Functional Role of Muscarinic Acetylcholine Receptor Subtype Diversity

Multicellular organisms use many of the same basic mechanisms as do unicellular organisms to convey information from their environment to the interior of the cell. It is reasonable to believe that although greater numbers of cellular signal transduction mechanisms are used by multicellular organisms, these mechanisms will have often evolved as a result of the duplication and divergence of genes encoding relatively few types of signal transduction molecules. Indeed, molecular cloning efforts have consistently revealed that the components of the signal transduction machinery (receptors, pumps, channels, G proteins, effector enzymes, etc.) are members of families of structurally related proteins. By using many variations on a relatively small number of signal transduction themes, multicellular organisms can fine-tune the specificity of a response for a given cell or tissue or at a particular time during development.