Lecture 23 12

Lecture 23 12 - Lecture 23 12/07/07 Cell Signaling and...

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Lecture 23 12/07/07 Cell Signaling and Signal Transduction Cell Signaling – How cells communicate with other cells and its environment Local and long distance signaling o Local: paracrine + autocrine singaling Paracrine – specifically when one cell secretes ligand, ligand is recognized by neighboring cell. Receptor is in close proximity but different cell types Autocrine – when cell that is secreting and recognizing are the same cell types within a tissue o Long: endocrine + synaptic Endocrine – when cell produce a signal or ligand, signal is secreted into circulatory system (blood or lymph) travel to distant location Synaptic – neurons communicate with each other electrical signal recognized by another cell neurotransmitter Signaling functions within cell by signaling pathways o When ligand binds Intracellular signal transduced inside cell Ligand = 1 st messenger 2 nd messenger activated by receptor, not directly by ligand o Example: adrenaline – ligand, 2 nd messenger – cyclic AMP capable of activating other pathways in cell G-protein Coupled Receptors (GPCR’s) – large family of cell surface receptors o 7 transmembrane domain containing proteins + 1 ligand binding domain o G-protein associated with these receptors (they are not small) o G-protein: Heterotrimeric G-proteins (3 subunits) Cause activation of signal transduction cascade α and γ subunits anchor into membrane by myristolated tail (14 C saturated fatty acid tail) Myristolated tails localize to lipid rafts and caveolae G-protein attaches near where G-protein receptor will be when receptor is not bound Ligand acts as GEF Ligand binds GDP GTP Gα separates from Gβγ Gα is more active, carry out more functions Gβγ always stick together, act as one subunit Both activate different downstream signaling events How to shut off: hydrolyze Gα GDP, Gα rebinds to Gβγ return to plasma membrane Example: How glucose is mobilized when adrenaline is produced and binds to cells in liver Ligand (1 st messenger) = Adrenaline When Adrenaline binds, cell wants to make more glucose
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Lecture 23 12 - Lecture 23 12/07/07 Cell Signaling and...

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