Intracellular signaling: from simplicity to complexity.

The field of intracellular signaling is barely a half-century old (Robison et al, 1971). In that span of time, our concepts concerning the organization and function of intracellular signaling have gone from viewing such signaling events in terms of a few simple models, to viewing them in terms of highly complex models that display both spatial and temporal domains of signal action. It has become apparent that even apparently simple processes, such as the secretion of the peptide hormone, insulin, from the beta-cell involves highly complex, interacting networks of signaling molecules to which the terms synarchic regulation and crosstalk have been applied. In this brief survey of cell signaling an attempt will be made to provide a global view of our present understanding of some aspects of their complexity. In doing so, I shall start with a consideration of the basis of all signaling, and a presentation of some early simple models as a means of providing a framework for what follows.