Faculty by
Alpha List

Faculty by
Research Area

Students

Administration

 

Faculty

Ari Gafni

Professor of Biological Chemistry
Research Scientist, Biophysics Research Division and Institute of Gerontology

Ph.D., Weizmann Institute
Postdoctoral Fellow, Johns Hopkins University

Research Focus: Protein Misfolding in Aging and Disease

Phone: 734.615.1964
E-mail: arigafni@umich.edu
Fax: 734.764.3323

It is widely recognized that to be biologically functional proteins have to be folded into specific structures and that loss of structure leads to loss of function.  Recent studies have demonstrated that in some cases structural alterations not only lead to loss of function, but can actually convert a protein into a cytotoxic form.  This process features in a number of devastating human diseases including Alzheimer’s disease, Parkinson’s disease, mad cow disease and type-2 diabetes, to mention a few.  In all these diseases a specific protein or peptide is structurally modified and aggregates to form oligomeric species that bind to, and damage, cell membranes leading to cell death.

Current research in our laboratory aims to characterize the molecular origin of this toxicity in the amyloid beta peptide, associated with Alzheimer’s disease, and the islet amyloid peptide associated with type-2 diabetes.  We focus on characterizing the structural alterations and molecular interactions that lead to the development of membrane-bound aggregates of these proteins, and on the mechanism by which these species induce cell death.

Our elucidation of the structural evolution and membrane interactions of these proteins is accomplished using a variety of molecular-biological, biochemical and biophysical approaches. Laser-based optical spectroscopic techniques, and in particular time-resolved fluorescence, Forster resonance energy transfer circular dichroism and light scattering are used to follow protein conformational changes and aggregation in real time and serve in the development and testing of strategies for the inhibition of toxicity. Of special importance to our studies is the application of single molecule microscopy.  This technique allows us to work with very low protein concentrations, as found in vivo, and to obtain unprecedented resolving power by following the interactions of individual peptide oligomers with membranes of live cells.  We are using single molecule microscopy to address mechanistic details of the origin and evolution of cytotoxicity at a level of detail that is impossible to achieve by conventional experimental approaches.

Gafni/Steel Research Group

 

Awards

2002
 Ellison Medical Foundation Senior Scholar Program
2001
 Distinguished Director Award


Representative Publications

  1. Brender, JR, Dertouzos, J, Ballou, DP, Massey, V, Palfey, BA, Entsch, B, Steel, DG and Gafni, A: Conformational dynamics of the isoalloxazine in substrate-free p-hydroxybenzoate hydroxylase: single molecule studies. J. Am. Chem. Soc. 2005; 127 (51), 18171-18178. 

  2. Shi, J, Dertouzos,J, Gafni, A, Steel, DG, Palfey, BA: Single-molecule kinetics reveals signatures of half-sites reactivity in dihydroorotate dehydrogenase A catalysis. Proc. Nat. Acad. Sci. USA 2006; 103 5775-5780. 

  3. Shi, J, Gafni, A and Steel, DG: Simulated Data Sets for Single Molecule Kinetics: Some Limitations and Complications of Data Analysis. Eur. Biophys. J. 2006; 633-645. 

  4. Pattaramanon, N, Sangha, N and Gafni, A: The carboxy-terminal domain of HSF1 is intrinsically unstructured and can be induced to fold. Biochemistry 2007; 46, 3405-3415. 

  5. Brender, JR, Lee, EL, Cavitt, MA, Gafni, A, Steel, DG and Ramamoorthy, A: Amyloid fiber formation and membrane disruption are separate processes localized in two distinct regions of IAPP, the type-2-diabetes related peptide. J. Am. Chem. Soc. 2008, 130, 6424-6429. 

  6. Shi, J., Gafni, A. and Steel, DG: Application of single molecule spectroscopy in studies of enzyme kinetics and mechanisms. Meth. Enzymol. 2008; 450, 129-157. 

  7. Wong, P, Schauerte, JA, Wisser, KC, Ding, H, Lee, E, Steel, DG and Gafni, A: Amyloid-β membrane binding and permeabilization are distinct processes influenced by membrane charge and fluidity. J. Mol. Biol., 2009, 386, 81-96. 

  8. Tapley, T.L., Körner, J.L., Barge, M.T., Hupfeld, J., Schauerte, J.A., Gafni, A., Jakob, U. and Bardwell, J.C.A. A Functional Role for Protein Disorder: Rapid Activation and Substrate Binding in the Miniature Chaperone HdeA. Proc. Natl. Acad. Sci. USA. 2009; 106, 5557-5562. 

  9. Ding, H., Wong, PT, Lee, EL, Gafni, A. and Steel, DG: Determination of the oligomer size of amyloidogenic beta-amyloid(1-40) by single-molecule spectroscopy. Biophys. J. 2009; 97, 912-921. 

  10. Schauerte, JA, Wong, PT, Wisser, KC, Steel, DG and Gafni, A: Distinct Classes of Amyloid Pores Formed by Aβ1-40 on Lipid Bilayers are revealed by Simultaneous Single Molecule Fluorescence and Conductivity Measurements. Biochemistry 2010; 49, 3031-3039. 

  11. Brender JR, Lee EL, Hartman K, Wong PT, Ramamoorthy A, Steel DG, Gafni A: Biphasic effects of insulin on islet amyloid polypeptide membrane disruption. Biophys. J. 100 (2011) 685-692. 

 

 image