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Cell signaling

Cell signaling. Prof.Dr .Gönül Kanıgür. Cell Signaling. All cells receive and respond to signals from their surroundings Signaling molecules that are secreted on the surface of one cell and bind to receptors expressed by the other cells

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Cell signaling

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  1. Cellsignaling Prof.Dr.Gönül Kanıgür

  2. Cell Signaling • All cells receive and respond to signals from their surroundings • Signaling molecules that are secreted on the surface of one cell and bind to receptors expressed by the other cells • The binding of most signaling molecules to their receptors initiates a series of intracellular reactions that regulate of the cell behaviour including metabolism,movement,proliferation and differentiation

  3. The ligand is the signaling molecule. • It may be a hormone,a growth factor/cytokine ,a steroid,a polypeptide,or other type of molecule.It has no activity of its own,but must bind to a macromolecule • Which is known as a receptor • Receptor when activated by ligand ,the receptor causes a change in the target cell in which it is expressed

  4. Signaling molecules • Signaling molecules, which are released by signal-producing cells, reach and transfer biological signals to their target cells to initiate specific cellular responses.

  5. signaling molecules • Extracellular molecules • Intracellular molecules

  6. 1. Extracellular molecules protein & peptides: Hormone, cytokine AA & its derivatives: Gly, Glu, adrenaline, thyroxine Steroid: Sex Hormone, glucocorticosteroid Fatty acid derivatives: prostaglandin

  7. 2.Intracellular molecule • Ca2+ ions • DG, ceramide lipid derivatives • IP3 carbohydrate derivatives • cAMP cGMP nucleotides • Ras, JAK, Raf proteins

  8. Proteins and peptides: Hormones, cytokines Effect by membrane receptors Amino acid derivatives: Catecholamines Fatty acid derivatives: Extracellular molecules Prostaglandins Effect by intracellular receptors Signal molecules Steroid hormones, Thyroxine, VD3 Intracellular molecules cAMP, cGMP, IP3, DG, Ca2+

  9. Cell Cell signaling Most signaling molecules are secreted by one cell and bind to cell surface receptorsexpressed by a target cell. The steroid hormones are small hydrophobic molecules that diffuse across the plasma membrane of their target cells and bind to intracellular receptors.

  10. Signaling molecule Receptor of target cell Signal transduction Intracellular molecule biological effect

  11. Cell Cell signaling is divided into three general categories • Endocrine • Paracrine • Autochrine • signaling based on the distance over which signals are transmitted

  12. (1) Endocrine signal • Secreted by endocrine cells. • Reach target cells by blood circulation. • Time of action is long. • Such as insulin, thyroxine, adrenalin

  13. (2) Paracrine signaling (local chemical mediators) • Secreted by common cells. • Reach neighboring target cells by passive diffusion. • Time of action is short.

  14. (3) Synaptic signal (neurotransmitters) • Secreted by neuronal cells. • Reach another neuron by synaptic gap. • Time of action is short. • Such as Acetylcholine (Ach), noradrenaline

  15. (4) Gaseous signal • Simple structure, half life is short and active in chemistry . • Such as NO, CO. • NO is amajor paracrine signaling molecule in the nervous,immune and circulary system • .NO is synthesized from the aa arginine by the enzyme nitric oxide synthase.

  16. (5) Autocrine signal • Act back to their own cells. • Such as GF, cytokine, interferon, interleukin.

  17. Direct cell to cell signaling,some signaling molecules remain bound to the cell surface and act as a ligands.these kinds off signaling take place during embryonic development

  18. Receptor Receptors are specific membrane or intracellular proteins, which are able to recognize and bind to corresponding ligand molecules, Receptor when activated by ligand ,the receptor causes a change in the target cell in which lt is expressed. Glycoprotein or Lipoprotein

  19. Function of receptor (1) Recognize the special ligand (2) Binding to special ligand (3) Signal transduction biological effect

  20. ligand A small molecule that binds specifically to a larger one; for example, a hormone is the ligand for its specific protein receptor.

  21. Membrane receptors membrane Glycoprotein • Intracellular receptors Cytosol or nuclei DNA binding protein

  22. Properties of binding of Hormoneand Receptor • highly specificity • highly affinity • saturation • reversible binding • special function model

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