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Neuroscience > Aquaporins > Flashcards

Aquaporins Flashcards

1
Q

Discovery of AQP evidence

A

CHIP28 transfection oocytes- water permeability

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2
Q

Structure of AQP1

A

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

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3
Q

Water/ glycerol movement through AQP

A

Hydrophobic residues promote water movement

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4
Q

AQP6 role in chloride transport

A

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

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

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5
Q

AQP1 expression in proximal kidney

A

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

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6
Q

AQP1 KO effects

A

AQP1 WT and AQP4 WT vs AQP1KOs

  • INCREASE in urine osmolality
  • Body Weight
  • Lethargy
  • Organ morphology unchanged on physiological examination
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7
Q

AQP1 KO water permeability

A

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

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

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8
Q

AQP1 effect on CCM

Evidence of no AQP1 in DTL

A

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

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9
Q

AQP1 in vasa recta

A

KOs: reduced water permeability

Increased diameter of Vasa recta

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10
Q

AQP1 in peritoneal transport

A

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

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11
Q

AQP1 contributes to

Wang 2015

A

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

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12
Q

Water permeability in CCD

A

Osmotic water permeability in response to ADH

Vasopressin increases water permeability during application

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13
Q

Expression of AQP2 in response to vasopressin

A

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

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14
Q

AVP pathway

Critical role of Ser256 in AQP2 expression

A

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

Inhibition of PKA with H89- reduced APM:IV ratio

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15
Q

Role of PKC on decreasing AQP2 expression

A

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

PMA + forksolin mutate Ser256s

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16
Q

Long term AQP2 expression control

A

EPAC1
- differential expression in different tubule regions immunohistochemistry

Upregulation of PKA
Reduction in PKC inhibition

17
Q

AQP2 expression and stimuli

A

AVP infusion AQP2 expression
Dehydration
Overhydration (induces hyponatraemia)

18
Q

AQP1 in CSF Production

A

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

19
Q

AQP1 and ICP

A

AQP1KOs vs WT, AQP3KOs

Gravity increases- reduces expression

20
Q

AQP1 and prognosis

A

Cold-induced brain injury

-survival times, ICP

21
Q

AQP1 in spinal cord

A

Fluorescent staining C fibres

KOs- nociception, hot plate test

22
Q

AQP4 Cytotoxic oedema

A

Mortality
Hemispheric enlargement
Water intoxication
Meningitis model- neurological score

23
Q

AQP4 Vasogenic oedema

A

evans blue does not cross BBB- cold induced injury

tumour vasogenic oedma model- neurological score

24
Q

AQP4 Vasogenic oedema

A

evans blue does not cross BBB- cold induced injury

tumour vasogenic oedma model- neurological score

25
Q

AQP4 coexpression with Kir4.1 in astrocytes

Contrasting evidence

A

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

26
Q

AQP4 and plasticity

A

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

27
Q

AQP9 expression in ischaemic stroke

A

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

28
Q

AQP1 and 4 in cell migration

A

Expression in CHO/FRT cell lines

Chemotactic assay and scratch assay

29
Q

AQP1- tumorigenesis and angiogenesis

A 
Tumour size
invasiveness
No. blood vessels
Necrotic tissue
survival
30
Q

AQP4 migration

A 
Phosphorylation at Serine180 reduces permeability and migration
PKC agonist (PMA)
PKC antagonist (Chelerythrine)

PLC inhibitor also decreases migration

31
Q

AQP 1 and foetal development

A

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

32
Q

CV disease and AQP1

A

Rabbits
Increased AQP1 mRNA and protein following MI
Peak at Day 7

KO mice
HR, O2 consumption
LV mass, thickness and diffusion distance

33
Q

AQP2 in diabetes insipidus

A

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

34
Q

AQP2 in chronic heart failure- rat studies and treatments

A

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

Neuroscience (17 decks)

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