Cell to Cell Signaling

  1. 3 major types of interactions between adjacent cells? Where are they found in?
    Gap junctions

    Functional Synctium

    Connexins: Connect & Share Cytoplasm

    Found inbetween neurons, smooth muscle cells, cardiac tissue, bone celle.
  2. Give example nd definition of contact dependent cells.
    Example: CAMs

    Bind to surface of cell membranes
  3. Name Long Distance Chemical Coupling
    What do they do?
    • Neurocrines: Chem made by neurons
    • Neurohormones: chem made by neurons made in hypothalamus

    Neuromodulators: chem made by neurons to alter 2nd messenger response.
  4. What do cytokines do?

    • cell development,
    • Cell differentiation,
    • & Immune response

    Distance: both short and long distance
  5. What are three components of cell signaling?
    • Extracellular First messengers
    • Receptors
    • Intracellular Second Messengers
  6. Types of competition:
    ex of each
    • Agonist: attaches and mimics first messenger
    • Ex: Ephederine

    • Antagonist: get in way of receptors, deactivating them.
    • Ex: Beta blockers to lower BP
  7. What happens when there is too much first messengers?
    • Down Regulation
    • Desensitization

    Receptors are still there but not the active site.
  8. What happens when there is too little first messengers?

    An increase of sensitivity of binding sites + more FM
  9. What are the Short distance local signal cells?
    Paracrines: Chem made by neurons, signal neighbor cells

    Autocrines: Chem made by themselves for itself.
  10. Receptors are
    mediator cells between FM and SM found in cell membrane or cytosol
  11. What do secondary messengers do?
    Stimulate a cell response
  12. Give some examples of what some of the first messengers are:
    • Hormones
    • Neurotransmitters
    • Neurohormones
    • Local Chemical Mediators
    •      a. paracrines
    •      b. autocrines
    •      c. Cytokines
  13. Water-Soluble or Lipophobic act on
    receptors in cell membrane.

    Lipophobic WILL NOT dissolve in lipid bilayer
  14. Lipid Soluble or Lipophillic act on
    receptors in cytoplasm or nucleoplasm of cell
  15. Define Amplification
    Amplifier enzyme activates a secondary messenger
  16. Superfamilies
  17. Define transduction
    Process by which stimulus is transformed into cell response.
  18. What is an example of
    Receptor-Operated Channels
    Ligand-Gated Ion Channels
    Nicotinic attaches in place of ACH (adrenaline)
  19. Receptor-Operated Channels
    Ligand-Gated Ion Channels
    Open/close by a receptor that attaches and acts as ion channel directly
  20. Proteins can work as:
    • Receptors
    • Ions
    • Channels
    • Enzymes

  21. Receptor-enzymes are all...
    Protein Kinases except for one guanylyl cyclase activity
  22. Recptor Tyrosine Kinases
    • Binding of messenger to receptor on cytoplasmic side of PM.
    • Tyrokinase = Activated = Insulin Receptor Attaches
    • Autophosphorylates
    • Bind and activate other proteins
    • Glut 4 activated to insert into membrane Guanylyl Cyclase funcs as receptor & Cyclic-GMP as second messenger
  23. Receptors that stimulate G proteins:
    • Alpha --> GDP & GTP
    • Betta & Gamma --> Help anchor Alpha

    • Binding of FM Occurs On receptor
    • Activated receptor = higher affinity for Alpha
    • Alpha disassociates from betta/gamma
    • Allows alpha to bind to other PM proteins
    •          (ion channel or enzyme thus called effector proteins)
    • G-protein cples recept to effector proteins
    • Activated effector GTP-ase to cleave GTP into GDP + P1

    This renders alpha subunit inactive allowing to recombine w/ its betta and gamma sub units.
  24. What makes up a G-Protein?
    • Bound to inactive receptors is a protein complex located on cytoplasmic side of Plasma membrane.
    • (alpha beta gamma)
  25. Receptors that generate cyclic-AMP as SM (pathway
  26. Signal pathways must be terminated via any one of these:
    • Remove the First Messenger(Brk dwn FM enz)
    • Inactivate Receptors(PO4/Endo/ClathPIT)
    • Removal of second messenger
    • (rmvl of F.M or break down 2nd Messenger)
  27. What had First messengers but no receptors?

  28. Examples of drugs aimed at transduction
  29. Pathway initiated by Lipid-Soluble Messengers
    • M binds 2 inactive receptors in nucleus
    • Gene Transcription
    • Diffuses out capillaries/across P.M Binds 2 rec in nucleus
    • Transcription factors
    • mRNA move out of nucleus synthesizes on ribosomes
    • Cells ultimate response
  30. Pathway initiated by Water-soluable messengers.
    • Bind 2 extracellular portion on PM
    • Secondary messenger in cytoplasm activated
    • Diffuses through PM
    • Protein Kinase
    • Cell Response
  31. What are signaling for water soluble molecules?
    Receptors/channels: ex Nicotinic receptor

    Receptor/Enz: ex: Guanacyc. Tyr. Kinase GMP

    Receptor/CAM: ex
  32. Which pathways fall under PLASMA-MEMBRANE RECEPTORS pathway category?
    • a. Receptors that themselves function as ion channels.
    • b. Receptors that themselves function as enzymes.
    • c. Receptors that are bound to and activate cytoplasmic JAK kinases.
    • d. Receptors that activate G proteins, which in turn act upon
    • effector proteins—either ion channels or enzymes—in the plasma membrane.
  33. Which pathway is associated with intracellular receptors?
    • lipid-soluble messengers)
    • Function in the nucleus as transcription
    • factors to alter the rate of transcription of particular genes.
Card Set
Cell to Cell Signaling