Lecture 14 Vesicular Transport II

Question 1

what are the membrane compartments of lysosome filled with

Answer 1

hydrolytic enzymes

Question 2

what is the function of lysosomes

Answer 2

intracellular digestion of macromolecules

Question 3

what type of enzymes are found in lysosomes

Answer 3

proteases 
nucleases
gylcosidases
lipases
phospholipase
phosphates
sullfatases

Question 4

what do lysosomes require for optimal activation

Answer 4

acidic environment

proteolytic cleavage

Question 5

vacuolar ATPase

Answer 5

pumps H+ into lysosomes to maintain acidic pH and drive transport of small metabolites

Question 6

what does the Trans-Golgi network deliver to lysosomes

Answer 6

membrane proteins and hydrolyses

Question 7

steps in co-translation transport of membrane proteins and hyrolases to lysosome in TGN

Answer 7

into rough Er

then transported via Golgi comes to TGN

Question 8

TGN buds off Golgi to form

Answer 8

endosomes

these develop into lysosomes

Question 9

what do lysosomal hydrolyses have that attach them in the CGN

Answer 9

sorting signal

Question 10

sorting signal of lysosomal hydrolyses

Answer 10

Mannose 6 Phosphate

Question 11

what do M6P receptors in TGN recognize

Answer 11

sorting signal sugar, M6P

Question 12

after hydrolyses bind to TGN…

Answer 12

they are packaged into clathrin coated vesicles that bud off and delivered to endosomes then lysosomes

Question 13

steps of lysosomal protein sorting

transport of newly synthesized lysosomal hydrolases to lysosomes

Answer 13

1. on cis-Golgi mannose binds to hydrolase from ER and phosphate is added – becomes M6P
2. M6P signal is uncovered as it moves thru Golgi
3. M6P binds to M6P receptor, gets clathrin coated and buds off
4. Transport to endosome, fusion with endosome
5. hydrolyses dissociate from M6P receptors (due to low pH)
6. Empty transports are recycled back to the TGN
7. in endosomes, phosphate is removed and hydrolyses are kept in the endosome

Question 14

what is the enzyme responsible for recognizing the lysosomal hydrolase?

Answer 14

GlCNAc phosphotransferase

Question 15

how does the lysosome recognize the hydrolase

Answer 15

signal patch binds to the phsphotransferase

Question 16

binding site of phosphotransferase binds

Answer 16

high mannose N-linked oligosaccharides

UDP-GLCNAc

Question 17

steps in lysosomal recognition

Answer 17

1. binding of signal path to recognition site of phosphotransferase
2. transfer of GlcNAc-P to mannose at catalytic site
3. release
4. remold of GLcNAc

Question 18

lysosomal storage disease

Answer 18

caused by genetic defects in lysosomal hydrolyses

results in accumulation of undigested material in lysosome

Inclusion Cell disease
Hurlers Disease
Missing GlcNAc phosphtransferase

Question 19

Hurlers disease

Answer 19

mutation in the enzyme required to break down glycosaminoglycan chains

lysosomal storage disease

Question 20

Inclusion Cell Disease

Answer 20

missing hydrolyses in cell types

substrates accumulate as inclusions

Question 21

missing GlcNAc phosphotransferases cause

Answer 21

enzymes that aren’t phosphorylated and therefore not sorted into vesicles and delivered into lysosomes but instead are carried to cell surface and found in blood

Question 22

transport mechanisms in this lecture

Answer 22

1. Transport from TGN to Lysosomes
2. endocytosis
3. exocytosis

Question 23

endocytosis

Answer 23

uptake of macromolecules from exterior across plasma membrane

Question 24

pinocytosis

Answer 24

form of endocytosis

small particles are ingested by pinocytic vesicles

Question 25

phagocytosis

Answer 25

form of endocytosis large particles are ingested by phagosomes

Question 26

receptor mediated endocytosis

Answer 26

used to import macromolecules from outside cells molecules bind to receptors on membrane surface then accumulate in clathrin coated pits provides selective concentration mechanisms

Question 27

what is an example of receptor mediated endocytosis

Answer 27

cholesterol uptake blockage of this pathway results in atherosclerosis

Question 28

role of clathrin coated pits in receptor mediated endocytosis

Answer 28

LDL receptors associate with clathrin-coated pits that then pinch off, carrying LDL particles and receptors LDL particles are freed into extracellular space when clathrin is removed

Question 29

steps of cholesterol uptake

Answer 29

1. endocytosis 2. uncaring 3. fusion with endosome 4. budding off of transport vesicles 5. return of LDL receptors to plasma membrane

Question 30

sequestering of endocytose proteins

Answer 30

1. covalent modification with ubiquitin-- requires only 1 ubiquitin 2. ubiquitin tag facilitates the uptake of the receptors into endocytic vesicles 3. ubiquitin is recognized by proteins that mediate the sorting process into the internal membrane vesicles of multi vesicular bodies Lipid kinase helps regulate by phosphorylating phosphatidylinositol serve as docking sites for the proteins that mediate the invagination proces

Question 31

possible fates of endocytose receptor proteins

Answer 31

1. recycled transport vesicles 2. degradation by endolysosome 3. transcytosis of transport vesicle

Question 32

what type of cells use phagocytosis?

Answer 32

macrophages and neutrophils | phagosomes

Question 33

macrophages and neutrophils use phagocytosis by

Answer 33

ingesting invading microorganisms to protect against infection scavenge senescent and apoptotic cells

Question 34

mechanism of phagocytosis ex. antibody interaction

Answer 34

1. antibodies bind to microbe 2. Fc chain recognized by Fc receptor on surface of WBC 3. pseudopod is formed and engulfs particle to form phagosome

Question 35

what triggers phagocytosis?

Answer 35

binding of a particle to receptors on phagocyte surface

Question 36

formation of pseudopod is driven by:

Answer 36

localized actin polymerization and reorganization

Question 37

formation of pseudopod is controlled by

Answer 37

Rho GTPases | phosphoinostitide signaling

Question 38

pinocytosis

Answer 38

cells ingest bits of PM in form of small pinocytotic vesicles begins at clathrin coated vesicle extraceullar fluid is trapped with solutes as they invaginate

Question 39

flask shaped invaginations in PM

Answer 39

caveolae

Question 40

caveolae

Answer 40

enriched in cholesterol and glycosphingolipids caveoloae ingavingate into membrane by lipid composition don't connect with lysosomes

Question 41

structural protein of caveolae

Answer 41

caveolin

Question 42

exocytosis

Answer 42

transport from TGN to cell exterior fusion of vesicles with PM

Question 43

____ secretory pathway operates continuously

Answer 43

constitutive

Question 44

____ secretory pathway is triggered by signals

Answer 44

regulated signal combines with secretory vesicle and it is fused with membrane

Question 45

three mechanisms of protein sorting in TGN

Answer 45

1. signal mediated diversion to lysosomes 2. signal mediated diversion to secretory vesicles 3. constitutive secretory pathway

Question 46

formation of secretory vesicles

Answer 46

involves selective aggregation/clumping of proteins TGN promotes proteolytic processing of the proteins

Question 47

steps in formation of synaptic vesicle

Answer 47

1, delivery of synaptic vesicle membrane components to presynaptic plasma membrane 2. endocytosis of synaptic vesicle membrane components to form new synaptic vesicles directly 3. endocytosis of synaptic vesicle membrane components \ and delivery to endosome 4. budding of synaptic from endosome 5. loading o fNeurotransmitter into synaptic vesicle 6. secret of Neurotransmitter by exocytosis