Cell Signalling provides an introduction to signalling within and between cells—one of the most important aspects of biochemistry and cell biology. It is composed of four parts, and Part 1 provides an overview of signalling and looks at the history and techniques of cell signalling. Part 2 considers components that comprise signalling pathways. For example, this part looks at extracellular signals, such as hormones, and discusses the detection of extracellular signals. Part 3 centres on selected examples of signalling pathways and events. These include insulin and the signal transduction cascades it invokes; perception of the environment; signalling in development and for the regulation of gene expression; and life, death, and apoptosis. The last part presents some final thoughts on cell signalling and looks to the future.
Chapter
An introduction to cellular signalling
This chapter opens with an introduction to one of the most important aspects of modern biochemistry and cell biology: cell signalling. It explores various aspects of cell signalling and the main principles and components behind the signalling mechanisms. The chapter argues that cell signalling is not only important for understanding the functioning of a normal cell but is also of vital importance for understanding the growth and activity of an aberrant cell or a cell combating adverse conditions. The chapter also examines what makes a good signal. It then investigates the different ways in which cells signal to each other and defines cell-to-cell signalling. Lastly, the chapter turns to the discovery of oncogenes, genes that cause the uncontrolled growth of cells that may lead to cancerous growths, and the discovery of cytokines, which held great hopes for a cure for a variety of diseases.
Chapter
Cell signalling
This chapter explains that cells communicate with one another using chemical or electrical signals that activate complex signalling pathways. It describes the cells of animals and plants which communicate using extracellular messengers or ligands, noting that local communication occurs by secreting and receiving local-acting extracellular messengers, while long-distance signalling between cells uses hormones. It also outlines a variety of biological molecules that function as extracellular messengers or ligands, which include hormones, derivatives of vitamins A and D, growth factors and cytokines, eicosanoids, and neurotransmitters. The chapter explores the common features of receptors of signal molecules, such as binding a signalling molecule and receptor. It covers signal transduction pathways, which are one of the many ways organisms coordinate their activities.
Chapter
The pituitary gland and hypothalamus
This chapter reviews the nervous and endocrine systems. These are both concerned with communication within the body. It explains how nerves communicate through rapid, specific electrical signals, whereas the endocrine system uses hormones as chemical signals to regulate physiological processes. Nevertheless, the nervous and endocrine systems are closely linked via the control that the hypothalamus exerts over the pituitary gland. The chapter explores the hypothalamo-pituitary system and provides a brief description of the principal hormones of the anterior and posterior lobes of the pituitary gland. The actions of the individual hormones deal with their target glands through hormonal control of the thyroid and parathyroid glands.
Chapter
Cell signalling: importance, complexity and the future
This chapter recalls the mechanisms used by cells to control their activities. It introduces many recurring themes in cell signalling, showing that there is a steady state condition of signalling components. The chapter argues that the most important aspects of cell signalling are that there needs to be a change and that this change needs to be recognized to elicit a response. The chapter also looks at the uniqueness of the signals used and the specific perception of the signals. The chapter considers moonlighting proteins, drug discovery, and cell signalling manipulation. Finally, it examines the future of cell signalling research.
Chapter
Signalling in development and for the regulation of gene expression
This chapter looks at the complex world of development, starting with some mechanisms of controlling transcription factor activity and the levels of gene expression. It explains that the control of gene expression plays an important role in the control of organism development. The chapter also discusses some examples of cell signalling systems that are studied in the context of developmental biology. The chapter then shifts to a discussion of transforming growth factor β—an important group of signalling proteins. It also reviews how notch signalling allows cells to have direct cell-to-cell communication and highlights hedgehog signalling, noting that it is important for developmental signalling. Finally, the chapter explores how toll-like receptors (TLRs) are used in the immune response.
Chapter
Perception of the environment
This chapter focuses on the molecular signalling of the mammalian eye. It emphasizes that all cells must be able to perceive elements of their environment, whether that includes the presence of compounds from other parts of the same organism or cues from outside. By discussing a complex signalling mechanism, the chapter illustrates how components described in earlier sections may come together to form coherent signalling pathways. It also elaborates on other systems used by organisms to perceive their environment to highlight the importance and diversity of such systems and to show that most draw on a repertoire of components. Next, the chapter considers the presence of chemicals and the response to mechanical forces, which are relevant to animals and plants.
