L9-B subunits Flashcards
what is an alpha subunit?
the subunit/protein which makes up the ion channe
what is a beta subunit?
subunit/integral membrane proteins with a small MW which interact with and regulate the activity of alpha subunit.
- the modify the properties of alpha subunits
Which members of the KCNE family are expressed in epithlial cells?
- KCNE1-3
What effect does KCNE1 have on KCNQ1 and how was this measured?
KCNE1 causes larger currents and enhances Q1 function
- there is changes in the gating and reaching a steady state is slower/delayed
- this was determined by 2 electrode voltage clamp techniques in xenopus oocytes expressing cRNA encoding fo Q1, or Q1 and E1 (overexpression)
what role does KCNE1 have in renal funtion?
- main role is in proximal tubule
- sets negative resting potential which creates driving force for Na and glucose to enter the cell via apical membrane
- net absorption of Na+ , Cl- and water follows
- E1 expressed in apical membrane- is there also a K+ channel on apical membrane?
What is relationship between location of E1 and Q1 on the apical membrane of the proximal tubule?
There are some places where epxression overlaps but is no direct overlap
- is there another K+ channel that E1 is regulating?
give the channels on a simple cell membrane of a proximal tubule renal cell
-apical - Na+ and Glucose pump - into cell
basolateral- Na/K+ ATPase
basolateral - K+ channel - out of cell
basolateral - glucose out of the cell
how were the mice treated in the Q1/E1 KO studies looking at kideny function?
- mice were anaesthetised and put on a heat pad
- jugular vein was cannulated - fluid replacement
- carotid artery cannulated - BPmeasurments and blood smaple - indicate depth of anaesthia and BP has effect on kidney function
- cannulate bladder - collect urine for analysis
what effects did KO E1 have on blood levels in the first exp?
KO E1
- no change in plasma [Na+] or [Cl-] (E1 doesn’t impact on animals ability to regulate Na, Cl in plasma)
- [glucose] in KOE1 animal is lower than in WT animal (problem in glucose handling at the kidney level) - but glucose levels were abnormally high (125mM, should be between 5-10mM) - confidence in paper is limited
- no significant difference in glomerular filtration rate
what is the equation for fractional excretion (FE)?
- Rate excretion/ Rate filtration
- if 100%, everything being filtrated is being excreted
what did another exp show which looked at the effects of E1 KO on the kidney?
- KOE1 - animals lose sodium - reduction in sodium reabsorption (higher FE)
- KOE1 - animals lose chloride - less CL- reabs (higher FE)
- KOE1 - animals lose glucose - less glucose reabs (higher FE)
- loss of water - higher urine flow rate - less water reabs as it follows Na and Cl (higher fluid FE)
- in this exp the plasma glucose was around 10mM which is within the normal/epxected range
- shows E1 is a subunit regulating a channel somewhere in the kidney which plays an important role helping the kidney drive NACL and glucose reabsorption
what does newest data looking at E1 KO i the kidney show?
- E1 KO there is reduced Na+, Cl- and water reabs
- BUT no difference in glucose handling/reabs like other exp showed
- different backgrounds?
- still OK comparison
what does chromanol 293B inhibit?
Q1
What happens when chromanol 293B is added to WT and E1KO cells?
- infusion of chromanol 293B into the jugular vein
- 293B turns WT values into E1 KO values (reduced Cl, Na and water reabs)
- 293B has no effect on E1 KO
- shows E1 is regulating a 293B sensitive K+ channel (not definately Q1)
if there is a lack of effect that E1 has on glucose handling what does this suggest its location is?
LATE proximal tubule
