Retinal Pigment Epithelium Physiology (F)

Question 1

What is the organelle responsible for light absorption? 1. When is it formed? 2

Answer 1

1. Melanosome

2. development and none after that

Question 2

What is a lack of melanin pigment in the RPE called? 1. What does it result in? 2

Answer 2

1. Ocular Albinism

2. improper routing of ganglion cells through the optic chiasm (binocular)

Question 3

What fails to develop in eyes without melanosomes?

Answer 3

the fovea

Question 4

What are melanosomes derivatives of? 1. How do they mature? 2

Answer 4

1. early sorting endosomes

2. intracellular vesicular trafficking and incorporation of vesicles containing melanosome specific proteins

Question 5

What are the first two stages of melanosome formation characterized by?

Answer 5

intralumenal proteinaceous fibrils that begin to form in stage I and are completed by stage II

Question 6

What stage is melanin deposited? 1. What is the enzyme that initiates melanin synthesis? 2

Answer 6

1. III and IV

2. Tyrosinase

Question 7

What are the non-enzymatic antioxidants to neutralize ROS in the RPE?

Answer 7

Superoxide dismutase, catalase, Glutathione, ascorbate, melanin

Question 8

What are the non-enzymatic antioxidants to neutralize ROS in the RPE?

Answer 8

Superoxide dismutase, catalase, Glutathione, ascorbate, melanin

Question 9

What are the glucose transporters in the RPE? 1. Which one has increased expressing in the presence of HIF-1? 2.

Answer 9

1. GLUT1, GLUT3

2. GLUT1

Question 10

What is incorporated into glycerolipids for synthesis and storage of fatty acids and is essential for the renewal process of the photoreceptor out segment membranes?

Answer 10

Docosahexaenoic acid (DHA)

Question 11

What is the driving force of the constant removal of water from the RPE?

Answer 11

chloride ions

Question 12

What transport water from the inner retina? 1. From the outer retina? 2

Answer 12

1. Muller cells

2. RPE cells

Question 13

Where are the Na+-K+-ATPase (NKA) channels? 1. What do they move and where? 2. Do they require ATP? 3.

Answer 13

1. apical
2. 3 Na+ out, 2 K+ in
3. yes

Question 14

Where are the rectifying potassium channels (Kir)? 1. What do they move and where? 2. Do they require ATP? 3.

Answer 14

1. apical
2. K+ out
3. no

Question 15

Where are the rectifying potassium channels (Kir)? 1. What do they move and where? 2. Do they require ATP? 3.

Answer 15

1. apical
2. K+ out
3. no

Question 16

Where are the NKCC co-transporters? 1. What do they move and where? 2. Do they require ATP? 3.

Answer 16

1. apical
2. Na+ in, K+ in, 2 Cl-
3. no

Question 17

What drives water into the RPE cells via aquaporins (AQP1)?

Answer 17

intracellular chloride ions

Question 18

Where are the CLC-2 Cl- channels? 1. What do they move and where? 2. Do they require ATP? 3.

Answer 18

1. basal
2. Cl- out
3. no

Question 19

Where are the Ca2+ dependent Cl- channels? 1. What do they move and where? 2. Do they require ATP? 3.

Answer 19

1. basal
2. Cl- out
3. no

Question 20

Where are the cAMP regulated Cl- channels? 1. What do they move and where? 2. Do they require ATP? 3.

Answer 20

1. basal
2. Cl- out
3. require cAMP

Question 21

Does water flow in or out of the RPE cell on the basal end?

Answer 21

out

Question 22

What happens in the light to the Na+, K+ and H2O in the subretinal space?

Answer 22

1. Decrease in subretinal K+
2. Increase in Na+
3. Increase in H2O

Question 23

What happens in the light to the Na+, K+ and H2O in the subretinal space?

Answer 23

1. Decrease in subretinal K+
2. Increase in Na+
3. Increase in H2O

Question 24

Where are the Na+/H+ exchangers? 1. What do they move and where? 2. What is the driver? 3

Answer 24

1. apical
2. Na+ in, H+ out
3. sodium gradient

Question 25

Where are the MCT1 (monocarboxylate transporter) cotransporters? 1. What do they move and where? 2. What is the driver? 3

Answer 25

1. apical 2. H+ and lactate in 3. pH gradient and the high [lactate-] in the subretinal space

Question 26

Where are the MCT3 (monocarboxylate transporter) cotransporters? 1. What do they move and where? 2.

Answer 26

1. basal | 2. H+ and lactate out

Question 27

When the extracellular pH is high what is the movement of HCO3-? 1. When low? 2

Answer 27

1. retina to choroid | 2. choroid to retina

Question 28

What channel is pH sensitive?

Answer 28

CLC-2

Question 29

An increase in the transport of lactate leads to what regarding the intracellular pH? 1. Cl-? 2. Water transport? 3

Answer 29

1. intracellular acidification 2. increase 3. increase

Question 30

An increase in the transport of lactate leads to what regarding the intracellular pH? 1. Cl-? 2. Water transport? 3

Answer 30

1. intracellular acidification 2. increase 3. increase

Question 31

What do rod photoreceptors depend on for the conversion of 11-trans to 11 cis and as a source of 11-cis-retinal? 1. What do cones depend on? 2

Answer 31

1. completely on RPE cells | 2. RPE cells and have an alternative pathway which CAN regenerate all-trans to 11-cis retinal

Question 32

After hydrolysis where does all-trans retinal become embedded?

Answer 32

the lumen (minority) or cytosolic membrane face (majority)

Question 33

Where is all-trans retinal found in the lumen side is “flipped” to? 1. What mediates this? 2

Answer 33

1. cytosolic side | 2. disc membrane localized ABCA4

Question 34

What retinal disorders are linked to mutation of the ABCA4 gene?

Answer 34

1. Stargardt disease 2. Cone-rod dystrophy 3. Age-related macular degeneration

Question 35

What is all-trans retinal converted to in the outer segment of the rod? 1. What mediates this? 2. What is required for this? 3

Answer 35

1. all-trans retinol 2. all-trans retinol dehydrogenase (RDH) enzyme 3. NADPH

Question 36

What delivers all-trans retinol to RPE cells?

Answer 36

interphotoreceptor matrix retinal binding protein (IRBP)

Question 37

Wat converts 11-cis retinOL to 11-cis retinAL? 1. Where does this occur? 2

Answer 37

1. retinol dehydrogenase (RDH) | 2. Retinosomes

Question 38

Wat converts 11-cis retinOL to 11-cis retinAL? 1. Where does this occur? 2

Answer 38

1. retinol dehydrogenase (RDH) | 2. Retinosomes

Question 39

11-cis retinAL is transported back to the rod outer segment while bound to what? 1. What does this protein do? 2

Answer 39

1. interphotoreceptor matrix retinal binding protein (IRBP) | 2. protects against oxidation

Question 40

Vitamin A (all-trans retinOL) is provided to the RPE cells from what? 1. What mediated this uptake? 2

Answer 40

1. choroid vasculature | 2. STRA6

Question 41

When is phagocytotic activity the highest in the retina?

Answer 41

in morning and peaks within 1-2 hours

Question 42

How often is a whole length of a photoreceptor outer segment renewed?

Answer 42

11 days

Question 43

What is required for engulfment and mutations of this gene cause Retinitis Pigmentosa (breakdown of rod photoreceptors)?

Answer 43

tyrosine kinase receptor MerTK

Question 44

What are membrane bound organelles with lysosomal properties found in the RPE? 1. What happens to these with age? 2

Answer 44

1. Lipofuscin vesicles | 2. increase abundance