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

Abstract

The ankyrin repeat and sterile α motif (SAM) domain-containing six gene (Anks6) is a candidate for polycystic kidney disease (PKD). Originally identified in the PKD/Mhm(cy/+) rat model of PKD, the disease is caused by a mutation (R823W) in the SAM domain of the encoded protein. Recent studies support the etiological role of the ANKS6 SAM domain in human cystic diseases, but its function in kidney remains unknown. To investigate the role of ANKS6 in cyst formation, we screened an archive of N-ethyl-N-nitrosourea-treated mice and derived a strain carrying a missense mutation (I747N) within the SAM domain of ANKS6. This mutation is only six amino acids away from the PKD-causing mutation (R823W) in cy/+ rats. Evidence of renal cysts in these mice confirmed the crucial role of the SAM domain of ANKS6 in kidney function. Comparative phenotype analysis in cy/+ rats and our Anks6(I747N) mice further showed that the two models display noticeably different PKD phenotypes and that there is a defective interaction between ANKS6 with ANKS3 in the rat and between ANKS6 and BICC1 (bicaudal C homolog 1) in the mouse. Thus, our data demonstrate the importance of ANKS6 for kidney structure integrity and the essential mediating role of its SAM domain in the formation of protein complexes.

ANKS3 Co-Localises with ANKS6 in Mouse Renal Cilia and Is Associated with Vasopressin Signaling and Apoptosis In Vivo in Mice

“…Due to the localisation of both ANKS3 and ANKS6 to the primary cilium in the mouse kidney [ 7 ]and in Zebrafish [ 17 ], and experimental evidence ofANKS3 interaction with nephronophthisis proteins [ 4 , 17 ], we tested the effects of in vivo Anks3 knock down on renal expression of genes encoding proteins present in the basal body ( Cep290 , Nphp5 ) and the transition zone ( Nphp1 , Nphp2 , Nphp4 ) of the primary cilium, and in the ciliary axoneme ( Nek8 , Gli2 ) [ 18 , 19 ]( S3 Fig ). Four days after the last injection of LNA ASO, Nek8 mRNA level was increased in kidney of ANKS3 ASO treated mice, but this effect was statistically significant only when compared to SCR ASO controls.…”

“…Overexpression of transgenic Anks6 (pR823W) in the renal tubular epithelium leads to the development of cystic lesions in the kidney that are largely similar to those described in PKD/Mhm( cy /+) rats [ 3 ]. Recent results from genetic studies of ANKS6 in humans and Anks6 gene targeting in model species further underlined the important role of the protein in renal function and cystogenesis [ 4 – 7 ].…”

“…Even though the presence of these domains suggests a function of ANKS6 in protein binding and scaffolding, identification of interacting partners is essential to integrate the protein in functional networks and understand its biological roles. This line of research has been initiated with the detection of interactions between ANKS6 and the RNA binding protein BICC1, which have shed light on BICC1 mediated mechanisms (cell polarity, cAMP signaling, cilia orientation and cilia-driven-fluid flow) that may be involved in renal cystogenesis when interaction between BICC1 and ANKS6 is affected [ 7 – 9 ]. More recently, localisation of ANKS6 to the primary cilium and interactions between ANKS6 and proteins involved in nephronophthisis (INVS, NHPH3, NEK8) were demonstrated [ 4 , 6 , 7 ].…”

“…This line of research has been initiated with the detection of interactions between ANKS6 and the RNA binding protein BICC1, which have shed light on BICC1 mediated mechanisms (cell polarity, cAMP signaling, cilia orientation and cilia-driven-fluid flow) that may be involved in renal cystogenesis when interaction between BICC1 and ANKS6 is affected [ 7 – 9 ]. More recently, localisation of ANKS6 to the primary cilium and interactions between ANKS6 and proteins involved in nephronophthisis (INVS, NHPH3, NEK8) were demonstrated [ 4 , 6 , 7 ]. Protein structure analyses identified the Ankyrin repeats and sterile alpha motif domain containing 3 (ANKS3) as a potential direct binding partner of ANKS6 and provided crystal structures showing that the R823W mutation in ANKS6 destabilizes its SAM domain and prevents ANKS3-ANKS6 interaction [ 10 ].…”

Effect of Advanced Glycation End-Products (AGE) Lowering Drug ALT-711 on Biochemical, Vascular, and Bone Parameters in a Rat Model of CKD-MBD

“…The animals have a mutation in Anks6 , a gene that codes for the protein SamCystin located at the base of cilia. Although specific function is not fully elucidated, Anks6 binds with Anks3 and Bicc1 and thus may alter the nephronophthisis complex, but the cilia are not directly affected. In this rat model, CKD‐MBD develops spontaneously, with a much faster progression to end‐stage disease in male animals by 30 to 40 weeks of age, whereas female rats do not develop azotemia even as old as 21 months, or after oophorectomy .…”