Book
John T. Hancock
Cell Signalling starts with a brief history and general principles of cell signalling. It then turns to an examination of signals and their perception. It also discusses modifications to proteins that control cell signalling. Next, it looks at intracellular signals. The text also covers cell development before explaining cell signalling disorders, cancers, and apoptosis. Towards the end, the text moves on to stress responses and the changing cell environment. Finally, the book looks to the future, including challenges and perspectives in cell signalling, such as how its manipulation may enable new medical treatments or increase efficiency in agriculture.
Chapter
Signals and Signal Transduction
This chapter begins by providing a brief overview of the types of external cues that direct plant growth. In general, an environmental input that initiates one or more plant responses is referred to as a signal, and the physical component that biochemically responds to that signal is designated a receptor. Receptors are either proteins or, in the case of light receptors, pigments associated with proteins. Once receptors sense their specific signal, they must transduce the signal in order to amplify the signal and trigger the cellular response. The chapter then discusses how plants employ signal transduction pathways to regulate physiological responses. It examines how individual stimulus-response cascades are often integrated with other signaling pathways, termed cross-regulation, to shape plant responses to their environment in time and space. The chapter also considers phytohormone metabolism and homeostasis, as well as hormonal signaling pathways.
Chapter
Signals and Signal Transduction
This chapter begins by providing a brief overview of the types of external cues that direct plant growth. In general, an environmental input that initiates one or more plant responses is referred to as a signal, and the physical component that biochemically responds to that signal is designated a receptor. Receptors are either proteins or, in the case of light receptors, pigments associated with proteins. Once receptors sense their specific signal, they must transduce the signal in order to amplify the signal and trigger the cellular response. The chapter then discusses how plants employ signal transduction pathways to regulate physiological responses. It examines how individual stimulus-response cascades are often integrated with other signaling pathways, termed cross-regulation, to shape plant responses to their environment in time and space. The chapter also considers phytohormone metabolism and homeostasis, as well as hormonal signaling pathways.
Chapter
Communication and Control 1
The Nervous and Endocrine Systems
This chapter covers the processes of signalling in the nervous system and the endocrine system. Cells respond to environmental changes and communicate to coordinate processes, such as growth, differentiation, metabolism, and even cell death. Thus, signalling within the body involves communication between neurons. The chapter also looks at the conduction of an action which has the potential to align the length of a neuron's axon. Signal transmission between neurons occurs most commonly through the release of a chemical neurotransmitter at the synaptic terminal. The chapter then notes the four main types of receptors of cellular signalling: ionotropic and metabotropic receptors, kinase-linked receptors, and steroid receptors.
Chapter
Communication and Control 1
The Nervous and Endocrine Systems
This chapter covers the processes of signalling in the nervous system and the endocrine system. Cells respond to environmental changes and communicate to coordinate processes, such as growth, differentiation, metabolism, and even cell death. Thus, signalling within the body involves communication between neurons. The chapter also looks at the conduction of an action which has the potential to align the length of a neuron's axon. Signal transmission between neurons occurs most commonly through the release of a chemical neurotransmitter at the synaptic terminal. The chapter then notes the four main types of receptors of cellular signalling: ionotropic and metabotropic receptors, kinase-linked receptors, and steroid receptors.
Chapter
Signals and Their Perception
This chapter looks at a variety of signalling molecules and discusses how signals are generated and perceived in the absence of a receptor. It examines different types of receptors that transmit messages into or across cells. It also describes cells that are continually bombarded by molecules and environmental factors to which they may need to respond and recognize what they are responding to. The chapter emphasizes the urgency of perception to the survival of the cell itself and to multicellular organisms as a whole. It talks about a protein known as a receptor that has a structure tailored to interact in some way with the arriving signal or signalling molecule, which is referred to as a ligand.
Chapter
Insulin and the signal transduction cascades it invokes
This chapter uses insulin signalling as an example of biological systems. As the chapter discusses, once insulin has been produced, transported, and perceived, a surprisingly diverse signalling transduction mechanism may be used to bring about the final alteration of cellular function. The chapter also highlights the importance of signalling to normal cellular function, as well as its contribution to the wellbeing of an organism. The chapter also investigates how insulin leads to a complex web of intracellular signalling that involves many components. It then explores how insulin may lead to modulation of many facets of metabolism, often through an influence on nuclear events. Lastly, the chapter reviews the dephosphorylation of various proteins involved in insulin signalling.
