This is a twice-amended R01 renewal application, the purpose of which is to study the molecular mechanisms of the rapid regulation of the type-1 sodium-proton exchanger, NHE-1 (also known as product of SLC9A1, solute carrier family 9A, type 1). NHE-1 is ubiquitous, being expressed on the plasma membrane of virtually every mammalian cell. It mediates the 1:1 exchange of extracellular Na+ for intracellular H+, thereby maintaining intracellular pH. NHE-1 also plays cell-specific roles in cell volume maintenance, mitogenesis, cell- cycle regulation, apoptosis and a host of other cellular functions. NHE-1 has also been implicated in clinically relevant conditions such as hypertension, left ventricular hypertrophy, and ischemia-reperfusion injury. Despite its ubiquitous expression in mammalian cells and its potential clinical relevance, much remains to be learned regarding the molecular mechanisms through which this important protein is regulated. We seek a better understanding of the mechanisms through which NHE-1 is activated. We propose a model based on the idea that phosphorylation of NHE-1 and binding of CaM to NHE-1, disrupt electrostatic tethers that occlude the proton sensing and transport regions of NHE-1 in its basal state. Disruption of the tethers allows access of ambient protons to the proton sensing and transport regions of NHE-1, thus resulting in its activation. The activation is potentially facilitated by CA-II, which could couple to NHE-1 in a "metabolon", and which could gain access to the proton sensing and transport regions of NHE-1 by sliding into a pocket created when the electrostatic tethers are disrupted. This model will be tested in three specific aims:
Aim #1 : We will examine the role of Jak2-induced tyrosine phosphorylation of CaM in the activation of NHE-1.
Aim #2 : We will examine the role of carbonic anhydrase type 2 (CA-II) as a key regulatory protein that increases the activity of NHE-1.
Aim #3 : We will examine the role of electrostatic interactions involving the carboxyl terminus of NHE-1 in its activation. We believe that the proposal has been significantly improved by focusing on evaluating this potentially unifying mechanism of activation of NHE-1, which is a natural outgrowth of our previous work in this area, and which could serve as the foundation for the development of a molecular model for the activation of NHE-1. This proposal could also lay the foundation for future structural experiments utilizing NMR and/or crystallography methods.

Public Health Relevance

This project is relevant to public health in that NHE-1 is involved in the regulation of blood pressure, kidney function and heart muscle contraction. The work could lead to new therapies for hypertension, congestive heart failure, cardiomyopathies and kidney failure.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
Project #
Application #
Study Section
Cellular and Molecular Biology of the Kidney Study Section (CMBK)
Program Officer
Ketchum, Christian J
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Medical College of Wisconsin
Internal Medicine/Medicine
Schools of Medicine
United States
Zip Code
Coaxum, Sonya D; Blanton, Mary G; Joyner, Alisha et al. (2014) Epidermal growth factor-induced proliferation of collecting duct cells from Oak Ridge polycystic kidney mice involves activation of Na+/H+ exchanger. Am J Physiol Cell Physiol 307:C554-60
Dey, Mamon; Baldys, Aleksander; Sumter, Dezmond B et al. (2010) Bradykinin decreases podocyte permeability through ADAM17-dependent epidermal growth factor receptor activation and zonula occludens-1 rearrangement. J Pharmacol Exp Ther 334:775-83
Baldys, Aleksander; Gooz, Monika; Morinelli, Thomas A et al. (2009) Essential role of c-Cbl in amphiregulin-induced recycling and signaling of the endogenous epidermal growth factor receptor. Biochemistry 48:1462-73
Kramarenko, Inga I; Bunni, Marlene A; Morinelli, Thomas A et al. (2009) Identification of functional bradykinin B(2) receptors endogenously expressed in HEK293 cells. Biochem Pharmacol 77:269-76
Turner, Justin H; Garnovskaya, Maria N; Coaxum, Sonya D et al. (2007) Ca2+-calmodulin and janus kinase 2 are required for activation of sodium-proton exchange by the Gi-coupled 5-hydroxytryptamine 1a receptor. J Pharmacol Exp Ther 320:314-22
Turner, Justin H; Garnovskaya, Maria N; Raymond, John R (2007) Serotonin 5-HT1A receptor stimulates c-Jun N-terminal kinase and induces apoptosis in Chinese hamster ovary fibroblasts. Biochim Biophys Acta 1773:391-9
Mukhin, Yurii V; Gooz, Monika; Raymond, John R et al. (2006) Collagenase-2 and -3 mediate epidermal growth factor receptor transactivation by bradykinin B2 receptor in kidney cells. J Pharmacol Exp Ther 318:1033-43
Turner, Justin H; Raymond, John R (2005) Interaction of calmodulin with the serotonin 5-hydroxytryptamine2A receptor. A putative regulator of G protein coupling and receptor phosphorylation by protein kinase C. J Biol Chem 280:30741-50
Turner, Justin H; Gelasco, Andrew K; Raymond, John R (2004) Calmodulin interacts with the third intracellular loop of the serotonin 5-hydroxytryptamine1A receptor at two distinct sites: putative role in receptor phosphorylation by protein kinase C. J Biol Chem 279:17027-37
Mukhin, Yurii V; Garnovskaya, Maria N; Ullian, Michael E et al. (2004) ERK is regulated by sodium-proton exchanger in rat aortic vascular smooth muscle cells. J Biol Chem 279:1845-52

Showing the most recent 10 out of 29 publications