Lecture 19 Signaling Pathways (Receptors, Second Messengers, and Intracellular Signal Transduction)

Lecture 19 Signaling Pathways (Receptors, Second Messengers, and Intracellular Signal Transduction)

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IPHY 3060 Lecture 21: Signaling Pathways I: Receptors, Second Messengers, and Intracellular Signal Transduction
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Cells don’t live in a vacuum—they communicate with each other Cells in multicellular organisms have to communicate with each other to regulate many cellular functions
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3 Kinds of Cell-Cell Signaling in Multicellular Organisms Gap junction signaling —direct cell-to-cell communication produced by membrane pore complexes between adjacent cells Cell surface signaling proteins on surface of adjacent cells bind together Secreted factor signaling —cells secrete factors that bind to receptors on other cells
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Gap Junctions Connexins transmembrane proteins that form gap junctions Connexins form connexon hemichannels on one cell that lines up with a hemichannel on another cell to form a pore
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Example of Gap Junction Signaling-- Cardiomyocytes Need to contract at almost exactly the same time in order to pump blood efficiently Gap junctions allow ions to flow through cells, initiating action potential in adjacent cells without the need for neurotransmitter communication
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Cell surface signaling Immune system and antigen recognition Development
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Secreted Factor Signaling
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4 Types of Secreted Factor Signaling Hormonal —long range— specialized cells secrete factors (hormones) into the blood stream where they eventually are delivered to distal target cells Paracrine —short range— nonspecialized cells secrete factors that act on target cells nearby Synaptic —short range—special type of paracrine signaling in which a neuron communicates with another neuron Autocrine —very short range— nonspecialized cell secretes factors that act on itself
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Paracrine/Autocrine Signaling Secreted factors often affect nearby cells and the secreting cell All cells engage in paracrine/autocrine signaling Regulates critical day-to- day processes such as proliferation, differentiation, migration, survival
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2 Main Classes of Secreted Factors Hydrophilic --charged peptide chains which can’t cross membrane and that bind to cell surface receptors Lipophilic --steroid and other molecules which can cross cell membrane and bind to cytosolic receptors
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Key Point: Both hydrophilic factors and lipophilic factors can be either hormones OR autocrine/paracrine factors
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Key Point: Lipophilic factors bind to intracellular receptors and change gene expression
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Lipophilic factors Bind to intracellular receptor Intracellular receptor is actually a transcription
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This note was uploaded on 08/11/2010 for the course IPHY 3060 taught by Professor Allen,davi during the Fall '09 term at Colorado.

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Lecture 19 Signaling Pathways (Receptors, Second Messengers, and Intracellular Signal Transduction)

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