The kidney plays a key role in maintaining plasma [K+], with distal segments of the nephron fine-tuning K+ secretion to keep it in the normal range. We previously proposed that the renal distal convoluted tubule (DCT) plays a key role by sensing plasma [K+]. Decreasing plasma [K+] by dietary K+ restriction activates the WNK- SPAK/OSR1-NCC pathway, and increased NaCl reabsorption though NCC reduces delivery of sodium to, and possibly remodels, distal K+ secreting segments to lower K+ secretion. The disease Familial Hyperkalemic Hypertension (FHHt) is caused by increased NCC activation due to mutations in WNKs, Cullin 3 (CUL3), and KLHL3. The Cullin Ring Ligase (CRL) complex, composed of the scaffold CUL3, the substrate adaptor KLHL3, and the ligase RING, degrades WNKs. The effects of mutant CUL3, produced by skipping of exon 9 which causes internal deletion of 57 amino acids (CUL3-?9), are controversial. CUL3-?9 triggers its own degradation in vitro, and also in a mouse model of CUL3 FHHt. Thus, the prevailing model is that CUL3-?9 causes FHHt by inducing CUL3 haploinsufficiency. Our preliminary data in CUL3 heterozygote mice and a new mouse model of CUL3-?9 FHHt do not support this, and we hypothesize that CUL3-?9 exerts dominant effects to cause FHHt and dysregulate the plasma [K+] sensor. We propose that CUL3-?9 causes FHHt by a combined effect of lowering abundance of itself and of KLHL3. Our data suggest that NKCC2 activation along the thick ascending limb (TAL) may also contribute to FHHt. Finally, we previously generated kidney-specific CUL3 knockout (KO) mice, and found that they display a severe phenotype (polyuria and chronic kidney disease), with defects along multiple nephron segments. Our overall aim is to determine the mechanisms underlying CUL3-?9-mediated FHHt, and gain insight into CUL3 function in the kidney.
In Aim 1 we will determine the effects of CUL3-?9 expression and CUL3 KO specifically along DCT to determine whether CRL disruption along DCT is sufficient to cause FHHt. We will determine the effects of CRL disruption on KLHL3 in mice, since we found CUL3-?9 inappropriately degrades it in cultured cells. We will also directly test whether mice with lower abundance of CUL3 and KLHL3 develop FHHt.
In Aim 2 we will determine whether remodeling of K+-secreting segments occurs in FHHt mediated by CUL3-?9, and examine the effects of CRL disruption on NKCC2 activity. Some models suggest that CUL3-?9 leads to dramatically lower CRL activity, but data suggest this would be lethal. We propose that CUL3-?9 may exert unique effects that cause it to preferentially degrade certain CRL adaptors. Therefore, in Aim 3 we will examine effects of CUL3-?9 on other CRL adaptors and substrates in our mouse models and in primary cell culture.

Public Health Relevance

Maintenance of extracellular potassium concentration [K+] is essential for the normal function of neurons, skeletal muscle, and cardiac myocytes. Mutations in CUL3, a protein that promotes degradation of components of a pathway that senses plasma [K+], cause the disease Familial Hyperkalemic Hypertension. We will determine the roles of both normal and mutant CUL3 in the kidney in the regulation of plasma [K+] regulation, and also sodium balance and blood pressure, which may guide development of new treatments for potassium imbalance and high blood pressure.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK098141-07
Application #
10083727
Study Section
Kidney Molecular Biology and Genitourinary Organ Development (KMBD)
Program Officer
Ketchum, Christian J
Project Start
2014-04-01
Project End
2023-12-31
Budget Start
2021-01-01
Budget End
2021-12-31
Support Year
7
Fiscal Year
2021
Total Cost
Indirect Cost
Name
Oregon Health and Science University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
096997515
City
Portland
State
OR
Country
United States
Zip Code
97239
Terker, Andrew S; CastaƱeda-Bueno, Maria; Ferdaus, Mohammed Z et al. (2018) With no lysine kinase 4 modulates sodium potassium 2 chloride cotransporter activity in vivo. Am J Physiol Renal Physiol 315:F781-F790
Ferdaus, Mohammed Z; McCormick, James A (2018) Mechanisms and controversies in mutant Cul3-mediated familial hyperkalemic hypertension. Am J Physiol Renal Physiol 314:F915-F920
Saritas, Turgay; Puelles, Victor G; Su, Xiao-Tong et al. (2018) Optical Clearing in the Kidney Reveals Potassium-Mediated Tubule Remodeling. Cell Rep 25:2668-2675.e3
Nelson, Jonathan W; Ferdaus, Mohammed Z; McCormick, James A et al. (2018) Endothelial transcriptomics reveals activation of fibrosis-related pathways in hypertension. Physiol Genomics 50:104-116
Wang, Ming-Xiao; Cuevas, Catherina A; Su, Xiao-Tong et al. (2018) Potassium intake modulates the thiazide-sensitive sodium-chloride cotransporter (NCC) activity via the Kir4.1 potassium channel. Kidney Int 93:893-902
Ferdaus, Mohammed Z; Miller, Lauren N; Agbor, Larry N et al. (2017) Mutant Cullin 3 causes familial hyperkalemic hypertension via dominant effects. JCI Insight 2:
Cuevas, Catherina A; Su, Xiao-Tong; Wang, Ming-Xiao et al. (2017) Potassium Sensing by Renal Distal Tubules Requires Kir4.1. J Am Soc Nephrol 28:1814-1825
Blankenstein, K I; Borschewski, A; Labes, R et al. (2017) Calcineurin inhibitor cyclosporine A activates renal Na-K-Cl cotransporters via local and systemic mechanisms. Am J Physiol Renal Physiol 312:F489-F501
McCormick, James A; Ellison, David H (2017) Nephron Remodeling Underlies Hyperkalemia in Familial Hyperkalemic Hypertension. J Am Soc Nephrol 28:2555-2557
Borschewski, Aljona; Himmerkus, Nina; Boldt, Christin et al. (2016) Calcineurin and Sorting-Related Receptor with A-Type Repeats Interact to Regulate the Renal Na?-K?-2Cl? Cotransporter. J Am Soc Nephrol 27:107-19

Showing the most recent 10 out of 16 publications