Abstract 15331: Epigenetic Interaction of Grk4 and Slc4a5 Variants Regulates Gene Transcription and Blood Pressure

Salt sensitive hypertension is associated with variants of G protein-coupled receptor kinase 4γ (GRK4), as well as with activating variants of the solute carrier family 4 member 5 (rs7571842 and rs10177833; SLC4a5), which encodes the sodium bicarbonate transporter 2 (NBCe2). We tested the hypothesis that the effect of the R65L variant (rs2960306) of GRK4 (GRK4γ 65L) on salt-sensitivity involves a gene-gene interaction with SLC4a5 variants. We found that the renal expression of SLC4a5 is increased in salt sensitive transgenic mice expressing GRK4γ 65L and is higher (50%; n=4; P<0.02) than that in GRK4 γ expressing the wild type variant (WT). Moreover, that AAV9-mediated renal specific overexpression of SLC4a5 in GRK4γ 65L mice increases the blood pressure (BP) response to a high salt diet compared with mice expressing empty vector (n=3; P<0.05). We studied human renal proximal tubule cells (hRPTCs) endogenously expressing GRK4 WT and SLC4a5 WT, GRK4 65L, SLC4a5 variants and both GRK4 65L and SLC4a5 variants. SLC4A5 expression is increased in hRPTCs expressing GRK4 65L and in cells expressing both GRK4 65L and SLC4a5 variants (n=5, P<0.05) compared with GRK4 WT. GRK4 can interact with nuclear histone deacetylases (HDACs) and co-immunoprecipitates with HDAC1 in nuclear fractions of hRPTCs. Renal-selective downregulation of HDAC1 increases BP in C57Bl/6J (P<0.05) mice. hRPTCs carrying both GRK4 65L and SLC4a5 variants have decreased expression (60%; n=4; P<0.05) of HDAC1 compared with cells expressing GRK4 WT and SLC4a5 WT or GRK4 65L This correlates with increased histone H4 acetylation but unchanged H2A, H2B and H3 acetylation in cells carrying both variants. Our results indicate a complex interaction between these variants in the regulation not only of SLC4a5 expression but that of other genes involved in salt sensitivity.