Beta Subunits Flashcards
What is a beta subunit?
Protein which does not have a role in forming an ion channel itself
Modulate the action of alpha subunits
E.g. KCNQ1 is an aplha subunit which has KCNE1 as a beta subunit
Barttin regulates CL- channel
Describe the KCNE family
5 types in epithelia
Vary in length from 103 to 177 amino acids
1 transmembrane spanning domain
KCNE1 is mutated in what?
Long QT syndrome
What are some of the actions of KCNE1, 2 and 3?
Some mean the K+ channel is voltage dependent
Others remove voltage dependence on the Q1 K+ channel
What happens when KCNE1 is overexpressed with KCNQ1 in oocytes?
When a two electrode voltage clamp is used the gaps between the currents increase with more positive potentials when Q1 is on its own
With E1 expression the current is larger but activation is slower and voltage dependence has shifted
Where is KCNE1 expressed in the kidney? How do we know this?
In the proximal tubule
Green rings on immunostaining at apical membrane of the brush border
Is the Q1 and E1 expression profile the same?
No - Q1 is also expressed in the distal tubule but E1 is not
How are clearance studies performed on mice?
- Jugular vein is cannulated for fluid replacement
- Bladder is cannulated for urine collection
- Carotid artery is cannulated to measure BP and to measure ion and solute concentration in the blood
- Rectal thermometer and heated pad keeps temperature of animal at 37 degrees
What was seen in E1 KO mice and clearance studies?
Plasma Na+ and Cl- was the same
GFR was the same also
However, plasma glucose concentration was lower in KO compared to WT BUT WT mice had very high plasma glucose (unusually high) at 125mmol when it should be 5-10
What is fractional excretion?
Amount excreted/ amount filtered
What was the difference in E1 KO mice concerning Fe% of Na?
Fe% of Na is increased = mice are not reabsorbing Na+
Fe Cl and H20 had also decreased
So losing E1 has an impact on nephron function - E1 is expressed in the PT which is really important for Na+ reabsorption
What part of the PT is E1 most likely to have a big role in and why?
Late PT as this tends to not be important for reabsorbing glucose
What is E1s role likely to be from this experiment?
Sets negative membrane potential which is important for driving forces of reabsorption through the Na+ channel
What does chromanol 293b inhibit?
KCNQ1
Why do concentrations of chromanol 293b used have to be controlled?
Too much cant be used or the heart will be affected and the animal will die
