Familial cases of pseudohypoaldosteronism type II harboring a novel mutation in the Cullin 3 gene

Insights into the diverse mechanisms and effects of variant CUL3-induced familial hyperkalemic hypertension

Familial hyperkalemic hypertension (FHHt), also known as Pseudohypoaldosteronism type II (PHAII) or Gordon syndrome is a rare Mendelian disease classically characterized by hyperkalemia, hyperchloremic metabolic acidosis, and high systolic blood pressure. The most severe form of the disease is caused by autosomal dominant variants in CUL3 (Cullin 3), a critical subunit of the multimeric CUL3-RING ubiquitin ligase complex. The recent identification of a novel FHHt disease variant of CUL3 revealed intricacies within the underlying disease mechanism. When combined with studies on canonical CUL3 variant-induced FHHt, these findings further support CUL3's role in regulating renal electrolyte transport and maintaining systemic vascular tone. However, the pathophysiological effects of CUL3 variants are often accompanied by diverse systemic disturbances in addition to classical FHHt symptoms. Recent global proteomic analyses provide a rationale for these systemic disturbances, paving the way for future mechanistic studies to reveal how CUL3 variants dysregulate processes outside of the renovascular axis. Video Abstract.

Aldosterone defects in infants and young children with hyperkalemia: A single center retrospective study

INTRODUCTION

Hyperkalemia is a rare but severe condition in young children and usually discovered as a result of hemolysis of the blood samples taken. However, patients with defects in either aldosterone biosynthesis or function can also present with hyperkalemia- as well hyponatremia-associated, and metabolic acidosis. It is a challenge to make an accurate diagnosis of these clinical conditions. We conducted this study to investigate the clinical and genetic features of aldosterone signaling defects associated hyperkalemia in young children.

METHOD

A retrospective review was conducted at the pediatric department of the First Affiliated Hospital of Guangxi Medical University from 2012 to 2022.

RESULTS

47 patients with hyperkalemia were enrolled, of which 80.9% (n = 38) were diagnosed with primary hypoaldosteronism, including congenital adrenal hyperplasia due to 21-hydroxylase deficiency (n = 32), isolated hypoaldosteronism (n = 1) due to CYP11B2 gene mutation and Xp21 contiguous gene deletion syndrome (n = 1). Additionally, 4 patients were clinically-diagnosed with primary adrenal insufficiency. Nine patients were confirmed with aldosterone resistance, of which one child was diagnosed with pseudohypoaldosteronism (PHA) type 1 with a mutation in the NR3C2 gene and 3 children were identified with PHA type 2 due to novel mutations in either the CUL3 or KLHL3 genes. Five patients had PHA type 3 because of pathologies of either the urinary or intestinal tracts.

CONCLUSIONS

The etiologies of infants with hyperkalemia associated with aldosterone defects were mostly due to primary hypoaldosteronism. An elevated plasma aldosterone level may be a useful biomarker for the diagnosis an aldosterone functional defect in patients presented with hyperkalemia. However, a normal plasma aldosterone level does rule out an aldosterone defect in either its biosynthesis or function, especially in young infants. Molecular genetic analyses can greatly help to clarify the complexity of disorders and can be used to confirm the diagnosis.

Kelch-like protein 3 in human disease and therapy

Kelch-like protein 3 (KLHL3) is a substrate adaptor of Cullin3-RING ubiquitin ligase (CRL3), and KLHL3-CUL3 complex plays a vital role in the ubiquitination of specific substrates. Mutations and abnormal post-translational modifications of KLHL3-CUL3 affect substrate ubiquitination and may related to the pathogenesis of Gordon syndrome (GS), Primary Hyperparathyroidism (PHPT), Diabetes Mellitus (DM), Congenital Heart Disease (CHD), Pre-eclampsia (PE) and even cancers. Therefore, it is essential to understand the function and molecular mechanisms of KLHL3-CUL3 for the treatment of related diseases. In this review, we summary the structure and function of KLHL3-CUL3, the effect of KLHL3-CUL3 mutations and aberrant modifications in GS, PHPT, DM, CHD and PE. Moreover, we noted a possible role of KLHL3-CUL3 in carcinogenesis and provided ideas for targeting KLHL3-CUL3 for related disease treatment.