Abstract FR594: Distal-tubule-specific enhancement of ATRAP suppresses angiotensin II-induced hypertension

Background: The renal tubular RAS, through AT1R signaling, plays a central role in promoting sodium reabsorption, hypertension, and target-organ damage. Sodium transporters such as the NCC and ENaC are known to be regulated downstream of this pathway. However, the detailed molecular mechanisms controlling their expression and activity remain incompletely understood. ATRAP (AT1R-associated protein) is an endogenous modulator that inhibits pathological AT1R signaling. We have shown that dysregulation of renal ATRAP causes hypertension under various pathological conditions (Hypertension 2013; J Am Heart Assoc 2015; Kidney Int 2014, 2017, 2022; J Biol Chem 2023). Hypothesis: ATRAP in the distal tubule acts as a segment-specific brake on pathological RAS activation, suppressing angiotensin II–induced elevation in blood pressure via inhibition of NCC and ENaC. Methods: Distal-tubule-specific ATRAP transgenic mice (DT-ATRAP TGM) were generated by microinjecting V5-tagged ATRAP cDNA under the Ksp-cadherin promoter into C57BL/6 zygotes. Segment-specific overexpression was confirmed by immunostaining with nephron markers (megalin, calbindin, AQP2). Blood pressure responses to chronic angiotensin II infusion were compared between DT-ATRAP TGM and wild-type littermates. To further dissect the molecular basis of sodium transporter regulation, AT1R was stably expressed in mouse distal convoluted tubule (mDCT) cells. Cells were stimulated with angiotensin II, and transcriptomic changes were assessed via mRNA sequencing. Inhibitor experiments were conducted to delineate the signaling pathways downstream of AT1R–ATRAP interaction. Results: Among six founder lines, the selected DT-ATRAP TGM line exhibited >10-fold renal ATRAP expression, specifically in the distal convoluted and connecting tubules. Angiotensin II infusion led to marked blood pressure elevation in wild-type mice, whereas DT-ATRAP TGM showed significantly blunted hypertensive responses. Conclusion and Future Directions: Our in vivo and in vitro data together support that ATRAP in the distal nephron protects against angiotensin II–induced hypertension, likely by restraining NCC and ENaC. Transcriptomic profiling of mDCT cells suggests that ATRAP modulates key signaling cascades at the transcriptional level. A more comprehensive understanding of ATRAP-mediated transcriptional regulation of sodium transporters may uncover new therapeutic strategies targeting segment-specific intrarenal RAS control in hypertension.