Second Messengers
- 1Department of Pharmacology, University of California at San Diego, La Jolla, California 92093
- 2Department of Life, Health and Chemical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom
- 3Department of Pharmacology, Howard Hughes Medical Institute, University of Washington School of Medicine, Seattle, Washington 98195
- Correspondence: anewton{at}ucsd.edu
Abstract
Second messengers are small molecules and ions that relay signals received by cell-surface receptors to effector proteins. They include a wide variety of chemical species and have diverse properties that allow them to signal within membranes (e.g., hydrophobic molecules such as lipids and lipid derivatives), within the cytosol (e.g., polar molecules such as nucleotides and ions), or between the two (e.g., gases and free radicals). Second messengers are typically present at low concentrations in resting cells and can be rapidly produced or released when cells are stimulated. The levels of second messengers are exquisitely controlled temporally and spatially, and, during signaling, enzymatic reactions or opening of ion channels ensure that they are highly amplified. These messengers then diffuse rapidly from the source and bind to target proteins to alter their properties (activity, localization, stability, etc.) to propagate signaling.
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