- Cells specifically respond to a multiplicity of signals from their environment via signal transduction cassettes, which comprise specific cell-surface membrane receptors, effector signaling systems (e.g. adenylyl cyclase, phospholipases, or ion channels) and regulatory proteins (e.g. G-proteins or tyrosine kinases).
- These signal transduction cassettes serve to detect, amplify and integrate diverse external signals to generate the appropriate cellular response.
- The variety of families of cell-surface receptors sense and transduce their specific hormone signal by transmembrane coupling to different effector systems to generate low-molecular-weight molecules, termed second messengers, such as cAMP, IP3, DAG, and Ca2+, which mediate their signaling functions by activating key protein kinases.
- The specificity of a particular hormone response can be further heightened by the variety of available phospholipase-signaling activities (PLC, PLD and PLA2). Taking into account their range of potential lipid substrates (e.g. PIP2, phosphatidylcholine, and phosphatidylethanolamine) and products (e.g. DAG, phosphatidic acid and arachidonic acid), the phospholipases can generate a diverse array of lipid second messengers to influence differentially the activity of the key protein kinases. Because, for example, many of the members of the PKC family appear to have distinct substrate repertoire of downstream signal transducers, differential activation of particular PKC isoforms can ultimately determine the specific type of biological response obtained.
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- How are appropriate cellular responses triggered by specific hormones?
- How do second messengers propagate intracellular signals?
- How do NSAIDs such as aspirin
 and ibuprofen work? |
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