Chai research group
Pathophysiology of Diabetic Complications
Key terms: Diabetes, Diabetic Complications, Diabetic Nephropathy, Renal Fibrosis, Diabetic Vascular Disease, Cell Division Autoantigen 1 (CDA1), Transforming Growth Factor-beta (TGF-β), target validation, drug development, preclinical study.
To understand pathophysiology of diabetes associated injury in kidney and blood vessels in order to identify and validate new molecular targets for development of novel therapeutic agents to prevent, retard and treat diabetic complications such as diabetic nephropathy and diabetes associated vascular disease.
Feb 2017. L-R Dr Tieqao Wu (postdoc), Dr Zhong-Lin Chai (group leader), Mr Pacific Huynh (PhD student). Absent: Mr Jiaze Li
We initially identified and cloned Cell Division Autoantigen 1 (CDA1). After an extensive study on CDA1 biology, including using cultured cells, laboratory animals and clinical biopsy samples, we have now established a pivotal role for CDA1 in the pathogenesis of diabetic nephropathy (DN), a life threatening kidney disease that occurs in a significant number of diabetic subjects. Our primary finding suggests that CDA1 is a potential drug target to combat DN. As a strategy to pharmacologically target CDA1, we have recently developed a prototype peptide inhibitor, named CHA-061, which can reduce renal injury in a mouse model of DN.
We are now focusing on comprehensively assessing CHA-061 in several DN models relevant to both type 1 and type 2 diabetes. These studies will further validate CDA1 pathway as an efficacious and potentially safe drug target with the new data from these studies serving as a comparison point for evaluating new inhibitors.
We are currently collaborating with experts in multidisciplinary fields from The Monash Institute of Pharmaceutical Sciences (MIPS) and CSIRO to further improve the performance of CHA-061 as well as to convert it to a small molecule inhibitor. Our research approaches include molecular biology, cell biology, protein chemistry, crystallography, structure based design and modification of peptide and small molecule inhibitors as well as preclinical animal studies.
Projects and Opportunities
Honours, Masters and PhD research projects are available in the laboratory. Please contact us to discuss the details of the projects and to see how they fit in your specific interests. Please refer to the following general description of our current projects.
Project 1: Characterization of the prototype inhibitor of CDA1, CHA-061, in diabetic nephropathy in Akita mice
Description: This project seeks to comprehensively characterize our prototype inhibitor of CDA1, CHA-061, for its treatment effect on diabetes associated kidney disease in Akita diabetic mice. The Akita mouse (Ins2Akita) harbours a mutation in the insulin 2 gene (Ins2C96Y), leading to impaired insulin secretion. This mouse model of diabetes with insulin insufficiency is relevant to type 1 (juvenile onset) diabetes as seen in clinical practice. The heterozygous Akita mice are viable and fertile, and develop hyperglycaemia, hypoinsulinemia, polydipsia and polyuria at 3-4 weeks of age. Renal injury in association with diabetes at 4-6 months of age becomes overt with a marked increase in albuminuria, development of renal fibrosis accompanied by a series of histological, molecular and biochemical changes. Akita diabetic and WT non-diabetic control mice will be treated with our CDA1 inhibitor at the age of 8 or 16 weeks for 10 weeks before being killed at the age of 4 and 6 months, respectively, for analysis of relevant renal endpoints. Dedicated animal technicians are available to assist students with animal handling and caring. Senior researchers and fellow students are also available in the lab to guide and assist with performing a broad range of laboratory experiments. This includes analysis of biological samples involving the use of molecular, biochemical and histological techniques to measure expression levels of specific genes implicated in the functional and structural features of diabetic kidney disease as well as assessing relevant signaling molecules. In vitro studies including the use of cultured cells will also be performed to complement the in vivo findings and to further delineate the molecular mechanisms underlying the action of the inhibitor.
