Targeting NKAα1/Src signaling in the mouse renal proximal tubule using lentivirus-mediated delivery of the NaKtide sequence: impact on renal function

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Activation of the basolateral Na + /K + -ATPase (NKA) is classically known for generating the Na + gradient that drives apical Na + reabsorption through Na + /H + exchange (NHE3) in the renal proximal tubule (PT). In contrast, activation of NKA receptor function triggers a redistribution of apical NHE3 that decreases transcellular Na + flux and increases diuresis. Mice with PT-targeted reduction of NKA by 70% have decreased diuresis and natriuresis, suggesting a predominant physiological impact of NKA signaling in the intact mouse. Mechanistically, studies have shown that NKA-mediated downregulation of NHE3 occurs through an NKAα1/Src kinase-dependent mechanism in PT epithelial cells, but this has not been tested in vivo. This was investigated in male and female C57Bl6 mice (12-weeks-old) injected intraperitoneally with vehicle (PBS) or a lentiviral vector designed to confer stable gene expression of either NaKtide (a peptide derived from the NKA signaling sequence that disrupts NKAα1/Src signaling) or a scrambled sequence under the control of the PT-specific SGLT2 promoter. Seven weeks post-infection, changes in water homeostasis were assessed. Urinary and fecal water excretion were measured using metabolic cages, respiratory water loss was measured as exhaled breath condensate (EBC), and systolic blood pressure (SBP) was measured via tail-cuff. NaKtide expression was confirmed by immunofluorescence in kidney cryosections. PBS or Lenti-Scramble injections did not modify urine output or SBP in mice of either sex. Compared to Lenti-Scramble, Lenti-Naktide did not modulate urine output (1.7±0.2, n=9 vs. 1.8±0.2 mL/24hr, n=9) or SBP (111.3±1.4, n=4 vs.113.9±1.3 mmHg, n=4) in males. In females, Lenti-Naktide did not modify SBP (118.0±1.1, n=4 vs. 117.0±0.9 mmHg, n=4), but it significantly decreased diuresis (1.2±0.2, n=10 vs. 1.9±0.2 mL/24hr, n=8, p<0.05). Lenti-Naktide infected females had unchanged fecal water excretion (0.6±0.1, n=4 vs. 0.6±0.1 g/24hr, n=4), but significantly increased EBC (1.3±0.2, n=4 vs. 1.0±0.4 g/24hr, n=4). Thus, decreased diuresis may be compensated by increased respiratory water loss. These results are consistent with a physiological role of NKAα1/Src receptor function in the regulation of PT function that is phenotypically significant in female mice. Future studies should investigate an alternate NKA signaling mechanism that may be predominant in PT Na + regulation in males. Supported by AHA Predoctoral fellowship #19PRE34450095, NIH DK129937, and NIH Grant P20GM103434. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

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