Ammonia metabolism is critical for normal health. Inappropriate ammonia metabolism in the kidney leads to metabolic acidosis and in the liver leads to ammonia encephalopathy. In the central nervous system increased extracellular ammonia alters neuronal function and can lead to encephalopathy. Accordingly, understanding the cellular and molecular mechanisms of ammonia metabolism, which includes ammonia transport, is important. Recent studies have identified a novel family of ammonium ion (NH4+)-specific transporters. These proteins were first identified in yeast and in plants, and homologues are present throughout nature. In model systems, such as yeast, plants and bacteria, these are intrinsic membrane proteins that mediate high-affinity, ammonium-specific transport and whose expression is physiologically regulated. Two of these proteins, RhBG and RhCG are expressed in the connecting segment and the collecting duct of the kidney, and exhibit polarized expression. These observations lead us to postulate that RhBG and RhCG are integral membrane, physiologically-regulated ammonium-ion transporters that play critical roles in renal ammonia metabolism. The broad, long-term objectives of this project are to define the roles of RhBG and RhCG in mammalian renal physiology. To do so, the Specific Aims of the current proposal are to: (1) Define the regulation of mouse renal RhBG and RhCG expression and vesicular trafficking in response to specific clinical conditions associated with altered renal ammonia metabolism; (2) Determine the mechanism of extracellular ammonia-stimulated changes in RhBG- and RhCG-mediated ion transport; and, (3) identify the specific ion-transport characteristics of RhBG and RhCG. We will utilize in vivo animal models of altered renal ammonia metabolism, metabolic acidosis and alkalosis and hypokalemia, to define the regulation of RhBG and RhCG expression and cellular localization, a cultured collecting duct cell line, mIMCD-3, for in vitro studies examining the cellular mechanisms underlying regulation of RhBG and RhCG-mediated transport, and heterologous expression systems in which to define the specific ion transport characteristics of RhBG and RhCG.
| 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 |
| Harris, Autumn N; Lee, Hyun-Wook; Osis, Gunars et al. (2018) Differences in renal ammonia metabolism in male and female kidney. Am J Physiol Renal Physiol 315:F211-F222 |
| Lee, Hyun-Wook; Osis, Gunars; Harris, Autumn N et al. (2018) NBCe1-A Regulates Proximal Tubule Ammonia Metabolism under Basal Conditions and in Response to Metabolic Acidosis. J Am Soc Nephrol 29:1182-1197 |
| Lee, Hyun-Wook; Osis, Gunars; Handlogten, Mary E et al. (2017) Proximal tubule glutamine synthetase expression is necessary for the normal response to dietary protein restriction. Am J Physiol Renal Physiol 313:F116-F125 |
| Weiner, I David; Verlander, Jill W (2017) Ammonia Transporters and Their Role in Acid-Base Balance. Physiol Rev 97:465-494 |
| Lee, Hyun-Wook; Handlogten, Mary E; Osis, Gunars et al. (2017) Expression of sodium-dependent dicarboxylate transporter 1 (NaDC1/SLC13A2) in normal and neoplastic human kidney. Am J Physiol Renal Physiol 312:F427-F435 |
| Weiner, I David (2017) Roles of renal ammonia metabolism other than in acid-base homeostasis. Pediatr Nephrol 32:933-942 |
| Canales, Benjamin K; Smith, Jennifer A; Weiner, I David et al. (2017) Polymorphisms in Renal Ammonia Metabolism Genes Correlate With 24-Hour Urine pH. Kidney Int Rep 2:1111-1121 |
| Osis, Gunars; Handlogten, Mary E; Lee, Hyun-Wook et al. (2016) Effect of NBCe1 deletion on renal citrate and 2-oxoglutarate handling. Physiol Rep 4: |
| Lee, Hyun-Wook; Osis, Gunars; Handlogten, Mary E et al. (2016) Proximal tubule-specific glutamine synthetase deletion alters basal and acidosis-stimulated ammonia metabolism. Am J Physiol Renal Physiol 310:F1229-42 |
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