Date Published: May 6, 2019
Publisher: Public Library of Science
Author(s): Parama Paul, Sreekumar Ramachandran, Sheng Xia, Jay R. Unruh, Juliana Conkright-Fincham, Rong Li, Maria Fragiadaki.
Autosomal dominant polycystic kidney disease (ADPKD) is caused mostly by mutations in polycystin-1 or polycystin-2. Fluid flow leads to polycystin-dependent calcium influx and nuclear export of histone deacetylase 5 (HDAC5), which facilitates the maintenance of renal epithelial architecture by de-repression of MEF2C target genes. Here, we screened a small-molecule library to find drugs that promotes nuclear export of HDAC5. We found that dopamine receptor antagonists, domperidone and loxapine succinate, stimulate export of HDAC5, even in Pkd1–/–cells. Domperidone targets Drd3 receptor to modulate the phosphorylation of HDAC5. Domperidone treatment increases HDAC5 phosphorylation likely by reducing protein phosphatase 2A (PP2A) activity, thus shifting the equilibrium towards HDAC5-P and export from the nucleus. Treating Pkd1–/–mice with domperidone showed significantly reduced cystic growth and cell proliferation. Further, treated mice displayed a reduction in glomerular cyst and increased body weight and activity. These results suggest that HDAC5 nucleocytoplasmic shuttling may be modulated to impede disease progression in ADPKD and uncovers an unexpected role for a class of dopamine receptors in renal epithelial morphogenesis.
ADPKD is one of the most common and life-threatening genetic diseases leading to end-stage renal failure, yet to date there are few therapeutic interventions against this disease. Most cases of ADPKD are caused by heterozygous germline mutations in either the Pkd1 or Pkd2 gene . Pkd1 encodes for polycystin-1 (PC1) protein and Pkd2 encodes for polycystin-2 (PC2) protein. PC1 and PC2 interact via their C-terminal tails to form a receptor-calcium channel complex, which some have proposed to sense mechanical stress exerted on renal epithelial cells [2–4]. Mouse with homozygous deletion of Pkd1 die in utero between embryonic day 14.4–15.5 (. Mouse models of conditional Pkd1 gene disruption showed that loss of Pkd1 at 14 days after birth does not cause immediate polycystic phenotype. Renal injury drastically accelerates cyst formation, suggesting that polycystins either play a protective role against stress-induced injury or orchestrate proper repair of damaged tissue. Cystic growth is driven by a combination of abnormal proliferation of cyst lining cells and transepithelial fluid secretion into cyst lumen, a process driven by intracellular 3′, 5′- cyclic adenosine monophosphate (cAMP) via apical cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel [6–11]. Thus, a potential avenue for treating ADPKD may reside in therapeutic restoration of the protective functions disrupted by polycystin mutations.
Class IIa HDACs confer transcriptional repression through recruitment of co-repressors and other histone-modifying enzymes such as Class I HDACs [51–53]. The interaction between class IIa HDACs and MEF2 family transcription factors is a common target of mechanosensory pathways in cardiac myocytes , blood vessels  and renal tubule cells . The results described in this study in combination with previous work demonstrate that HDAC5, a class IIa HDAC, is a target of polycystin-mediated fluid sheer stress sensation and plays a role in cyst formation and the development of ADPKD. Genetic inhibition of HDAC5, even heterozygosity, can suppress cyst formation caused by the Pkd1 mutation, providing the genetic basis supporting HDAC5 as a therapeutic target for ADPKD disease intervention. However, because HDAC5, like other class IIa HDAC members, lacks intrinsic histone deacetylase activity, the conventional approach of screening for enzymatic inhibitors is unlikely to be fruitful. Our screen design took advantage of the knowledge that the nucleo-cytoplasmic shuttling of HDAC5 regulates its activity as a transcriptional repressor [17, 55, 56] and was aimed at targeting the signaling network that regulates HDAC5. Unexpectedly, our screen revealed that dopamine antagonists cause the nuclear export of HDAC5 in a PKD1- and cilia-independent manner. Loxapine succinate is a FDA approved antipsychotic drug. Domperidone was previously approved by FDA but was recently removed from the market in the US because of its potential harmful effect on children when it is used for increasing lactation by increasing prolactin levels and its association with risk of cardiac arrhythmia in older patients. Nevertheless, domperidone is a well-accepted drug for treating severe nausea and gastric reflux and is widely used in Canada and Europe .