Lecture 14: Vesicular Trafficking 2

Question 1

Lysosomes require ____ environment and ____ cleavage for optimal activation

Answer 1

acidic, proteolytic

Question 2

_____ pump H+ into lysosomes to maintain the acidic pH and to drive transport of small metabolites

Answer 2

Vacuolar ATPases

Question 3

Lysomsomes contain about 40 types of enzymes such as

Answer 3

• Proteases, nucleases, glycosidases, lipases, phospholipases, phosphatases, and sulfatases

Question 4

an early endosome becomes a late endome after

Answer 4

microtubul-mediated transport

Question 5

a late endosomes can fuse with lysosomes to become

Answer 5

endolysosomes

Question 6

early endosomes come from

Answer 6

plasma membrane and trans golgi network

Question 7

Lysosomal hydrolases have the sorting signal ____ attached to them in the CGN

Answer 7

mannose-6-phosphate (M6P)

Question 8

M6P receptors in ____ recognize the sugar. the recepotrs bind hydrolases and to adaptor proteins in assembling clathrin coats. Packaged into ______ that bud from ____

Answer 8

• Trans Golgi Network (TGN)
• Clathrin-coated vesicles that bud form TGN

Question 9

_____ recognizes lysosomal hydrolases in the Golgi apparatus

Answer 9

GlcNAc phosphotransferase

Question 10

Lysosomal Storage Diseases

Answer 10

• Genetic defects in lysosomal hydrolases
• Leads to accumulation of undigested material in lysosomes
• Ex
  
  • Hurler’s disease
    
    • mutation in the enzyme required to break down glycosaminoglycan chains
  • Inclusion Disease
    
    • all the lysosomal hydrolases are missing in many cell types. Undigested substrates accumulate as “inclusions”
  • Defective or missing GlcNAc phosphotransferase (this is a major cause of inclusion-cell disease)
    
    • GlcNAc phosphotransferase is an enzyme that adds M6P to lysosomal hydrolases. The enzymes are not phosphorylated and hence not sorted into vesicles and not delivered into lysosomes
    • instead they are carried to cell surface and secreted (thus found in blood)

Question 11

Large particles ingested by vesicles are called ____

Answer 11

phagosomes (phagocytosis)

Question 12

Small particles ingested by pinocytic vesicles a process called

Answer 12

pinocytosis

Question 13

The conversion of early endosomes ot late endosomes is accompanied by loss of the _______

Answer 13

tubular projections

Question 14

what is the best example of receptor-mediated endocytosis

Answer 14

Cholesterol uptake

Question 15

Receptor-mediated Endocytosis

Answer 15

• used ot import select macromolecules from outside cell
• Molecules bind ot receptors on membrane surface
• Accumulate in clathrin-coated pits
• enter cell as receptor-macromolecular complex in clathrin-coated vesciles
• Provides selective concentration mechanisms
• (blockage of this pathway leads to atherosclerosis)

Question 16

Blockage of receptor mediated Endocytosis leads to

Answer 16

Atherosclerosis

Question 17

The sequestration of endocytosed proteins into intralumenal vesicles of multivesicular bodies is done how?

Answer 17

• Ubiquitylated membrane proteins are sorted into domain on the endosome memebrane, which invaginate and pinch off to form intralumenal vesicles. The ubiquitin marker is removed and returned to the cytosol for reuse before the intralumenal vesicle closes.

Question 18

Possible fates for transmembrane receptor proteins that have been endocytosed

Answer 18

• Retrieved receptors are returned to the same plasma membrane domain form which they came (recycling) or via a recycling endosome to a different domain of the plasma memebrane (transcytosis)
• Receptors that are not specifically retrieved from early or recycling endomes follow the pathway form the endosomal compartment to lysosomes, where they are degraded (degradation)

Question 19

Recycling endosomes can serve as an _____ site for specialized plasma membrane proteins that can be mobilized when needed. Ex?

Answer 19

• intracellular storage site
• ex. Insulin binding to insulin receptor triggers an intracellular signaling pathway that causes the rapid insertion of glucose transporters into the plasma membrane of a fat or muscle cell, greatly increasing its glucose intake

Question 20

Examples of phagocytes

Answer 20

Macrophages and Neutrophils

Question 21

Antiboides bind to microbe, Fc chain recognized by Fc receptor on surface of macrophages/neutrophils triggers formation of _____ which engulfs the particle and forms a ____

Answer 21

• Pseudopod
• Phagosome

Question 22

Pseudopod formation is driven by localized _____ and _____ and is controlled by

Answer 22

• actin polymerization and reorganization
• and is controlled by Rho GTases and Phosphoinositide signaling (PI (4,5)P₂ stimulates actin polymerization, which promotes pseudopod formation, and then PI (3,4,5)P₃ depolymerizes actin filaments at the base.

Question 23

Pinocytosis or ‘cell drinking’ is a constitutive process and occurs continuously in all eukaryotic cells. cells ingest bits of the ____ in the form of small pinocytic vesicles

Answer 23

Plasma membrane (macrophages ingest about 3% of its membrane every minute)

Question 24

The process of pinocytosis begins at _______

Answer 24

clathrin-coated pits

Question 25

_____ are flask-shaped invagination in Plasma membrane. Enriched in cholesterol and glycospinogolipids, and GPI-anchored membrane proteins

Answer 25

Caveolae

Question 26

what is the major structural protein of Caveolae

Answer 26

Caveolin

Question 27

Caveolae invaginate into membrane by virtue of _________ and not the protein coat

Answer 27

lipid composition

Question 28

Caveolae pinch off form PM by

Answer 28

dynamin

Question 29

do Caveosome (endosome-like compartment) connect with lysosomes

Answer 29

No

Question 30

Transport vesicles move from TGN to PM. Fusion of vesicles with PM called ___

Answer 30

exocytosis

Question 31

The constitutive and regulated secretory pathways diverge in the

Answer 31

Trans Golgi network

Question 32

____ secretory pathway operates in all cells. Meanwhile specialized secretory cells also have a _____ secretory pathway

Answer 32

• Constitutive
• Regulated

Question 33

The constitutive secretory pathway delivers proteins with _____ special signaling features to the cell surface

Answer 33

No

Question 34

The trans-SNARE complex responsible for docking synaptic vesicles at the plasma membrane of nerve terminals consists of three proteins. Which are?

Answer 34

• v-SNARE synaptobrevin (transmembrane proteins)
• t-SNARE syntaxin (transmembrane proteins)
• t-SNARE SNAP25 (peripheral membrane protein)

Question 35

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