1. Chapter 13
Intracellular Vesicular Traffic

2. Vesicular transport

3. The endocytic and biosynthetic-secretory pathways

4. The three well-characterized types of coated vesicles differ in their
coat proteins

5. Utilization of different coats in vesicular traffic

6. Assembly of a clathrin coat drives vesicle formation
Clathrin-coated pits and vesicles

7. The structure of a clathrin coat

8. The assembly and disassembly of a clathrin coat
The pinching-off and uncoating of coated vesicles are regulated processes
The assembly and disassembly of a clathrin coat

9. Not all coats form basketlike structures
A model for retromer assembly on endosomal membranes

10. Phosphoinositides mark organelles and membrane domains

11. The intracellular location of phosphoinositides

12. leaflets of the lipid bilayers flow together
The role of dynamin in pinching off clathrin-coated vesicles from the membrane
Dynamin together with other proteins destabilize the membrane so that the noncytoplasmic
leaflets of the lipid bilayers flow together

13. The coats of COPI and COPII vesicles consists of large
protein complexes that are composed of
- seven individual coat-protein subunits for COPI coats, and
- four individual coat-protein subunits for COPII coats
Some COPI coat-protein subunits show sequence similarity to
adaptins

14. Vesicular transport does not necessarily occur only through
uniformly sized spherical vesicles, but can involve larger
portions of a donor compartment

15. Monomeric GTPases control coat assembly
Assembly of a COPII-coated vesicle

16. Rab proteins guide vesicle targeting

17. SNARE proteins and targeting GTPases guide membrane transport
SNAREs contribute to the selectivity of transport-vesicle docking and fusion, while the
GTPases (Rabs) regulate the initial docking and tethering of the vesicle to the target membrane

18. The formation of a Rab5 domain on the endosome membrane

19. SNAREs mediate membrane fusion
Structure of a trans-SNARE complex

20. A model for how SNARE proteins may ccatalyze membrane fusion

21. Interacting SNAREs need to be pried apart before they can function again

22. Viral fusion proteins and SNAREs may use similar fusion mechanisms
The entry of enveloped viruses into cells

24. Proteins leave the ER in COPII-coated transport vesicles

25. Only proteins that are properly folded and assembled can leave the ER

26. Homotypic membrane fusion
Transport from the ER to the Golgi apparatus is mediated by
vesicular tubular clusters
Homotypic membrane fusion

27. Vesicular tubular clusters move along the microtubules to carry
proteins from the ER to the Golgi apparatus

28. The retrieval pathway to the ER uses sorting signals
The best-characterized signal for ER membrane proteins is KKXX present at the C-terminus
and this signal interacts directly with the COPI coat .
Soluble ER resident proteins contain the signal sequence KDEL at their C-terminus and this
signal interacts with the KDEL receptor, a multipass transmembrane protein.

29. cluster and the Golgi apparatus
The pH-dependent retrieval of ER resident proteins from the vesicular tubular
cluster and the Golgi apparatus
Many proteins are retained in the ER as a result of kin recognition

30. The length of the transmembrane region of Golgi enzymes
determines their location in the cell

31. The Golgi apparatus consists of an ordered series of compartments

33. Molecular compartmentalization of the Golgi apparatus

34. Oligosaccharide chains are processed in the Golgi apparatus

35. The two main classes of N-linked oligosaccharides found in mature mammalian glycoproteins

36. Oligosaccharide processing in the ER and the Golgi apparatus

37. Proteoglycans are assembled in the Golgi apparatus

38. Two possible models for transport of proteins through the Golgi apparatus

40. Lysosomes are the principal sites of intracellular digestion

41. A model for lysososme maturation

42. Multiple pathways deliver materials to lysosomes

43. A mannose 6-phosphate receptor recognizes lysosomal proteins in the
trans Golgi network

44. The M6P receptor shuttles between specific membranes

45. A signal patch in the hydrolase provides the cue for M6P addition

46. Endocytosis
Two main types of endocytosis distinguished on the basis of the size of the endocytic vesicle
formed.
Phagocytosis involves ingestion of large particles and is a triggered process.
Pinocytosis involves ingestion of fluid and solutes via small pinocytic vesicles and is a
constitutive process that occurs continuously

47. Specialized phagocytic cells can ingest large particles
A macrophage ingesting red blood cells

48. Phagocytosis by a neutrophil

49. Pinocytic vesicles form from coated pits in the plasma membrane
Formation of clathrin-coated vesicles from the plasma membrane

50. Not all pinocytic vesicles are clathrin-coated
Caveolae in the plasma membrane of a fibroblast

51. Cells import selected extracellular macromolecules by receptor-mediated endocytosis
Most cholesterol is transported in the blood as low-density lipoprotein (LDL) particles

52. Normal and mutant LDL receptors

53. The receptor-mediated endocytosis of LDL

54. Possible fates for transmembrane receptor proteins that have been endocytosed

55. Exocytosis

56. Constitutive secretory pathway – all cells
Regulated secretory pathway – found mainly in specialized cells

57. The three best-understood pathways of protein sorting in the trans Golgi network

58. Secretory vesicles bud from the trans Golgi network

59. Exocytosis of secretory vesicles

60. Proteins are often proteolytically processed during the formation of
secretory vesicles
Alternative processing pathways for the prohormone proopiomelanocortin

61. Polarized cells

62. Sorting of plasma membrane proteins in a polarized epithelial cell

63. Most synaptic vesicles are generated by local recycling from the plasma membrane
in the nerve terminals

64. A model of a synaptic vesicle