1. Bio 201 - Cell Biology Dr. Hutson Lecture 20 – Review March 14, 2014

2. Review topics Motor proteins Signal transduction all Other

3. Signal transduction: what it is How cells interpret (i.e. “transduce”) signals from other cells. Involves ligand binding to a receptor, usually on the cell surface. – High affinity – Specificity Conformational change in receptor is key to intracellular response. Intracellular response often involves complex, multi-step pathways Sometimes involves a second messenger: soluble molecule produced in response to ligand binding; responsible for activation of next step in pathway

4. “Modes” of signaling between cells Juxtacrine and Contact-dependent: very fast and specific to cells in immediate surroundings Paracrine: relatively fast, affects more cells Endocrine: much slower, affects many different cells throughout organism; good for coordinating cellular responses

5. Different ligands may bind to different types of receptors. Different receptors transduce qualitatively different types of responses. GPCRs: AC β β α α cAMP ras PKA MAPK Many different types of ligands Growth factors RTKs: enzymes txn Response to ligand binding usually involves changes in enzyme activity Relatively fast Reversible Response amplification Response to ligand binding usually involves changes in transcriptional activity Slower Not necessarily reversible b/c enzymes involved, amplification Υ Υ Many different responses Growth, proliferation

6. Different ligands may bind to different types of receptors. Different receptors transduce qualitatively different types of responses. Steroid hormones txn Steroid hormone Rs: Response to ligand binding almost always involves changes in transcriptional activity Slower Not necessarily reversible No amplification (no enzymes) Many different responses, incl. growth, differentiation

7. The same ligand may have different effects on different types of cells. This is sometimes due to the fact that different cells have different targets of Gα. Liver: AC β β α α cAMP PKA Epinephrine enzymes Υ Υ Some blood vessels and sweat glands: β β α α Epinephrine Υ Υ PLC IP3 Ca ++ Contraction (some blood vessels); Secretion (sweat glands) Glycogen breakdown glucose

8. In other cases, it is due to the fact that different cells have different targets of PKA. Liver: AC β β α α cAMP PKA Epinephrine Υ Υ Glycogen breakdown glucose Bronchial smooth muscle cells: Epinephrine Bronchodilation AC β β α α cAMP PKA Υ Υ

9. Analyzing the effects of activators and inhibitors AC β β α α cAMP PKA Epinephrine Υ Υ GTP Glycogen breakdown  glucose (and inhibition of glycogen production)

10. Motor proteins - Myosin Function: Muscle contraction, actin retraction in amoeboid cells Interacts with: actin Direction: + end directed Myosin is anchored + - + - ATP binds + -

11. Motor proteins - Kinesin Function: Organelle transport Interacts with: Microtubules Direction: + end directed Kinesin is bound to vesicle or organelle (NOT anchored) + - ATP binds + -

12. Motor proteins - Dynein Function: Organelle transport; cilia and flagella Interacts with: Microtubules Direction: - end directed Mechanistically similar to kinesin, but going in the opposite direction.

13. Comparison of motor proteins