Anks3 interacts with nephronophthisis proteins and is required for normal renal development

Abstract

Nephronophthisis (NPH) is a heterogenetic autosomal recessive disorder associated with kidney cysts and multiple extrarenal manifestations. The disease-associated gene products (NPHPs) typically contain domains involved in protein-protein interactions, and appear to exert their tissue-specific functions in large protein complexes. Most NPHPs localize to the cilium and/or basal body; however, their precise molecular functions remain largely unknown. We have recently identified the SAM-domain containing protein Anks3 as a potential ANKS6/NPHP16-interacting protein, and report now that Anks3 interacts with several NPHPs as well as with Bicc1 and the oxygen-sensitive asparaginyl hydroxylase HIF1AN. Knockdown of anks3 in zebrafish embryos was associated with NPH-typical manifestations, including ciliary abnormalities, cyst formation, and laterality defects. In multi-ciliated epidermal cells, GFP-tagged Anks3 localizes to the cilium, but forms large aggregates in the absence of NPHP1, indicating that the negatively charged NPHP1 curtails the polymerization of Anks3. Collectively, these findings suggest that Anks3 is a cilia-associated molecule that partners with the ANKS6- and via NPHP1 to the NPHP1-4-8 module. Thus, developmental defects associated with Anks3 depletion in zebrafish suggest that ANKS3 mutations may cause NPH or NPH-like disease in humans.

Anks3 alters the sub-cellular localization of the Nek7 kinase

“…1A, first lane). Since we previously found Nek7 in two independent mass spectrometry-based screens using Anks6 or Anks3 as baits, respectively [5,6], we examined if Nek7 also interacts with Anks6. After co-immunoprecipitation with F.Nek7, no interaction with V5-tagged rat Anks6 (V5.Anks6) was detected, implying that the Nek7 interaction with Anks6 is possibly indirect (Supplemental Fig.…”

“…We have recently identified Anks3 as a binding partner of Anks6/ NPHP16, and characterized Anks3 as a molecule associated nephronophthisis-like phenotypes in model organisms [5]. Mutations in ANKS6 were identified in six families affected by nephronophthisis, and anks6 down-regulation in zebrafish and Xenopus laevis caused cyst formation, ciliary phenotypes and situs inversus [6].…”

“…Furthermore, anks6 or anks3 depletion in zebrafish resulted in overlapping ciliary phenotypes [5]. Anks3 and Anks6 form heteromeric protein complex that interacts with the SAM domain containing RNA binding protein BICC1 [5], [6].…”

“…Anks3 and Anks6 form heteromeric protein complex that interacts with the SAM domain containing RNA binding protein BICC1 [5], [6]. While Anks6 associates only with the NPHP2-NPHP3-NPHP9 module, Anks3 preferentially binds the NPHP1-NPHP4-NPHP8 module, but also associates with the Anks6 containing NPHP2-NPHP3-NPHP9 module [5]. The Anks3 containing NPHP1-NPHP4-NPHP8 module appears to function at the transition zone of cilia and in apical organization of polarized epithelial cells [7].…”

The SAM domain of ANKS6 has different interacting partners and mutations can induce different cystic phenotypes

“…6,8 Among mutations described in human ANKS6, one patient harbored a truncation at the N-terminal end of the SAM domain, suggesting an important role of this domain also in ANKS6 function in humans.…”