the regulation of coronary blood flow during stress and ischemia through adenosine 1.
From the Research
Definition of Second Messenger Molecules
- Second messengers are small molecules and ions that relay signals received by cell-surface receptors to effector proteins 2
- They include a wide variety of chemical species, such as hydrophobic molecules (e.g., lipids and lipid derivatives), polar molecules (e.g., nucleotides and ions), gases, and free radicals 2
- Second messengers are typically present at low concentrations in resting cells and can be rapidly produced or released when cells are stimulated 2
Examples of Second Messenger Molecules
- Cyclic adenosine monophosphate (cAMP) is an example of a second messenger molecule that plays a crucial role in various cellular processes, including immune function and cardiac arrhythmias 3, 4, 5
- Inositol trisphosphate (IP3) is another example of a second messenger molecule that mediates intracellular calcium mobilization and is involved in various cellular processes, including hormone action and cardiac arrhythmias 4, 6
- Diacylglycerol (DG) is a lipophilic molecule that activates protein kinase C and is involved in various cellular processes, including hormone action and cardiac arrhythmias 6
Mechanisms of Second Messenger Molecules
- Second messengers can diffuse rapidly from the source and bind to target proteins to alter their properties (activity, localization, stability, etc.) and propagate signaling 2
- The levels of second messengers are exquisitely controlled temporally and spatially, and enzymatic reactions or opening of ion channels ensure that they are highly amplified 2
- Second messengers can interact with various cellular components, including ion channels, enzymes, and receptors, to modulate cellular processes 3, 4, 6, 5