A Mutation in γ-Adducin Impairs Autoregulation of Renal Blood Flow and Promotes the Development of Kidney Disease

Significance Statement The genes and mechanisms underlying the association between diabetes or hypertension and CKD risk are unclear. The authors identified a recessive K572Q mutation in γ -adducin ( Add3 ), which encodes a cytoskeletal protein (ADD3), in fawn-hooded hypertensive (FHH) rats—a mutation also reported in Milan normotensive (MNS) rats that develop renal disease. They demonstrated that FHH and Add3 knockout rats had impairments in the myogenic response of afferent arterioles and in renal blood flow autoregulation, which were rescued in Add3 transgenic rats. They confirmed the K572Q mutation’s role in altering the myogenic response in a genetic complementation study that involved crossing FHH and MNS rats. The work is the first to demonstrate that a mutation in ADD3 that causes renal vascular dysfunction also promotes susceptibility to kidney disease. Background The genes and mechanisms involved in the association between diabetes or hypertension and CKD risk are unclear. Previous studies have implicated a role for γ -adducin (ADD3), a cytoskeletal protein encoded by Add3 . Methods We investigated renal vascular function in vitro and in vivo and the susceptibility to CKD in rats with wild-type or mutated Add3 and in genetically modified rats with overexpression or knockout of ADD3. We also studied glomeruli and primary renal vascular smooth muscle cells isolated from these rats. Results This study identified a K572Q mutation in ADD3 in fawn-hooded hypertensive (FHH) rats—a mutation previously reported in Milan normotensive (MNS) rats that also develop kidney disease. Using molecular dynamic simulations, we found that this mutation destabilizes a critical ADD3-ACTIN binding site. A reduction of ADD3 expression in membrane fractions prepared from the kidney and renal vascular smooth muscle cells of FHH rats was associated with the disruption of the F-actin cytoskeleton. Compared with renal vascular smooth muscle cells from Add3 transgenic rats, those from FHH rats had elevated membrane expression of BK α and BK channel current. FHH and Add3 knockout rats exhibited impairments in the myogenic response of afferent arterioles and in renal blood flow autoregulation, which were rescued in Add3 transgenic rats. We confirmed these findings in a genetic complementation study that involved crossing FHH and MNS rats that share the ADD3 mutation. Add3 transgenic rats showed attenuation of proteinuria, glomerular injury, and kidney fibrosis with aging and mineralocorticoid-induced hypertension. Conclusions This is the first report that a mutation in ADD3 that alters ACTIN binding causes renal vascular dysfunction and promotes the susceptibility to kidney disease.