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Cell Signaling A.Types of Cell Signaling B.Intracellular Receptor Signaling: Steroid Hormones C.Cell Surface Receptors: Types D. Cell Surface Receptors:

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Presentation on theme: "Cell Signaling A.Types of Cell Signaling B.Intracellular Receptor Signaling: Steroid Hormones C.Cell Surface Receptors: Types D. Cell Surface Receptors:"— Presentation transcript:

1 Cell Signaling A.Types of Cell Signaling B.Intracellular Receptor Signaling: Steroid Hormones C.Cell Surface Receptors: Types D. Cell Surface Receptors: G-protein linked receptors

2 A.Types of Cell Signaling Direct cell-cell signaling vs. signaling via secretion

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4 A.Types of Cell Signaling Cell surface receptors vs. Intracellular receptors

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6 A.Types of Cell Signaling Three forms of signaling by secreted molecules –Paracrine –Synaptic –Endocrine

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9 A.Types of Cell Signaling Gap junctions

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11 A.Types of Cell Signaling The same signal can produce different effects in different cells

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13 A.Types of Cell Signaling Proper signaling generally depends on a signal molecule being degraded rapidly

14 A.Types of Cell Signaling Types of Signals based on Where they Bind –To an intracellular receptor: e.g. Steroid hormones –To a cell-surface receptor: G-protein linked, enzyme-linked, or ion channel- linked

15 B.Intracellular Receptor Signaling: Steroid Hormones Overview of Steroid Hormone Action: –Steroid hormone (small, hydrophobic) is secreted by glandular cells and released into bloodstream (usually transported via shuttle proteins) –The hormone enters the cytoplasm of cells –In the cytoplasm of target cells, the hormone binds to steroid hormone receptor protein

16 B.Intracellular Receptor Signaling: Steroid Hormones Overview of Steroid... (cont.): –The steroid-receptor conplex is translocated into the nucleus, where it activates the transcription of the primary response genes –Transcription of the primary response genes, followed by translation, results in the production of primary response proteins

17 B.Intracellular Receptor Signaling: Steroid Hormones Overview of Steroid... (cont.): –The primary response proteins usually inhibit further transcription of their own genes, and they may activate transcription of secondary response genes.

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21 C.Cell Surface Receptors: Types Three known classes of cell surface receptors –Ion channel-linked, G-protein-linked, Enzyme-linked –An activated cell-surface receptor triggers a phosphorylation cascade

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25 D. Cell Surface Receptors: G-protein linked receptors Largest family of cell surface receptors –Different ones respond to a wide variety of mediators including different hormones, neurotransmitters, local mediators –Examples: Receptors to epinephrine, acetylcholine, serotonin

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27 B.G-linked Receptors What do G-protein receptors do? –G-protein receptors activate trimeric G- protein –Activated G-protein alters the cellular concentration of a second messenger: usually cyclic AMP or Ca 2+ –The second messenger activates a protein kinase enzyme –The protein kinase phosphorylates another enzyme and alters its activity

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32 B.G-linked Receptors Trimeric G-proteins disassemble when activated –Three chains: and – chain binds and hydrolyzes GTP – & chains form a tight complex that anchors G-protein to the plasma membrane

33 B.G-linked Receptors Trimeric G-proteins disassemble when activated –Inactive G-protein has a bound GDP –When activated: GDP dissociates, new GTP is bound –This causes to dissociate from – binds to adenylate cyclase, altering its activity –G s protein stimulates activates adenylate cyclase, G i inhibits it

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36 B.G-linked Receptors Action of epinephrine on glycogen metabolism –Epinephrine (adrenaline) is released from the adrenal gland in times of stress. It has two overall actions on glycogen metabolism: it inhibits glycogen synthesis, and it promotes glycogen breakdown –This is mediated by a protein phosphorylation cascade

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