The activity and cell surface density of Kir 1.1 (ROMK) channels are exquisitely controlled to regulate potassium secretion and sodium reabsorption in the kidney. Loss-of-function mutations lead to Bartter's syndrome, a hereditary salt-losing nephrology. Here we propose to elucidate key molecular mechanisms that operate to regulate the activity and surface density of these channels, building on our recent our discoveries. A stepwise multidisciplinary approach, combining molecular genetics, cellular biology, electrophysiology and transgenics, will be employed to answer the following questions about the regulation of channel gating and surface density: 1) how does the cytoplasmic N-terminal/COOH-terminal interface control channel gating? Our work on molecular basis of channel gating defects in Bartter's syndrome suggests that a key inter-subunit interaction site may control the energetics of channel opening.
This Aim i s designed to critically explore this idea, testing whether the interaction site controls pH-dependent channel gating, as conferred by titration of an N-terminal pH sensor. 2) How is the ROMK channel processed in the biosynthetic pathway? This Aim is designed to elucidate the structural basis and consequence of ER retention, providing a context to understand how phosphorylation by PKA/SGK and PDZ interactions regulate ROMK expression on the plasma membrane. 3) What is the molecular mechanism by which PKA/SGK phosphorylation regulates cell surface expression of ROMK? This Aim is designed to test the hypothesis that phosphorylation of serine 44 controls anterograde traffic from the ER/Golgi by abrogating an """"""""ER retention"""""""" signal. 4) How does NHERF-2 interaction with ROMK regulate cell surface expression? This Aim will test the hypothesis that PDZ-interactions stabilize ROMK expression on the plasmalemma, building on our discovery that the PDZ protein, NHERF-2, coordinates the assembly of a multimeric protein complex around ROMK and facilitates channel expression on the plasmalemma. 5) Does NHERF-2 interaction regulate ROMK expression in the CCD during potassium adaptation? In this Aim, we will use wild type and NHERF-2 knock-out mice to test whether NHERF-2 interaction with ROMK underpins physiological regulation of ROMK in potassium homeostasis. These studies represent a timely and important extension of the principal investigator's work, and should ultimately provide considerable insight into the basis of renal K handling and K homeostasis in health and disease.
| West, Crystal A; Welling, Paul A; West Jr, David A et al. (2018) Renal and colonic potassium transporters in the pregnant rat. Am J Physiol Renal Physiol 314:F251-F259 |
| Mackie, Timothy D; Kim, Bo-Young; Subramanya, Arohan R et al. (2018) The endosomal trafficking factors CORVET and ESCRT suppress plasma membrane residence of the renal outer medullary potassium channel (ROMK). J Biol Chem 293:3201-3217 |
| Welling, Paul A (2018) WNKs on the Fly. J Am Soc Nephrol 29:1347-1349 |
| Harris, Autumn N; Grimm, P Richard; Lee, Hyun-Wook et al. (2018) Mechanism of Hyperkalemia-Induced Metabolic Acidosis. J Am Soc Nephrol 29:1411-1425 |
| Grimm, P Richard; Coleman, Richard; Delpire, Eric et al. (2017) Constitutively Active SPAK Causes Hyperkalemia by Activating NCC and Remodeling Distal Tubules. J Am Soc Nephrol 28:2597-2606 |
| Welling, Paul A (2016) Roles and Regulation of Renal K Channels. Annu Rev Physiol 78:415-35 |
| Li, Xiangming; Ortega, Bernardo; Kim, Boyoung et al. (2016) A Common Signal Patch Drives AP-1 Protein-dependent Golgi Export of Inwardly Rectifying Potassium Channels. J Biol Chem 291:14963-72 |
| Wade, James B; Liu, Jie; Coleman, Richard et al. (2015) SPAK-mediated NCC regulation in response to low-K+ diet. Am J Physiol Renal Physiol 308:F923-31 |
| Grimm, P Richard; Lazo-Fernandez, Yoskaly; Delpire, Eric et al. (2015) Integrated compensatory network is activated in the absence of NCC phosphorylation. J Clin Invest 125:2136-50 |
| Kolb, Alexander R; Needham, Patrick G; Rothenberg, Cari et al. (2014) ESCRT regulates surface expression of the Kir2.1 potassium channel. Mol Biol Cell 25:276-89 |
Showing the most recent 10 out of 39 publications
