Renal Mechanisms Section

Mark A Knepper, MD, PhD, Principal Investigator

	Fluorescence image of 2-dimensional gel showing response of proteome of rat inner medullary collecting duct to long-term vasopressin treatment. Read more.

The chief objective of the Renal Mechanisms section is to discover the fundamental mechanisms involved in regulation of the transport of water, urea and ions by the kidney, and to discover how these regulatory processes are altered in various clinically important fluid and electrolyte disorders. A 'systems biology' approach is utilized. A wide variety of technical approaches are used including 1) in vitro perfusion of microdissected renal tubule segments to measure ion and water fluxes; 2) immunochemical approaches to assess the abundance, intracellular distribution, and post-translational modification of physiologically important transporters; 3) biochemical analysis of microdissected renal tubule segments; 4) knockout mouse models; and 5) mass-spectrometry based proteomics methods; 5) mathematical modeling of the kidney as a complex system.

A major current emphasis is on regulatory systems involved in controlling water excretion by the kidney including mechanisms of aquaporin-2 regulation and the role of urea transporters in the urinary concentrating mechanism. Studies are also being conducted on the molecular basis of disordered renal NaCl transport in hypertension and congestive heart failure.

LKEM Proteomics Databases

Relevant recent publications include:

1. Fenton RA, Chou CL, Stewart GS, Smith CP, Knepper MA. Urinary concentrating defect in mice with selective deletion of phloretin-sensitive urea transporters in the renal collecting duct. Proc Natl Acad Sci U S A. 2004; 101:7469-74.

2. Pisitkun T, Shen RF, Knepper MA. Identification and proteomic profiling of exosomes in human urine. Proc Natl Acad Sci U S A. 2004; 101:13368-13373.

4. Chou CL, Christensen BM, Frische S, Vorum H, Desai RA, Hoffert JD, De Lanerolle P, Nielsen S, Knepper MA. Nonmuscle myosin II and myosin light chain kinase are downstream targets for vasopressin signaling in the renal collecting duct. J Biol Chem. 2004 19; 279: 49026-49035.

4. Hoffert JD, Chou CL, Fenton RA, Knepper MA. Calmodulin is required for vasopressin-stimulated increase in cyclic AMP production in inner medullary collecting duct. J Biol Chem. 2005; 280:13624-13630.

5. Barile M, Pisitkun T, Yu MJ, Chou CL, Verbalis MJ, Shen RF, Knepper MA. Large-scale protein identification in intracellular aquaporin-2 vesicles from renal inner medullary collecting duct. Mol Cell Proteomics. 2005; 4: 1095-1106.

6. Pisitkun T, Bieniek J, Tchapyjnikov D, Wang G, Wu WW, Shen RF, Knepper MA. High-throughput identification of IMCD proteins using LC-MS/MS. Physiol Genomics. 2006; 25:263-76.

7. Hoffert JD, Pisitkun T, Wang G, Shen RF, Knepper MA. Quantitative phosphoproteomics of vasopressin-sensitive renal cells: Regulation of aquaporin-2 phosphorylation at two sites. Proc Natl Acad Sci U S A. 2006; 103:7159-64.

Publications

Questions, comments and suggestions about this page may be addressed to Mark Knepper