Project 2: Characterization of the prototype inhibitor of CDA1, CHA-061, in diabetic nephropathy in db/db mice
Description: This project seeks to comprehensively characterize our prototype inhibitor of CDA1, CHA-061, for its treatment effect on diabetes associated kidney disease in db/db diabetic mice. The db/db mouse has a mutation in leptin receptor, which leads to obesity and onset of diabetes at the age of 3-4 weeks, with typical features of DN such as albuminuria, renal fibrosis and glomerular sclerotic injury seen at 16-18 weeks of age. This mouse model of diabetes is relevant to the most common form of diabetes seen in clinical practice, type 2 (maturity onset) diabetes. Diabetic db/db and control db/h mice will be treated with the prototype inhibitor, CHA-061, at the age of 8 or 16 weeks for 10 weeks. Relevant renal endpoints of these mice will be analyzed. Dedicated animal technicians are available to assist students with animal handling and caring. Senior researchers and fellow students are also available in the lab to guide and assist with performing a broad range of laboratory experiments. This includes analysis of biological samples involving the use of molecular, biochemical and histological techniques to measure expression levels of specific genes implicated in the functional and structural features of diabetic kidney disease as well as assessing relevant signaling molecules. In vitro studies including the use of cultured cells will also be performed to complement the in vivo findings and to further delineate the molecular mechanisms underlying the action of the inhibitor.
Project 3: To improve the potency of CHA-061, the prototype peptide inhibitor of CDA1
Description: This project seeks to further improve the behavior of our prototype peptide inhibitor CHA-061 against the profibrotic effect of CDA1. CHA-061 is a Retro Inverso D amino acid peptide containing a short sequence of a newly identified CDA1 binding protein and a previously described “Cell Penetrating Peptide” (CPP). The CDA1 binding protein part of the CHA-061 inhibitor competitively binds to CDA1 leading to inhibition of formation of the CDA1 complex with its key binding partner protein in the cells. The CPP part of CHA-061 assists with cellular entry of the inhibitor. The theme of this project is to modify this prototype peptide inhibitor and/or to convert it, based on the structure of the CDA1/CHA-061 binding interface, to a new orally bioavailable small molecule inhibitor. The approaches include screening residue substitution derivative peptides using relevant assays (both cell-free and cell based assays), solving CDA1/CHA-061 binding structures by crystallography, medicinal chemistry modification and screening for low molecular weight chemical fragments which bind to CDA1 (Fragment-based Lead Discovery, or FBLD). This is an ideal project for a researcher interested in pharmacology, structural biology and drug discovery.
Current project funding
- 2017-19 Cooper ME, Chai Z, Peat T, Chalmers D. Alfred Research Trusts Major Grant A16049. Pharmacological inhibition of a novel target to reduce renal fibrosis.
- 2016-17 Chai Z. Bayer Pharma AG, Germany, Focus Grant 2016-03-1558. To Target novel CDA1/CDA1BP1 axis in diabetic nephropathy.
Pubmed link [Chai Z]
- Chai Z, Sarcevic B, Mawson A, Toh BH: SET-related cell division autoantigen-1 (CDA1) arrests cell growth. J Biol Chem 2001;276:33665-33674
- Tu Y, Wu W, Wu T, Cao Z, Wilkins R, Toh BH, Cooper ME, Chai Z: Antiproliferative autoantigen CDA1 transcriptionally up-regulates p21(Waf1/Cip1) by activating p53 and MEK/ERK1/2 MAPK pathways. J Biol Chem 2007;282:11722-11731
- Pham Y, Tu Y, Wu T, Allen TJ, Calkin AC, Watson AM, Li J, Jandeleit-Dahm KA, Toh BH, Cao Z, Cooper ME, Chai Z: Cell division autoantigen 1 plays a profibrotic role by modulating downstream signalling of TGF-beta in a murine diabetic model of atherosclerosis. Diabetologia 2010;53:170-179
- Tu Y, Wu T, Dai A, Pham Y, Chew P, de Haan JB, Wang Y, Toh BH, Zhu H, Cao Z, Cooper ME, Chai Z: Cell division autoantigen 1 enhances signaling and the profibrotic effects of transforming growth factor-beta in diabetic nephropathy. Kidney Int 2011;79:199-209
- Chai Z, Dai A, Tu Y, Li J, Wu T, Wang Y, Hale LJ, Koentgen F, Thomas MC, Cooper ME: Genetic Deletion of Cell Division Autoantigen 1 Retards Diabetes-Associated Renal Injury. J Am Soc Nephrol 2013;24:1782-1792