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Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. 4th edition. New York: Garland Science; 2002.

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Molecular Biology of the Cell. 4th edition.

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Chapter 15Cell Communication

A trimeric GTP-binding protein, or G protein.

Figure

A trimeric GTP-binding protein, or G protein. This type of G protein functionally couples transmembrane receptors to either enzymes or ion channels in the plasma membrane. (Based on D.G. Lombright et al., Nature 379:311–319, 1996.)

According to the fossil record, sophisticated unicellular organisms resembling present-day bacteria were present on Earth for about 2.5 billion years before the first multicellular organisms appeared. One reason why multicellularity was so slow to evolve may have been related to the difficulty of developing the elaborate cell communication mechanisms that a multicellular organism needs. Its cells have to be able to communicate with one another in complex ways if they are to be able to govern their own behavior for the benefit of the organism as a whole.

These communication mechanisms depend heavily on extracellular signal molecules, which are produced by cells to signal to their neighbors or to cells further away. They also depend on elaborate systems of proteins that each cell contains to enable it to respond to a particular subset of these signals in a cell-specific way. These proteins include cell-surface receptor proteins, which bind the signal molecule, plus a variety of intracellular signaling proteins that distribute the signal to appropriate parts of the cell. Among the intracellular signaling proteins are kinases, phosphatases, GTP-binding proteins, and many other proteins with which they interact. At the end of each intracellular signaling pathway are target proteins, which are altered when the pathway is active and change the behavior of the cell. Depending on the signal's effect, these target proteins can be gene regulatory proteins, ion channels, components of a metabolic pathway, parts of the cytoskeleton, and so on (Figure 15-1).

Figure 15-1. A simple intracellular signaling pathway activated by an extracellular signal molecule.

Figure 15-1

A simple intracellular signaling pathway activated by an extracellular signal molecule. The signal molecule binds to a receptor protein (which is usually embedded in the plasma membrane), thereby activating an intracellular signaling pathway that is mediated (more...)

We begin this chapter by discussing the general principles of cell communication. We then consider, in turn, each of the main families of cell-surface receptor proteins and the intracellular signaling pathways they activate. The main focus of the chapter is on animal cells, but we end by considering the special features of cell communication in plants.

Contents

General Principles of Cell Communication

Signaling through G-Protein-Linked Cell-Surface Receptors

Signaling through Enzyme-Linked Cell-Surface Receptors

Signaling Pathways That Depend on Regulated Proteolysis

Signaling in Plants

References

By agreement with the publisher, this book is accessible by the search feature, but cannot be browsed.

Copyright © 2002, Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter; Copyright © 1983, 1989, 1994, Bruce Alberts, Dennis Bray, Julian Lewis, Martin Raff, Keith Roberts, and James D. Watson .
Bookshelf ID: NBK21059

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