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Nicholas Constantine Zachos, Ph.D.

Headshot of Nicholas Constantine Zachos
  • Director, Mouse Physiology Core, Hopkins Conte Digestive Disease
  • Associate Professor of Medicine


Dr. Nicholas Zachos is an Assistant Professor of Medicine in the Gastroenterology and Hepatology division. He studies protein trafficking, advanced imaging, and bioinformatics.

Dr. Zachos holds a PhD from Eastern Virginia Medical School, and completed a postdoctoral fellowship in the division of gastroenterology and hepatology at the Johns Hopkins University School of Medicine before joining the Johns Hopkins faculty. more


  • Director, Mouse Physiology Core, Hopkins Conte Digestive Disease
  • Associate Professor of Medicine

Departments / Divisions

Centers & Institutes



  • Ph.D.; Eastern Virginia Medical School of The Medical College of Hampton Roads - Norfolk (Virginia) (2002)

Additional Training

  • Johns Hopkins University School of Medicine, Division of Gastroenterology and Hepatology, Baltimore, MD, Postdoctoral Fellow

Research & Publications

Research Summary

Dr. Zachos is interested in understanding variations in protein trafficking that occur during pathophysiological conditions that are responsible for the changes in ion and water transport that result in diarrhea. His lab has recently identified a clathrin-independent endocytic pathway as the mechanism responsible for elevated intracellular calcium-mediated inhibition of NHE3 activity in intestinal epithelial cells. His research work utilizes advanced imaging techniques, including confocal and multi-photon microscopy, to characterize protein trafficking of intestinal transporters as well as performing functional assays using fluorescent probes (ratiometric and non-ratiometric) to measure ion transport in cell culture models, intact intestinal tissues and human small intestinal enteroids.

Recent progress in the identification and isolation of human adult intestinal stem cells has led to re-creation of the human intestinal epithelium, including the entire villus-crypt axis, in a 3D culture. Enteroids are comprised of all four types of intestinal epithelial cells, including enterocytes, Paneth, goblet and enteroendocrine cells and recapitulate two major functions of the small intestine: Na+ absorption and Cl- secretion. The laboratory has employed this novel model of the human intestinal epithelium to characterize the effect of rotavirus infection on NHE3-mediated intestinal Na+ absorption.

His research combines bioinformatics and molecular biology to generate cell-penetrating peptides which affect dynamic protein-protein interactions that are necessary for regulation of ion transport activity in intestinal epithelial cells.  Dr. Zachos’ lab has recently demonstrated that this technology can be used to prevent intracellular calcium-mediated inhibition of NHE3 activity and potentially serve as a therapeutic tool in diarrheal diseases in which elevated intracellular calcium occurs.  The work using this technology was recently recognized by the Department of Medicine and was awarded The W. Leigh Thompson Excellence in Research Award in 2012.

Selected Publications

  1. Zachos NC, Alamelumangpuram B, Lee LJ, Kovbasnjuk O. Carbachol-Mediated Endocytosis of NHE3 Involves a Clathrin-Independent Mechanism Requiring Lipid Rafts and Cdc42.  Cellular Physiology and Biochemistry 2013; In Press. 
  2. Zachos NC, Lee LJ, Kovbasnjuk O, Li X, Donowitz M.  PLC- directly binds activated c-Src which is necessary for carbachol-mediated inhibition of NHE3 activity in Caco-2/BBe cells.  American Journal of Physiology Cell Physiology 2013; In Press.
  3. Hartley JL, Zachos NC, Dawood B, Donowitz M, Forman J, Pollitt RJ, Morgan NV, Tee L, Gissen P, Kahr WH, Knisely AS, Watson S, Chitayat D, Booth IW, Protheroe S, Murphy S, Vries ED, Kelly DA, Maher ER.  Mutations in TTC37 Cause Trichohepatoenteric Syndrome (Phenotypic Diarrhea of Infancy).  Gastroenterology 2010; 138:  2388-2398.  PMID: 20176027
  4. Zachos NC, Li X, Kovbasnjuk O, Hogema B, Sarker R, Li M, de Jonge H, Donowitz M.  NHERF3 (PDZK1) contributes to basal and calcium inhibition of NHE3 activity in Caco-2BBe cells.  Journal of Biological Chemistry 2009; 284: 23708-23718.  PMID: 19535329
  5. Zachos NC, van Rossum DB, Li X, Caraveo G, Sarker R, Cha B, Mohan S, Desiderio S, Patterson RL, Donowitz M.  Phospholipase C- binds directly to the Na+/H+ exchanger 3 and is required for calcium regulation of exchange activity.  Journal of Biological Chemistry 2009; 284: 19437-19444.  PMID: 19473983
  6. Zachos NC, Kovbasnjuk O, Donowitz M.  Regulation of intestinal electroneutral sodium absorption and the brush border Na+/H+ exchanger (NHE3) by intracellular calcium.  Annals of the New York Academy of Sciences 2009; 1165: 240-248.  PMID: 19538312
  7. Alex P, Zachos NC, Gonzales L, Centola M, Li X.  Distinct cytokine patterns identified from multiplex profiles of murine DSS and TNBS-induced colitis.  Inflammatory Bowel Disease 2009; 15: 341-352.
  8. Sullivan S, Alex P, Dassapoulos T, Zachos NC, Donowitz M, Brant S, Cuffari C, Conklin L, Podolsky D, Chen Y, Li X.  Downregulation of sodium transporters and NHERF proteins in IBD patients and mouse colitis models: potential contributors to IBD-associated diarrhea.  Inflammatory Bowel Disease 2009; 15: 261-274.  PMID: 18942765
  9. Zachos NC, Hodson C, Kovbasnjuk O, Li X, Thelin WR, Cha B, Milgram S, Donowitz M.  Elevated intracellular calcium stimulates NHE3 activity by an IKEPP (NHERF4) dependent mechanism.  Cellular Physiology and Biochemistry 2008; 22: 693-704.  PMID: 19088451
  10. Zachos NC, Tse M, Donowitz M.  Molecular physiology of intestinal Na+/H+ exchange (NHE).  Annual Reviews of Physiology 2005; 67:411-43.  PMID: 15709964


Contact for Research Inquiries

Phone: 410-614-0128

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