SPAK Sensitive Regulation of the Epithelial Na Channel ENaC
Musaab Ahmed1, Madhuri S Salker, Bernat Elvira
1Department of Physiology, University of Tuebingen, Tuebingen, Germany.
The STE20/SPS1-related proline/alanine-rich kinase SPAK up-regulates the epithelial sodium channel (ENaC). This study shows SPAK enhances ENaC activity, impacting renal salt excretion and potentially hypertension.
Area of Science:
- Physiology
- Molecular Biology
- Renal Science
Background:
- The STE20/SPS1-related proline/alanine-rich kinase (SPAK) regulates salt transport, including Na(+),K(+),2Cl(-) cotransport.
- SPAK's role in regulating the epithelial Na(+) channel (ENaC) was previously unexplored.
Purpose of the Study:
- To investigate the potential of SPAK to regulate ENaC activity.
- To determine if SPAK influences renal salt excretion through ENaC modulation.
Main Methods:
- ENaC and various SPAK constructs were expressed in Xenopus oocytes.
- Amiloride-sensitive current (Iamil) was measured using dual electrode voltage clamp.
- Iamil was also assessed in colonic tissue from wild-type and SPAK-mutant mice using Ussing chambers.
Main Results:
- Coexpression of SPAK with ENaC in oocytes significantly increased Iamil.
- Constitutively active SPAK enhanced ENaC activity, while WNK-insensitive or catalytically inactive mutants did not.
- Colonic Iamil was significantly lower in mice with WNK-insensitive SPAK compared to wild-type mice.
Conclusions:
- SPAK positively regulates ENaC activity.
- SPAK's modulation of ENaC suggests a role in controlling renal sodium handling and blood pressure.
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