8-_Cell_signaling

8-_Cell_signaling - Cell Signaling and Signal Transduction...

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1 Cell Signaling and Signal Transduction Communication between cells
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2 Need for cell-cell communications • In multicellular organisms, most cells are specialized to carry out specific functions. • Many biological processes require various cell types to work together and to coordinate their activities • Cells have to communicate with each other Cell signaling Cell signaling is the process that make it possible for cells to talk to each other and for an organism to function as a coherent system. • All cells are able and need able and need to sense sense and respond respond to specific aspects of their environment
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3 Importance of cell signaling • Cell signaling affects virtually every aspect of cell structure and function • Cell signaling is intimately involved in the – Cellular metabolism and homeostasis – regulation of cell growth and division --- cancer research – Regulation of cell differentiation and specification --- cell fate and tissue/organ formation
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4 The basic elements of cell signaling • Cell can release chemical signals that are recognized by another cell, either nearby or at a distant location. • Inter-cellular communication involves interactions between regulatory regulatory chemical messengers chemical messengers ( extracellular ), – and the specific specific receptors receptors located on the surfaces of cells • Cells also communicate with one other – By displaying molecules on their surfaces that are recognized by receptors on the surface of other cells – Requiring cells to come into direct physical contact.
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5 Different types of chemical signals can be received by cells • Water-soluble messengers --- hydrophilic – amino acids, peptides, proteins, nucleosides or nucleotides. – Function lies entirely in their ability to bind one or more specific receptors on a target cell – e.g. glutamate, glycine, acetylcholine, epinephrine, dopamine – e.g. growth factors and hormones • Lipid-soluble messengers --- hydrophobic – Act on receptors in the nucleus or cytosol (intracellular receptors) to regulate gene transcription. – e.g. steroid hormones (structurally similar to cholesterol) and retinoids (derived from Vit. A)
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6 Signaling molecules are often classified based on the distance between their site of production and the target tissue(s) upon which they act. May be local or distant Endocrine signals Endocrine signals – They are produced at great distances from their target tissues, and carried by the circulatory system to various sites in the body. – Hormones Paracrine Paracrine signals signals – Released locally, where they diffuse to act at short range on nearby tissues Autocrine Autocrine signals signals – Local mediators act on the same cell that produces them
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7 Receptors for sensing the signals • Cells can only respond to an extracellular message if they express receptors that specifically recognize and bind that particular messenger molecule (ligand) • Once a messenger reaches its target tissue, it
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8-_Cell_signaling - Cell Signaling and Signal Transduction...

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