Abstract: TH-OR55
Kir5.1 Is Essential to Formation of Kir4.2/Kir5.1 Heterotetramer in the Basolateral Membrane of Mouse Proximal Tubules
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Back to the Basics
October 24, 2024 | Location: Room 4, Convention Center
Abstract Time: 04:30 PM - 04:40 PM
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1101 Fluid, Electrolyte, and Acid-Base Disorders: Basic
Author
- Wang, Wen-Hui, New York Medical College School of Medicine, Valhalla, New York, United States
Background
Kir5.1 is encoded by Kcnj16 in the mouse kidney and it is expressed in the basolateral membrane of the proximal tubule (PT), distal-convoluted-tubule (DCT) and cortical- collecting-duct. In DCT, Kir5.1 interacts with Kir4.1 to form a 40-pS K+ channel, a main type of K+ channel in the basolateral membrane. Moreover, Kir4.1 can also form a homotetramer in the absence of Kir5.1 and provides the basolateral K+ conductance of DCT. In PT, Kir5.1 interacts with Kir4.2 to form Kir4.2/Kir5.1 heterotetramer, a main type basolateral K+ channel. However, it is not clear whether Kir4.2 along is sufficient for forming a Kir4.2 homotetramer without Kir5.1 in the basolateral membrane and maintains PT membrane conductancel.
Methods
We now conduct immunofluorescence-staining and patch-clamp-experiments in Kir5.1-knockout (KO) mice and corresponding wild-type (WT) mice to examine the expression of Kir4.2 and to determine the basolateral K+ channel activity and PT membrane potential.
Results
The single-channel-recording identified a 50-pS K+-channel in the basolateral membrane of PT of WT mice. This 50-pS K+-channel is a main type basolateral K+ channel and is most likely Kir4.2/Kir5.1 heterotetramer. However, this 50-pS inwardly-rectifying-K+-channel was completely absent in the PT of Kir5.1-KO mice. Moreover, patch-clamp-experiments failed to detect additional basolateral K+ channels in the PT of Kir5.1-KO mice. Immunofluorescence-staining shows that Kir4.2 is exclusively expressed in the PT. While the basolateral membrane staining of Kir4.2 was clearly visible in WT mice, it was largely absent in Kir5.1-KO mice. This is in sharp contrast to Kir4.1, which has a clear basolateral membrane staining in both WT and Kir5.1-KO mice. Also, the membrane potential of PT was more positive in Kir5.1-KO mice than WT mice, suggesting that deletion of Kir5.1 impairs Kir4.2 membrane expression. Immunoblotting also showed that the expression of Kir4.2 and Na/H exchanger-3 was lower in Kir5.1-KO mice than WT mice.
Conclusion
We conclude that Kir5.1 is essential for forming the basolateral 50-pS K+-channel in the PT and plays a role in determining Kir4.2 basolateral membrane abundance. Also, Kir4.2 could not form a homeotetrammer in the absence of Kir5.1 and the membrane potential of PT is depolarized in the Kir5.1-KO mice.
Funding
- NIDDK Support