Polycystin-2 and phosphodiesterase 4C are components of a ciliary A-kinase anchoring protein complex that is disrupted in cystic kidney diseases

Abstract

Polycystic kidney disease (PKD) is a genetic disorder that is characterized by cyst formation in kidney tubules. PKD arises from abnormalities of the primary cilium, a sensory organelle located on the cell surface. Here, we show that the primary cilium of renal epithelial cells contains a protein complex comprising adenylyl cyclase 5/6 (AC5/6), A-kinase anchoring protein 150 (AKAP150), and protein kinase A. Loss of primary cilia caused by deletion of Kif3a results in activation of AC5 and increased cAMP levels. Polycystin-2 (PC2), a ciliary calcium channel that is mutated in human PKD, interacts with AC5/6 through its C terminus. Deletion of PC2 increases cAMP levels, which can be corrected by reexpression of wild-type PC2 but not by a mutant lacking calcium channel activity. Phosphodiesterase 4C (PDE4C), which catabolizes cAMP, is also located in renal primary cilia and interacts with the AKAP150 complex. Expression of PDE4C is regulated by the transcription factor hepatocyte nuclear factor-1β (HNF-1β), mutations of which produce kidney cysts. PDE4C is down-regulated and cAMP levels are increased in HNF-1β mutant kidney cells and mice. Collectively, these findings identify PC2 and PDE4C as unique components of an AKAP complex in primary cilia and reveal a common mechanism for dysregulation of cAMP signaling in cystic kidney diseases arising from different gene mutations.

International Union of Basic and Clinical Pharmacology. CI. Structures and Small Molecule Modulators of Mammalian Adenylyl Cyclases

“…AVP-cAMP signaling within primary cilium directly regulates cyst growth in autosomal dominant polycystic kidney disease, the most common genetic cause of kidney failure (Rieg and Kohan, 2014). In a mouse model of polycystic kidney disease, loss of AC6 markedly reduced cyst formation and renal injury (Rees et al, 2014), consistent with AC6 association with an AKAP-scaffolded complex containing polycystin-2 in primary cilium (Choi et al, 2011). The localization of AC6 in osteocyte cilia likely contributes to its role in loading-induced bone adaptation (Lee et al, 2014).…”

Strategies Targeting cAMP Signaling in the Treatment of Polycystic Kidney Disease

“…33,40 (2) Dysfunction occurs in a ciliary protein complex (comprising A-kinase anchoring protein 150, AC5/6, polycystin-2, PDE4C, and protein kinase A [PKA]), where polycystin-2-mediated calcium entry inhibits AC5/6 and activates PDE4C. 41 (3) (1) Reduced calcium activates calcium-inhibitable AC6, directly inhibits calcium/calmodulin-dependent PDE1 (by also increasing the levels of cGMP), and indirectly inhibits cGMP-inhibitable PDE3. (2) Dysfunction occurs in a ciliary protein complex (comprising A-kinase anchoring protein 150, AC5/6, polycystin-2, PDE4C, and PKA), which normally restrains cAMP signaling through inhibition of AC5/6 activity by polycystin-2-mediated calcium entry and degradation of cAMP by PDE4C transcriptionally controlled by HNF1b.…”

Phosphodiesterase Isoform Regulation of Cell Proliferation and Fluid Secretion in Autosomal Dominant Polycystic Kidney Disease

“…to increased cAMP levels. 35 We found AKAP79 was part of a signaling complex with PDE1 and B-Baf and an elevation in cAMP increased the association of these proteins in ADPKD cells, but not NHK cells (Figures 7 and 8). These data provide an explanation for how PDE1 could be the central isoform involved in the regulation of cAMP within membrane domains involved in B-Raf/MEK/ERK activation and cell proliferation.…”

“…33,34 AKAP79 has been shown to interact with components of the cAMP pathway, including AC5/6, PKA, and PDE4C and PC2, in primary cilia of renal cells. 35 In the absence of AVP or cAMP, AKAP79 and B-Raf were not appreciably bound in either ADPKD or NHK cells ( Figure 8, Supplemental Figure 4). After AVP or cAMP treatment, AKAP79 and B-Raf associated significantly in ADPKD cells, but not in NHK cells.…”