Sorting nexin‐25, a novel member of the dopamine receptor signalplex, up‐regulates D ₁ and D ₂ dopamine receptor expression in HEK293 cells

Abstract

Dopamine receptors (DARs) do not exist as singular independent units within the synaptic membrane, but are part of large macromolecular complexes of interacting proteins. These interacting proteins influence the receptor in a variety of ways. Our current studies employ a co‐immunoprecipitation assay for DARs from transfected cell lines, coupled with mass spectrometry sequencing to identify interacting partners. One protein identified this way was sorting nexin‐25 (SNX25). Mammalian SNXs have been suggested to be involved in intracellular trafficking, internalization, and endosomal recycling or sorting. The physiological role of SNX25 is unknown. Using radioligand binding assays, we found that increasing the expression levels of SNX25 in HEK293 cells increased the amount of D1 and D2 receptor expressed. This increase in receptor expression was accompanied by an alteration in the subcellular distribution of the receptors as seen using confocal microscopy (D1 DAR) and intact cell binding assays (D2 DAR). SNX25 over‐expression also caused an increase in both D1 and D2 receptor‐mediated signaling in HEK293 cells. In contrast, SNX25 over‐expression does not appear to affect D1 DAR desensitization. Overall, these data suggest that SNX25 regulates the intracellular trafficking of D1 and D2 DARs. The mechanisms underlying these effects are being investigated. Supported by The NIH intramural program.

Sorting nexins: role in the regulation of blood pressure

“…SNX25 also regulates D 1 R in the kidney. Overexpression of Snx25 in HEK 293 cells heterologously expressing D 1 R and D 2 R increases the expression of D 1 R and D 2 R, activates the downstream molecules, and disturbs the endocytosis and recycling of D 2 R. Conversely, the expression of D 1 R and D 2 R is reduced in cells lacking Snx25 [83,84]. Thus, current studies show that renal D 1 R is regulated by some SNXs, specifically SNX5, SNX19, and SNX25.…”

“…In hRPTCs, SNX19 colocalizes with D 1 R in the cytoplasm and at the plasma membrane; activation of D 1 Rs with fenoldopam causes their endocytosis [80]. In the basal state, in the mouse kidney, as in hRPTCs, the colocalization between SNX19 and D 1 R is also observed at the plasma membrane of renal proximal tubules (RPTs); the intravenous infusion of fenoldopam increased the colocalization of SNX19 [83,84]. Thus, current studies show that renal D 1 R is regulated by some SNXs, specifically SNX5, SNX19, and SNX25.…”

Metabolite Genome-Wide Association Study for Indoleamine 2,3-Dioxygenase Activity Associated with Chronic Kidney Disease

“…Furthermore, it has been reported that SNX25 overexpression is associated with increased expression levels and signaling of D 1 R [ 54 ]. Another study has indicated that SNX5 depletion can result in hypertension in normotensive mice [ 55 ].…”

Lipid Rafts and Dopamine Receptor Signaling

“…SNX25 is expressed in many tissues, including the kidney [ 106 ]. The overexpression of SNX25 amplifies the expression of D 1 R and D 2 R. Additionally, it augments signaling mediated by D 2 R and disrupts the endocytosis and recycling of D 2 R [ 106 ] However, it does not affect D 1 R desensitization [ 106 , 107 ]. SNX27 is involved in D 2 R activation of G protein-gated inwardly rectifying channels in the brain [ 108 ].…”