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15Mechanisms of Intracellular Signal Transduction

Receptors, which are a type of protein, serve as the doorway to intracellular signal transduction. Signals are transmitted into cells only after signal molecules bind with these receptors. Hormones and growth factors are forms of signal molecules that bind to a specific receptor and cause a specific reaction during intercellular signal transduction. Intercellular signal transduction via receptors is a very important mechanism in homeostasis.

There are various types of receptors, each mediating a unique signaling pathway. Major types are enzyme-linked, G protein-coupled, and ion-channel-linked receptors, as well as transcription factor receptors. Intracellular signal-transduction mechanisms, in which information is transduced by protein phosphorylation, G proteins, etc., can be observed in downstream signaling pathways of the receptors.

This chapter also discusses cancer as a phenomenon triggered by abnormal signal transduction. Cancer is the state in which cells proliferate in an uncontrolled and deregulated manner. The malignant alteration of cells is closely related to cell cycle and proliferation, and such mechanisms are meanwhile regulated via signal transduction. Oncogenes and tumor suppressor genes are genes encoding proteins that regulate cell proliferation. Abnormalities in such genes disrupt normal signal transduction, which eventually induces the malignant alteration of cells.

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