1. Previously Bio308 Hypotheses for molecular basis of bipolar disorder Suggest problem lies in protein targeting How are proteins targeted and delivered? 3 Stages: Budding, targeting/docking and fusion How does a vesicle ‘know’ what components it should contain? How does it ‘know’ which membrane it should go to? How does it fuse when it gets there?

2. Budding Fig 17-58 http://biology-animations.blogspot.com/2009/10/clathrin-animation.html

3. Coat Components http://userpage.chemie.fu-berlin.de/biochemie/aghaucke/clath.jpg Clathrin COPI COPII Identity determined by what the vesicle contains and it’s coat.

4. Budding II ER vesicle budding Drin, G, and B. Antonny (2005) News and Views: Helices sculpt membrane. Nature vol: 437 Amino Acid Key Highly hydrophobic + charged - charged Other Hydroxylated Sar1p N-terminal helix Sar1p-GTP form exposes helix that anchors protein to ER surface by ‘floating’ with hydrophobic a.a. interacting with membrane core

5. Budding III Drin, G, and B. Antonny (2005) News and Views: Helices sculpt membrane. Nature vol: 437 ER vesicle budding Floating many Sar1p in top leaflet makes it ‘bigger’ than the bottom one. Results --> bulge that can more easily interact with coat proteins.

6. Fission ER vesicle budding….fission Ring of parallel helices at neck might aid fission. ‘New’ data for ER; had seen a protein (epsin) help deform PM for clathrin coated vesicles. May suggest that using a helix to deform membrane is common mechanism for budding/fission

7. Targeting/Docking: http://dir2.nichd.nih.gov/nichd/cbmb/sob/in_vivo_dyn.html What happens after budding? How do vesicles dock with specific target membrane?

8. The SNARE hypothesis Fig 17-59 V-SNARE T-SNARE Role of p115 Role of Rab proteins retrograde

9. Synaptic vesicle fusion VAMP Syntaxin SNAP 25 Synaptotagmin Rab3a

10. Endocytosis Endocytosis can be used to control the amount of a certain type of protein found at the surface Pinocytosis ‘problem’ rate of pinocytosis internalizes 100% of PM per hour ? (How can this be?) Maybe protein delivered correctly but problem lies in levels of recycling

11. Types of pinocytic vesicles Clathrin-coated Caveolae

12. Types of endocytosis Fluid phase– soluble components ‘got caught’ in vesicle Receptor-mediated– selected to be in vesicle Select how? Ligands bind receptors Receptors cluster Why do the receptors cluster and make a vesicle? Receptors have signaling sequences Signaling regions interact with adaptins Adaptins recruit coats  budding occurs

13. Separate: Recycle (R ) Degrade (L) Endocytosis– then what? Endosomal sorting Remove and Degrade (R & L) Transcytose

14. Distinguishing between types Similarities and differences between vesicles? Transport Exocytic Endocytic How could you tell them apart experimentally?

15. Neurotransmitters are stored in and secreted from vesicles. Neurotransmitter receptors are delivered to dendrite in vesicles. Could sorting and targeting problems be at the root of bipolar disorder? If sorting and targeting are the problems would you predict alteration of something like the NT receptor, or a SNARE or of a protein like NSF, SNAP25 ?

16. Molecular Roads and Infrastructure Bipolar disorder Is it the cellular equivalent of ‘dead letter box’? Are cytoskeletal ‘problems’ a likely cause for for this disorder? What are the components of the cytoskeleton and what do they do?