Introduction and Overview of Alterations in Cell Signaling

Cellular homeostasis involves the orchestration of complex biochemical events that ensure survival and preservation of differentiated functions. Toxic injury often alters cellular programming in ways that disrupt cellular signaling pathways and give way to altered states that may or may not be consistent with cellular functions. For simplicity, this chapter has been organized to cover the major components of signal transduction: the specific signals, the sensors, and their corresponding signaling pathways. How toxic chemicals impinge on each of these components will be discussed in general terms and reference to the specifics covered in other chapters provided when appropriate. The goal of this chapter is to describe the signaling pathways that are often affected by carcinogenic compounds, specifically tumor promoters. The basic framework of the signal transduction cascade will be investigated. In subsequent chapters, specific examples of xenobiotic alterations in signal transduction will be portrayed, as will the ultimate toxic responses of altered cell cycle control and apoptosis.