The role of cilia in inflammasome activation and their role in polycystic kidney disease

• Applicant: Professor Dr. E. Wolfgang Kühn
• Subject Area: Nephrology
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 434201686

The main renal ciliopathies are autosomal dominant polycystic kidney disease (ADPKD) in adults and recessive nephronophthisis in children. These entities differ with respect to number and size of cysts but share interstitial inflammation and fibrosis. In ADPKD inflammation drives cyst growth and in both fibrosis causes loss of renal function and leads to end stage renal disease. Our group is working on which immunological pathways are deregulated in ADPKD and the cellular and molecular mechanisms thereof. We have found that cilia of renal tubular epithelial cells regulate renal inflammation. This is orchestrated by a ciliary complex of the kinase LKB1, together with polycystin 1 (PC1) and NPHP1, the gene products most commonly mutated in ADPKD and NPH. In a proteomic screen from kidney we identified the kinase NEK7 as an interactor of LKB1 and find that NEK7 functionally interacts with the LKB1/PC1/NPHP1 complex. NEK7 is an essential regulator of the nod-like-receptor NLRP3 and plays a crucial role in the activation of inflammasomes. These macro-complexes are part of the innate immune system, responding to danger molecules and causing caspase mediated activation of the interleukins – 1ß and -18, cell injury and inflammation. Expression screens in early ADPKD in the mouse reveal upregulation of inflammasome associated transscripts such as caspase 1 and IL-18. On the protein level activation of caspase 1 is seen in early ADPKD and is localized to early cysts. MDCK cells express all inflammasome components and reveal NEK7 dependent IL-18 release upon stimulation. We hypothesize that a ciliary complex of LKB1, PC1, NPHP1 and NEK7 regulates inflammasome activation in renal epithelial cells. The lack of PC1 leads to inflammsome activation and renal inflammation. In aim 1 we will examine the cellular and molecular mechanisms underlying ciliary inflammasome regulation. In aim 2 we will use genetic animal models to test if activation of inflammasomes through oxalate crystals will aggravate the phenotype, or if systemic inactivation of inflammasomes through ASC knock-out will ameliorate the disease. In aim 3 we will use a transgenic strategy in ADPKD in the mouse to differentiate between the role of inflammasomes in immune cells vs. renal epithelia. In aim 4 we will treat ADPKD mice with an inflammasome inhibitor to ascertain if pharmacological intervention in this pathway ameliorates the disease.

• DFG Programme: Research Grants