Dr. Mark Donowitz, MD, Professor of Medicine and Professor of Physiology, is Director of the Hopkins Center for Epithelial Disorders at The Johns Hopkins University School of Medicine and Founding Director of the NIH/NIDDK Hopkins Conte Digestive Diseases Center for Basic and Translational Research (ended 5/2023).  I am a scientist, GI clinician and administrator.  My scientific focus has been regulation of intestinal Na+ absorption in normal digestive physiology and abnormalities that contribute to diarrheal diseases and use of that information to develop drug therapy for diarrheal diseases. My research group was the first to recognize the mammalian Na+/H+ exchanger (NHE) gene family, to clone the epithelial isoforms, NHE3 and NHE2, and to trace the evolutionary development of this gene family. I have examined structure/function aspects of the exchangers and identified the large, multiprotein complexes through which NHE3 is regulated.  In addition, my group identified a gene family of PDZ containing brush border proteins called the NHERF family, which are scaffolding proteins that interact with NHE3 and are involved in forming the multiprotein complexes, are critical for its regulation, and take part in its association with the cytoskeleton. Our group cloned NHERF2, which is involved in multiple aspects of NHE3 regulation.  I have pioneered use of human mini-intestines (organoids) made from normal human subjects and grown as monolayers to advance understanding of human digestive physiology and pathophysiology especially related to host-pathogen interactions. Our group has developed co-culture approaches by which intestinal inflammatory and immune cells are co-cultured with intestinal enteroids to make the more more closely mimic normal intestine. My clinical interests are in diagnosis and management of chronic diarrheal diseases, including short gut syndrome, inflammatory bowel diseases and celiac disease. . I am a Past President of the American Gastroenterological Association (AGA) and served as President of the AGA Gastroenterology-Research Group. I have received the Distinguished Achievement Award and as well as the Davenport Memorial Prize from the American Physiology Society, the Career Achievement Award in Basic Science in Gastroenterology from the American Gastroenterological Association,  am a Fellow of the American Association for the Advancement of Science, and a member of the American Society of Clinical Investigator and the Association of American Physicians.

Scientific Contributions

• Demonstrated that multiple intestinal neurohumoral substance altered intestinal transport by elevating intracellular Ca2+
• Cloned the epithelial Na/H exchangers NHE2 and NHE3 and demonstrated existence of mammal Na/H exchange family
• Structure-function studies of NHE3
• Demonstrated regulation of NHE3 occurs via large multi-protein signaling complexes formed on the C-terminus
• Cloned second member of NHERF family (NHERF2), recognized existence and named NHERF family
• First laboratory to use human enteroids to study ion transport in human intestine
• Extensive use of human enteroid monolayers to understand diarrheal diseases/host pathogen interactions

 Administrative Roles

• Chief, GI Division, The Johns Hopkins University School of Medicine

• Founding Director of three NIH GI Core Centers
• President GRG
• President Interurban Clinical Club
• President American Gastroenterological Association
• NIH NIDDK/DDN Council
• NIH Dental Institute/Council

Honors

• APS Davenport Memorial Prize
• APS GI Section Distinguished Achieve Award
• AGA Care Achievement Award in Basic Science in Gastroenteology
• ASCI
• AAP
• Fellow, AAAS

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