cAMP signalling and phosphodiesterase activity in cystogenesis of autosomal dominant polycystic kidney disease

Thesis

ADPKD affects 12 million people worldwide.(Igarashi and Somlo 2002) Characterised by the formation of fluid-filled kidney cysts, it is the fourth most common cause of end-stage renal disease. Yet, there is currently no cure for this disease. Tolvaptan, a V2R antagonist which blocks GPCR signalling, proved robust in clinical trials, but was also associated with numerous adverse side effects such as polyuria, nocturia, polydipsia, thirst, as well as hepatotoxicity.(Blair 2019) These collateral symptoms beg for the development of a better therapy for ADPKD. Enhanced cAMP signalling in the primary cilium of ADPKD cells drives cystogenesis, but thanks to the strict compartmentalisation of this second messenger, there is evidence to suggest the same cyclic nucleotide mitigates cyst formation when signalling from a domain in the cell body.(Hansen, Kaiser, Leyendecker, Stüven, Krause, Derakhshandeh, Irfan, Sroka, Preval, and Desai 2022) Thus, identifying these distinguished pools of cystprotective cAMP would lead towards better treatment for ADPKD. Here, we set out to discover these domains of cAMP which reduce cystogenesis in vitro, and to identify the enzymes which regulate this second messenger at these locales. We provide evidence that in vitro inhibition of Phosphodiesterase 3 (PDE3), an enzyme which breaks down cAMP at the plasma membrane, ER, and Outer Mitochondrial Membrane, leads to mitigated cyst formation in vitro. PDE3 inhibition also decreased ER-mitochondrial contact sites in a renal cell line. The findings are consistent with a model where PDE3 alters organelle interaction and subsequent cystogenesis through a direct interaction with Polycystin 2 (PC2), one of the proteins mutated in 15% of ADPKD cases. Targeting PDE3, thus manipulating a cystprotective nanodomain of second messenger, could be a selective therapeutic strategy for alleviating renal cystogenesis with minimal side effects.

Authors: Paolocci, E

• DOI: 10.5287/ora-yxoyzxa17
• Type of award: DPhil
• Awarding institution: University of Oxford
• Language: English
• Keywords: cAMP signaling; FRET microscopy; primary cilia; autosomal dominant polycystic kidney disease; phosphodiesterases; ER-Mitochondrial Contact Sites
• Subjects: cAMP signaling; Autosomal Dominant Polycystic Kidney Disease