Cell Biology Lecture CB10: Cell Communication Systems PDF

Cell Biology Theme 2: Cell signalling and regulation Lecture CB10 Cell communication systems Dr Alessandra da Silva Dantas [email protected]  CB10 Cell communication systems (Part 1) Aims 1. To outline cell communicati...

Cell Biology Theme 2: Cell signalling and regulation Lecture CB10 Cell communication systems Dr Alessandra da Silva Dantas [email protected]  CB10 Cell communication systems (Part 1) Aims 1. To outline cell communication systems 2. To describe the range of signalling molecules 3. To discuss mechanisms of action of signalling molecules  Why do cells communicate? To develop (defining position, function, fate, growth) To function (an organism is a a community of cells) E.g. the physiological function of a tissue is co-ordinated via signals from different cell types that make that tissue To sense and respond to the environment (nutrients, infections, light etc.) The means by which cells communicate is called signalling (transmission and interpretation of complex signals)  A cell signalling flow chart Extracellular signals Selective signal reception by target cell (interaction with a specific receptor) Signal transduction (conversion of signal from one form to another) Intracellular signalling molecules Epidermal growth factor receptor (EGFR) activation Molecular change e.g. gene transcription/protein function Alteration in cell behaviour https://doi.org/10.3390/ijms141020597  Range of signalling molecules Proteins e.g. glucagon Peptides e.g. vasopressin and neuropeptide Amino acid derivatives e.g. adrenaline Nucleotides e.g. ATP Steroids e.g. oestradiol Lipid derivatives e.g. prostaglandins Mechanisms of action of signalling molecules Endocrine signalling Hormones are the signalling molecules Produced in specific tissues (endocrine organs) Very ‘public’ – acts systemically (whole body) via the blood stream amino acid derivatives, peptide and protein hormones act via receptors on the plasma membrane to regulate metabolism steroid hormones act via intracellular receptors to regulate metabolism The specific receptors are selectively expressed by the target cells  Mechanisms of action of signalling molecules Endocrine signalling Involved in response to nutritional changes, changes in physical states (e.g. exercise) Involved in fundamental changes during development (thyroid and steroid hormones) Induce wide-ranging metabolic changes Regulate physiological processes Link: Metabolism and Homeostasis course Mechanisms of action of signalling molecules Paracrine signalling Cytokines and growth factors are the signalling molecules Local process involving diffusion through the extracellular medium Act via receptors on the plasma membrane Regulate local processes: Involved in development and wound healing (e.g. transforming growth factor, TGF) Involved in inflammation (e.g. Interleukin-1, IL-1) Link: CB15 Cell and tissue differentiation Mechanisms of action of signalling molecules Neuronal signalling Delivered over long distances but not broadcast Transmitted quickly and specifically to target cells (via axons) Electrical signal via axons trigger extracellular chemical signals (neurotransmitters) Neurotransmitters (e.g.acetylcholine) relay signal across synapse Link: Physiology and Neurobiology course Mechanisms of action of signalling molecules Contact dependent signalling Membrane or matrix bound molecules are the signalling molecules Bind to a receptor on target cell membrane Direct physical contact Important in development and immune responses  CB10 Cell communication systems (Part 1) Summary 1. Biological principles of communication systems 2. The diversity of signalling molecules with examples 3. The general mechanisms of action of signalling molecules with examples  CB10 Cell communication systems (Part 2) Aims 1. To outline the role of receptors in signalling 2. To explain the different cell responses to signalling  The role of receptors in signalling General features of cell signalling Cells respond selectively to signals This is determined by what receptors are expressed by that cell type (which is determined by cell history and current state) Cell behaviour is determined by the response to signals: different cells respond to the same signal in different ways The response is determined by the signalling pathways as much as the nature of the signal itself  The role of receptors in signalling – an example Acetylcholine induces different responses in different target cells via the same receptor and uses a different receptor on skeletal muscle cells (which signals via different intracellular signalling pathways) The response is determined not just by the signal molecule itself but by the nature of the receptor and the intracellular signaling mechanisms  Different cell responses to signalling Integration of signals: individual signals do not act independently of one another: the presence of one signal can modify responses to another signal Link: CB15 Cell and tissue differentiation; CB16 Cell division; CB17 Cell death How different cellular responses to signalling occur? Rapid responses: change the activity of proteins already present in the cell e.g. muscle contraction Slower responses: require changes in gene expression and protein synthesis e.g. cell division How different cellular responses to signalling occur? Large, hydrophilic molecules bind to cell surface receptors and activate intracellular signalling molecules (leading to both rapid and slower responses) e.g. insulin, glucagon, acetylcholine, cytokines Small, hydrophobic (often flat) molecules pass through the cell membrane and bind to cytoplasmic or nuclear receptors and regulate gene transcription e.g. cortisol  CB10 Cell communication systems (Part 2) Summary 1. Receptor expression, specificity and response 2. Different cell responses to signalling: integration of signalling, temporal aspects, extracellular and intracellular receptors