Aquaporins

Question 1

Discovery of AQP evidence

Answer 1

CHIP28 transfection oocytes- water permeability

Question 2

Structure of AQP1

Answer 2

Hydrophobicity plot
B and E loops hydrophobic
Cytoplasmic C and N termini
Glycosyl chain on one monomer of 4

Question 3

Water/ glycerol movement through AQP

Answer 3

Hydrophobic residues promote water movement

Question 4

AQP6 role in chloride transport

Answer 4

Colocalised with H+ATPase
AQP6 channels most active at acidic pHs e.g. pH4

Fluorescent protein tagging permeabilities to NO3, Cl-, Iodide etc.

Question 5

AQP1 expression in proximal kidney

Answer 5

Osmotic water movement permeability
AQP1 gold particle expression
-Proximal tubule, Descending Limb, Vasta recta

Question 6

AQP1 KO effects

Answer 6

AQP1 WT and AQP4 WT vs AQP1KOs

• INCREASE in urine osmolality
• Body Weight
• Lethargy
• Organ morphology unchanged on physiological examination

Question 7

AQP1 KO water permeability

Answer 7

Schnermann: in vitro proximal tubule microperfusion; in vivo micropuncture of tubules

Near-water isomolar reabsorption
Compensatory decrease in GFR, and an increased osmotic gradient

Question 8

AQP1 effect on CCM

Evidence of no AQP1 in DTL

Answer 8

AQP1 KOs: lower water permeability in KOs
?no expression of AQP1 in human and rat in short loop thin limbs (90%)
AAV-AQP1 rescue did not produce a rescue

Question 9

AQP1 in vasa recta

Answer 9

KOs: reduced water permeability

Increased diameter of Vasa recta

Question 10

AQP1 in peritoneal transport

Answer 10

Sucrose infusion measuring albumin tracer via catheter in mice
decreased in AQP1 KO mice
AQP4 control

Question 11

AQP1 contributes to

Wang 2015

Answer 11

AQP1 null PKD mice had more, larger PCT cysts
AQP1 reduced growth of cysts in vitro

Pkd1 associated with increased B-catenin pathway activation
Western blot analysis demonstrates that B-catenin phosphorylation is decreased in KOs- may be associated with cyst formation

Question 12

Water permeability in CCD

Answer 12

Osmotic water permeability in response to ADH

Vasopressin increases water permeability during application

Question 13

Expression of AQP2 in response to vasopressin

Answer 13

Gold particle staining APM:IV ratio
Increased upon AVP stimulation
Reverse translocation

Question 14

AVP pathway

Critical role of Ser256 in AQP2 expression

Answer 14

AVP- V2R- PKA- phosphorylates Ser256
Ala (not), Asp (permanently)

Inhibition of PKA with H89- reduced APM:IV ratio

Question 15

Role of PKC on decreasing AQP2 expression

Answer 15

PMA activates PKC- decreased expression
Ro31-8220 inhibits- increased expression

PMA + forksolin mutate Ser256s

Question 16

Long term AQP2 expression control

Answer 16

EPAC1
- differential expression in different tubule regions immunohistochemistry

Upregulation of PKA
Reduction in PKC inhibition

Question 17

AQP2 expression and stimuli

Answer 17

AVP infusion AQP2 expression
Dehydration
Overhydration (induces hyponatraemia)

Question 18

AQP1 in CSF Production

Answer 18

Light-Perfusion chamber- water transport across choroid
KOs- decreased
Forskolin- drives solute secretion- greater osmolality difference

Question 19

AQP1 and ICP

Answer 19

AQP1KOs vs WT, AQP3KOs

Gravity increases- reduces expression

Question 20

AQP1 and prognosis

Answer 20

Cold-induced brain injury

-survival times, ICP

Question 21

AQP1 in spinal cord

Answer 21

Fluorescent staining C fibres

KOs- nociception, hot plate test

Question 22

AQP4 Cytotoxic oedema

Answer 22

Mortality
Hemispheric enlargement
Water intoxication
Meningitis model- neurological score

Question 23

AQP4 Vasogenic oedema

Answer 23

evans blue does not cross BBB- cold induced injury

tumour vasogenic oedma model- neurological score

Question 24

AQP4 Vasogenic oedema

Answer 24

evans blue does not cross BBB- cold induced injury

tumour vasogenic oedma model- neurological score

Question 25

AQP4 coexpression with Kir4.1 in astrocytes Contrasting evidence

Answer 25

Gold particle co-localisation greatest at foot processes A-Syntrophin KO- gold particle colocalisation Generalised hyperthermia induced seizures susceptibility BUT In hippocampus, AQP4 expressed in CA1 and dentate gyri KOs of either Kir4.1 or AQP4 does not affect other Effect may be mediated by an expansion of ECS- increasing tumour susceptibility

Question 26

AQP4 and plasticity

Answer 26

KOs Basal transmission unaffected Affected LTD and LTP in one induction protocol Object placement memory test

Question 27

AQP9 expression in ischaemic stroke

Answer 27

Increases Increased expression of AQP9 in diabetes- may be involved in energy metabolism - removal of lactate after stroke

Question 28

AQP1 and 4 in cell migration

Answer 28

Expression in CHO/FRT cell lines | Chemotactic assay and scratch assay

Question 29

AQP1- tumorigenesis and angiogenesis

Answer 29

``` Tumour size invasiveness No. blood vessels Necrotic tissue survival ```

Question 30

AQP4 migration

Answer 30

``` Phosphorylation at Serine180 reduces permeability and migration PKC agonist (PMA) PKC antagonist (Chelerythrine) ``` PLC inhibitor also decreases migration

Question 31

AQP 1 and foetal development

Answer 31

KOs -Greater volume of dilute amniotic fluid -Chorionic plates unable to reabsorb excessive fluid AQP1 in lung- effects on production

Question 32

CV disease and AQP1

Answer 32

Rabbits Increased AQP1 mRNA and protein following MI Peak at Day 7 KO mice HR, O2 consumption LV mass, thickness and diffusion distance

Question 33

AQP2 in diabetes insipidus

Answer 33

NDI: Kidneys not responsive to AVP- x linked mutation of V2R gene -inducible by lithium administration- reduces expression of AQP2 dehydration re-increases levels

Question 34

AQP2 in chronic heart failure- rat studies and treatments

Answer 34

CHF-induced rats AQP2 expression apical membrane- immunoblotting May be due to increased AVP levels Could explain water retention -oedema, hyponatraemia V2R antagonists (Tolvaptan, Satavaptan) EVEREST trial No benefits long term prognosis May improve fluid balance, dyspnoea, oedema in acute exacerbations