Lipid rafts are required for effective renal D₁dopamine receptor function

Abstract

contributed equally and are considered as co-first authors. AbstractEffective receptor signaling is anchored on the preferential localization of the receptor in lipid rafts, which are plasma membrane platforms replete with cholesterol and sphingolipids. We hypothesized that the dopamine D 1 receptor (D 1 R) contains structural features that allow it to reside in lipid rafts for its activity. Mutation of C347 palmitoylation site and Y218 of a newly identified Cholesterol Recognition Amino Acid Consensus motif resulted in the exclusion of D 1 R from lipid rafts, blunted cAMP response, impaired sodium transport, and increased oxidative stress in renal proximal tubule cells (RPTCs). Kidney-restricted silencing of Drd1 in C57BL/6J mice increased blood pressure (BP) that was normalized by renal tubule-restricted rescue with D 1 R-wild-type but not the mutant D 1 R 347A that lacks a palmitoylation site. Kidney-restricted disruption of lipid rafts by β-MCD jettisoned the D 1 R from the brush border, decreased sodium excretion, and increased oxidative stress and BP in C57BL/6J mice. Deletion of the PX domain of the novel D 1 R-binding partner sorting nexin 19 (SNX19) resulted in D 1 R partitioning solely to non-raft domains, while silencing of SNX19 impaired D 1 R function in RPTCs. Kidney-restricted silencing of 7000 | TIU eT al.

Lipid Rafts and Dopamine Receptor Signaling

“…Lipid rafts are important in organizing signal transduction cascades [ 1 , 2 , 6 , 7 , 8 , 9 , 12 , 15 , 16 , 65 , 66 ]. D 1 R partitions to lipid as well as non-lipid rafts in human renal proximal tubule cells expressing wild-type GRK4 [ 67 , 68 , 69 , 70 ] and interacts with the lipid raft protein Cav1 [ 67 , 68 , 71 , 72 , 73 , 74 , 75 ] in renal proximal tubule cells. Additionally, it interacts Cav2 in HEK293 cells expressing D 1 R [ 76 ].…”

“…SNX5 is important in the recycling of glycosylated D 1 R to the plasma membrane that requires the di-leucine motif (L344–L345) at the D 1 R C-terminus [ 8 ]. The mutation of two specific palmitoylation sites (C347 and Y218) of a CRAC motif resulted in the absence of D 1 R in lipid rafts [ 70 ]. Some of the recycled D 1 R has to be targeted to lipid rafts to be functional; this is not afforded by SNX5, probably because it is mainly expressed in non-lipid rafts.…”

“…Some of the recycled D 1 R has to be targeted to lipid rafts to be functional; this is not afforded by SNX5, probably because it is mainly expressed in non-lipid rafts. The recycling of D 1 R to lipid rafts is probably due to SNX19, which is normally exclusively found in the lipid raft [ 70 ]. For D 1 R to function, a critical amount of D 1 R has to be inserted in lipid rafts where adenylyl cyclase 6 is expressed; adenylyl cyclase 6 is activated to a greater extent by D 1 R than D 5 R [ 67 ].…”

“…siRNA-mediated silencing of SNX19 in human renal proximal tubule cells impairs the ability of the D 1 R/D 5 R agonist fenoldopam to inhibit renal sodium transport. Renal-restricted siRNA-mediated depletion of SNX19 in mice decreases D 1 R expression and increases oxidative stress and blood pressure [ 70 , 94 ]. Lipid raft bestows protection against oxidative stress by maintaining NOX (NADPH oxidase) in the inactive state in human renal proximal tubule cells [ 68 ], the opposite of what is observed in normotensive rat renal proximal tubule cells [ 87 ], thus the need for caution in extrapolating non-human studies to human physiology, pathophysiology, or pharmacology.…”

“…Interestingly, SNX1 −/− mice have increased oxidative stress; oxidative stress being the cause or effect of hypertension [ 16 , 18 , 19 , 96 , 97 ]. D 1 R and D 5 R dysfunction or deficiency increases blood pressure, in part by an increase in oxidative stress [ 3 , 4 , 5 , 16 , 18 , 19 , 70 , 97 , 98 , 99 ].…”