Chapter
Pathways are the key to signalling
This chapter highlights how signalling components are grouped together in pathways. It looks at the barriers to be crossed and distances to be travelled in situations where signalling is required. The chapter contends that the relay of the message in biological signalling usually involves many components and many mechanisms, which is illustrated by some simple examples. Clearly, there are many other examples that could have been used, but these well-characterized examples have been chosen because they illustrate pertinent points that can be used to understand more complicated pathways. Finally, the chapter considers computer modelling and a systems biology approach in terms of the complexity of pathways in the future.
Chapter
Detection of extracellular signals: the role of receptors
This chapter examines the mechanisms used by cells to perceive signals, and the immediate action taken when they do. It explains that most signals are perceived at the cell surface by a variety of protein receptors, but some signals are able to penetrate the cell and therefore must be recognized on the inside, either within the cytoplasm or in the nucleus. The chapter then explores the types of receptor, their mechanisms and actions, and how they lead to the signalling cascades inside the cell to better understand cell signalling mechanisms. The chapter also reviews the binding characteristics of receptors, as an understanding of the ability of a cell to bind to a signalling ligand will reveal the capability of a cell to respond, or not. Lastly, the chapter explicates the mechanisms of how a cell may modulate its complement of receptors. It also studies receptor sensitivity and receptor density.
Chapter
Life, death and apoptosis
This chapter gives a brief insight into some of the signalling mechanisms involved in the process of apoptosis. It explicates the process called programmed cell death (PCD), often referred to as apoptosis, which leads to the death of the cell. The processes are initiated with the recognition of extracellular signals or intracellular damage, which leads to cascades of events involving specific interactions and results in a response, in this case the death of the cell involved. The chapter highlights that it is not only the survival, adaptation, and normal functioning of the cell that are under the control of cell signalling events, but also that, ultimately, death of the cell may be brought about by cell signalling cascades. Lastly, the chapter considers the two signalling pathways leading to apoptosis—the intrinsic and extrinsic pathways—and investigates the role of caspases during apoptosis.
Chapter
Neurons
This chapter discusses the electrical basis of neuronal function and shows how this correlates to the ability of neurons to generate and propagate electrical signals. It references the neurons of squids, cockroaches, jellyfish and humans to show how the cellular mechanisms of neuronal signalling are similar in all animals. Stimulation of a neuron results in a local change in membrane potential at the site of stimulation. Depending on the nature of the stimulus, the response can be either a membrane depolarisation or hyperporalisation. The chapter also considers the range of physiological control processes and the contrasting functions of neuronal and hormonal modes of integration. It notes the passive electrical properties of neurons and the propagation of action potentials.
Chapter
Feedback and control
This chapter covers electronic signals which can be used to control a property, such as the position of a piece of equipment, the intensity of a light, or the temperature of a system. It discusses feedback as an example of the return of the measurement to the controlling device, wherein the control systems that incorporate a feedback loop can be regarded as types of servo system. It also mentions the position of an object that is set electrically by a motor or other output transducer and the feedback signal that is derived from a position-sensitive input transducer. The chapter describes an open loop situation that has no feedback, wherein the accuracy of the final response relies on the complete transfer function between initial input and ultimate output. It highlights the accuracy of the closed loop incorporating feedback which is determined by the calibration of the sensing transducer.
Chapter
Signals and Signal Transduction
This chapter provides a brief overview of the types of external cues that direct plant growth and discusses how plants employ signal transduction pathways to regulate gene expression and posttranslational responses. It highlights the surprising discovery that, in the majority of cases, plant signal transduction pathways function by inactivating, degrading, or relocating repressor proteins that modulate transcription. It also explains the requirement of signal amplification via second messengers and mechanisms for signal transmission to coordinate responses throughout the plant. The chapter demonstrates how individual stimulus-response cascades are often integrated with other signaling pathways to shape plant responses to their environment in time and space. It mentions plant signal transduction mechanisms that may be relatively rapid or extremely slow.
