Intercellular Communication - Ligands and Receptors

1. Selective recognition of the arriving signal via a receptor/signal complex

2. A means of amplification by producing soluble, intracellular messengers and reversible protein phosphorylation for signal transduction

3. Appropriate nature and duration of response

4. Graded nature of response: more stimuli → greater response

5. Mechanisms of control: feedback (+/-) and desensitization/resensitization

What are the common components of the interceullular signaling system?

Ligands: chemical signals, usually water soluble, extracellular compounds

Receptors: usually residing within the membrane

Second messengers: inside of the cell are produced following ligand-receptor interaction and are usually metabolites of abundant, pre-existing cellular components

Signal transduction: often involves a cascade of protein phosphorylation reactions in which protein kinase enzymes can be activated catalytically by phosphorylation and then activate 'downstream' kinases

What are the major classes of signal transduction networks?

Degradation of receptor

Hydrolysis of cAMP

Dephosphoryation

Diffusion of ligands

What are the types of feedback and control mechanisms operative in representative signaling systems?

Example in Kinase Cascades:

• A series of protein phosphorylation reactions

• protein kinases are catalytically activated by phosphorylation (utilizing ATP)

  • sequentially activate "downstream" kinases to amplify the signal exponentially

Role of protein phosphorylation in cell signal transduction

Comparative molecular pattern matrix (7): similarities in molecular patterns