L-type calcium channel modulates cystic kidney phenotype

Abstract

In polycystic kidney disease (PKD), abnormal proliferation and genomic instability of renal epithelia have been associated with cyst formation and kidney enlargement. We recently showed that L-type calcium channel (Cav1.2) is localized to primary cilia of epithelial cells. Previous studies have also shown that low intracellular calcium level was associated with the hyperproliferation phenotype in the epithelial cells. However, the relationship between calcium channel and cystic kidney phenotype is largely unknown. In this study, we generated cells with somatic deficient Pkd1 or Pkd2 to examine ciliary CaV1.2 function via lentiviral knockdown or pharmacological verapamil inhibition. Although inhibition of CaV1.2 expression or function did not change division and growth patterns in wild-type epithelium, it led to hyperproliferation and polyploidy in mutant cells. Lack of CaV1.2 in Pkd mutant cells also decreased the intracellular calcium level. This contributed to a decrease in CaM kinase activity, which played a significant role in regulating Akt and Erk signaling pathways. Consistent with our in vitro results, CaV1.2 knockdown in zebrafish and Pkd1 heterozygous mice facilitated the formation of kidney cysts. Larger cysts were developed faster in Pkd1 heterozygous mice with CaV1.2 knockdown. Overall, our findings emphasized the importance of CaV1.2 expression in kidneys with somatic Pkd mutation. We further suggest that CaV1.2 could serve as a modifier gene to cystic kidney phenotype.

Vasopressin and disruption of calcium signalling in polycystic kidney disease

“…Yamaguchi et al showed that inhibition of calcium-dependent phosphatidylinositol 3-kinase activity and downstream inhibition of Akt in mouse collecting duct epithelial cells allows B rapidly accelerated fibrosarcoma (B-Raf) and ERK to be activated in a PKA-, Src-, and Ras-dependent manner and underlie the proliferative response to cAMP in the setting of reduced calcium. 119 Consistent with these observations other studies have shown that knockdown of PC1 or PC2, reduction in intracellular calcium and downregulation of calcium calmodulin kinase II (CaMKII) inhibit Akt and activate ERK, 137,138 and that knockdown of CaMKII induces pronephric cysts in zebrafish. 139 Similarly, inhibition of PKA-associated proliferation by elevation of intracellular calcium in cholangiocytes derived from PCK rats has been shown to be dependent on the activation of PI3K and Akt.…”

“…This view is supported by an increasing number of in vivo studies that have focused on the ability of calcium aimed interventions to modify the course of PKD as summarized in Table 2. 38,167–171,138,172–176 …”

“…The administration of verapamil aggravated cyst development in Cy/+ Han:SPRD rats._ENREF_134 169 CaV1.2 zebrafish morphants have dilated pronephric ducts. 138 Lentiviral transfection of CaV1.2 shRNA aggravates the cystic phenotype in Pkd1 +/− mice. 138 …”

A role for primary cilia in aortic valve development and disease

“…Motile cilia (hundreds per cell) are primarily involved in fluid movements. In contrast, immotile cilia (or primary cilia) are solitary (one per cell); extend from the anchoring basal body; and function as cellular "antennae" to coordinate various signaling pathways (Ishikawa and Marshall, 2011) such as Notch1 (Liu et al, 2007;Samsa et al, 2015;Grisanti et al, 2016;Li et al, 2016), Hedgehog (Echelard et al, 1993), Wnt (Lienkamp et al, 2012), Platelet-derived growth factor (Pdgf) (Schneider et al, 2005;Clement et al, 2013b), and TGFß (Clement et al, 2013a), as well as calcium sinks (Delling et al, 2013) and potentially as mechanosensors on endothelial cells (Jin et al, 2014). Although primary cilia have been previously linked to congenital heart malformations, such as heterotaxy and atrioventricular septal defects (Li et al, 2004;Hoffmann et al, 2009;Friedland-Little et al, 2011;Hoffmann et al, 2014;Li et al, 2015), the role of these structures in the aortic valves is unknown.…”

Calcium channels in primary cilia

“…Nauli's laboratory has recently shown that the L-type calcium channel modulates cystic kidney phenotype, hydrocephalus, and left-right asymmetry defects (74, 75). L-type calcium channel knockdown in zebrafish facilitates the formation of these ciliopathic phenotypes.…”