Chi, Young-In , PhD
Structural and functional studies of HNF1alpha and HNF4alpha
General Research Subject: Both Type 1 And Type 2 Diabetes
Focus: Islet Biology\Beta Cell Growth and Differentiation
Type of Grant: Career Development
Project Start Date: July 1, 2008
Project End Date: June 30, 2013
The pancreatic beta-cells play a major role in insulin production, glucose sensing and insulin secretion, thus people with either a low level of fully-developed beta-cells or defective mature beta-cells would need beta-cell replacement or elevated beta-cell function to maintain normal glucose homeostasis.
There is a network of transcription factors controlling proper development and normal function of beta-cells through their ability to turn on or off specific genes during the critical times. Among these transcription factors, HNF1alpha (Hepatocyte Nuclear Factor 1alpha) and HNF4alpha are the key regulators and the mutations on these protein cause an inherited dominant form of diabetes known as MODY. Therefore, a better understanding of molecular function of these proteins could provide new and better ways to promote maturation, prolong survival and boost insulin secretion in improperly-developed, transplanted and/or engineered islet cells. We have been studying how these proteins function and how MODY mutations disrupt its functions at the molecular level using a method called x-ray crystallography.
This technique allows us to visualize the action of any protein in three dimensions at high resolution, which could provide the framework for drug design to modulate their functions. Well-known examples of structure-based drug design are protease inhibitors of HIV and Gleevac for the treatment for chronic myeloid leukemia. Since HNF1alpha and HNF4alpha exert their function through various macromolecular interactions, we proposed to elucidate the molecular structures of functional higher-order complexes made by HNF1alpha and HNF4alpha. These structures should enhance our understanding of transcription control involved in beta-cell development and function, and rational drug targeting of HNF1alpha and HNF4alpha in order to modulate their activities for enhancement of beta-cell growth and preservation of beta-cell function, and to reverse the adverse effects of the mutations, thus potential treatment for diabetes.
What area of diabetes research does your project cover? What role will this particular project play in preventing, treating and/or curing diabetes?
The proposed project will be directed to understanding beta cell physiology. The proper development and function of insulin-producing beta cells in the pancreas are regulated by the network of transcription factors including HNF1alpha and HNF4alpha, and the mutations in the genes encoding these transcription factors cause dominantly inherited monogenic forms of diabetes known as MODY (mutations in HNF1alpha and HNF4alpha are the most common monogenic causes of diabetes). Thus, our long-term research goal is to understand the molecular mechanism of gene regulation by these beta cell master regulators, and the molecular basis of diabetes-causing mutations found in them. Because these gene-specific transcription factors initiate transcription by recognizing a specific DNA sequence of the target genes and by forming multi-protein transcription initiation complexes, deciphering the molecular details of how the proteins and protein-DNA interact is vital to understand the mechanism of gene regulation and any defects caused by diabetes causing mutations.
We will be employing X-ray crystallography to elucidate the atomic details of molecular interactions involved in functional higher-order complex formation made by HNF1alpha and HNF4alpha in beta cells, which will provide invaluable insight into the underlying molecular mechanism of these master regulators leading to normal insulin production/secretion, and provide the ground work for rational drug targeting of HNF1alpha and HNF4alpha in order to modulate their activities for enhancement of beta-cell growth and preservation of beta-cell function, and to reverse the adverse effects of the mutations, thus potential treatment for diabetes.
If a person with diabetes were to ask you how your project will help them in the future, how would you respond?
We mainly use X-ray crystallography as a tool to elucidate the detailed, three-dimensional structures of target proteins to better understand the molecular function of these proteins. Seeing is believing. This cliché could not be more apt to our field of study. Atomic details of islet factors and their molecular interactions that control the development and normal function of beta cells could provide new and better ways to promote maturation, prolong survival and boost insulin secretion in improperly-developed, transplanted and/or engineered islet cells to various types of diabetes. In the long run, this work will form the basis for rational targeting of beta cell master regulators by designing small molecules that can be used to modulate their activities and reverse the adverse effects by the mutations, an important approach for developing new diabetes therapies.
Why is it important for you, personally, to become involved in diabetes research? What role will this award play in your research efforts?
As a structural biologist, I have undergone mainly technology-oriented training and worked on a wide range of biological macromolecules such as soluble proteins, membrane proteins, and nucleic acids (both RNA and DNA). As my expertise and research skills grew, I looked for a biological system to which I could apply these techniques and I became very interested in diabetes due to its epidemic trend and likelihood of finding druggable targets. Key proteins in various pathways affecting glucose homeostasis can be identified and specifically targeted.
To be better trained in this area, I joined Dr. Steven Shoelson's laboratory at the Joslin Diabetes Center and worked on MODY gene products and other metabolic disorder-associated proteins such as APS, nuclear lamin, and frataxin. During those years, I was also exposed to various disciplines of diabetes research and I feel quite fortunate working at the Joslin Diabetes Center and the Harvard Medical School community as I was routinely in contact with outstanding diabetes investigators, guest speakers, and clinical doctors. Diabetes will remain as the main focus of my research and this award will immensely help our research and likely bring additional external funding for my continuing research.
In what direction do you see the future of diabetes research going?
Islet cell transplantation and regeneration: Type 1 and type 2 diabetes result from the anatomical or functional loss of insulin-producing beta cells of the pancreas. Replacement of these cells through transplantation or regeneration/restoration of stem cells or existing beta cells could offer lifelong treatment for diabetes. However, a major obstacle in implementing treatment is the lack of sufficient islet cell tissue for transplantation. The generation of an alternative source of pancreatic islet cells could provide a limitless source of islet cells for transplantation therapies.
To this end, understanding the basic mechanisms underlying beta cell regeneration and proper function will be essential for producing new cellular therapies for diabetes, which will help to generate large numbers of functional pancreatic islets or beta cells from embryonic or tissue-specific stem/progenitor cells and to restore beta cell function that has become defective in diabetes disease state.
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