Introduction to Signal Transduction—Section 17.1

Cells respond to their environment through a complex and interdependent series of signal transduction pathways that frequently begin at the cell membrane. Many cellular receptors are transmembrane proteins with extracellular domains that selectively bind ligands. In response to ligand binding, the receptor's cytoplasmic domain may change conformation and transmit the signal across the membrane, or individual receptors may aggregate and interact with other membrane proteins in order to generate a response. Transmembrane signals trigger a cascade of events in the cell, which can include changes in intracellular Ca²⁺ levels, enzymatic activity and gene expression (Figure 17.1.1).

We offer several important reagents for studying signal transduction mechanisms, including Ca²⁺ regulation and second messenger activities. This chapter focuses on probes for events occurring downstream from the receptor–ligand interaction. These products complement the probes for receptors and ion channels in Probes for Endocytosis, Receptors and Ion Channels—Chapter 16, as well as the many ion indicators discussed in Indicators for Ca2+, Mg2+, Zn2+ and Other Metal Ions—Chapter 19, pH Indicators—Chapter 20 and Indicators for Na+, K+, Cl– and Miscellaneous Ions—Chapter 21. Probes for Reactive Oxygen Species, Including Nitric Oxide—Chapter 18 describes our selection of probes for nitric oxide research—including nitric oxide donors, nitric oxide synthase inhibitors and reagents for nitrite detection—as well as for other reactive oxygen species.