mbbs ims msu


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mbbs ims msu

  1. 1. <ul><li>Binding of the messenger to specific target cell proteins known as receptors </li></ul><ul><li>Cell response to that messenger </li></ul>Cell Communication
  2. 2. <ul><li>Receptors are proteins located either in the cell membrane or inside the cell (nucleus) </li></ul><ul><li>The messenger bind to the extracellular portions </li></ul><ul><li>Receptors are specific </li></ul>Cell Communication
  3. 3. Receptor locations <ul><li>Cytosolic or Nuclear </li></ul><ul><ul><li>Lipophilic ligand enters cell </li></ul></ul><ul><ul><li>Often activates gene </li></ul></ul><ul><li>Cell membrane </li></ul><ul><ul><li>Lipophobic ligand can't enter cell </li></ul></ul><ul><ul><li>Outer surface receptor </li></ul></ul>
  4. 4. Modulation of Signal Pathways by Ligands
  5. 5. Regulation of Receptors <ul><li>Down regulation: when a high extracellular concentration of a messenger is maintained for some time, the total number of the target cells receptors may decreased </li></ul><ul><li>Up regulation: cells exposed to low concentration of a messenger, develop sensitivity to it </li></ul>
  6. 6. Signal Transduction Pathways
  7. 7. Basic Mechanisms of Chemical Signaling
  8. 8. Pathways initiated by intracellular receptor
  9. 9. Membrane Receptor Classes <ul><li>Plasma membrane receptor (lipid insoluble) </li></ul><ul><li>Receptors function as ion channel </li></ul><ul><li>Receptor function as enzyme </li></ul><ul><li>Receptors that bound to and activate cytoplasmic JAK </li></ul><ul><li>Receptors activate G protein </li></ul>
  10. 10. General terms <ul><li>First messengers: Messengers bind to specific receptor. </li></ul><ul><li>Second messengers: non-protein substances enter the cytoplasm and diffuse throughout the cell and transmit signals </li></ul><ul><li>Protein kinase: any enzymes that phosphorylates other proteins by transferring phosphate group </li></ul>
  11. 11. Receptor function as ion channels Protein receptor constitute of ion channel Activation of the receptor by the first messenger The opening results increase diffusion of ions to the channel
  12. 12. Receptor functions as enzyme <ul><li>Receptors that posses intrinsic enzyme activity are all protein kinases </li></ul><ul><li>Binding of specific messenger to the receptor changes conformation </li></ul><ul><li>Enzymatic portion in cytoplasm is activated </li></ul><ul><li>The receptor phosphorylates its own tyrosine group </li></ul><ul><li>The phosphotyrosine bind other protein which leads signaling pathways within the cell </li></ul>
  13. 13. <ul><li>The enzymatic activity reside not in the receptor but in the separate cytoplasmic kinases </li></ul><ul><li>The binding of the first messenger to the receptor causes conformational changes that leads to activation of the JAK kinase </li></ul><ul><li>The results of these pathways is the synthesis of new proteins which mediate the cells response to the messenger </li></ul>Receptor interact with cytoplasmic JAK Kinases
  14. 14. Receptors that interact with G protein <ul><li>G Protein is a protein bound to the receptor located on the inner cytosolic surface of the plasma membrane </li></ul>
  15. 15. Receptors that interact with G proteins <ul><li>Activation of the receptor by binding of the first messenger </li></ul><ul><li>G protein activated </li></ul><ul><li>G protein stimulate effector protein adenylate cyclase </li></ul><ul><li>Conversion to cAMP </li></ul><ul><li>cAMP act as second messenger </li></ul><ul><li>Cell response to the first messenger </li></ul>