The Na+/K+-ATPase β1 Subunit is a Kidney ADP-Ribosyl Cyclase
Tae-Sik Nam1, Seong-Kyu Choe2,3, Uh-Hyun Kim1
1Department of Biochemistry, Wonkwang University, Iksan, Korea.
Summary
The kidney's Na, K-ATPase β1 subunit (Atp1b1) acts as an ADP-ribosyl cyclase (ARC), producing cyclic ADP-ribose (cADPR). This enzyme mediates calcium signaling in response to angiotensin II.
Area of Science:
- Biochemistry
- Cellular Biology
- Physiology
Background:
- ADP-ribosyl cyclase (ARC) synthesizes cyclic ADP-ribose (cADPR), a crucial second messenger for calcium (Ca2+) mobilization.
- The precise identity and function of ARC in kidney physiology, particularly in response to hormonal stimuli like angiotensin II (AngII), remain incompletely understood.
Purpose of the Study:
- To identify and characterize the ADP-ribosyl cyclase (ARC) involved in AngII-mediated signaling in the kidney.
- To elucidate the role of the identified ARC in regulating intracellular Ca2+ levels and downstream signaling pathways.
Main Methods:
- Purification of ARC activity from rat kidney tissue.
- Biochemical assays to confirm recombinant Atp1b1's ARC activity and cADPR production.
- Gene knockdown of Atp1b1 in mouse mesangial cells (MES-13) followed by AngII stimulation and Ca2+ imaging.
Main Results:
- The β1 subunit of Na, K-ATPase (Atp1b1) was identified as the primary ARC in rat kidney extracts.
- Recombinant Atp1b1 demonstrated potent ARC activity, efficiently generating cADPR from NAD.
- Knockdown of Atp1b1 in MES-13 cells significantly attenuated AngII-induced cADPR synthesis and prolonged Ca2+ signaling.
Conclusions:
- Atp1b1 functions as a key ADP-ribosyl cyclase in kidney cells.
- Atp1b1 is directly involved in mediating AngII-induced Ca2+ signaling through cADPR production.
- These findings reveal a novel role for Atp1b1 in regulating renal cellular responses to hormonal stimulation.
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