Regina M. Murphy

Smith-Bascom Professor

3635 Engineering Hall
1415 Engineering Drive
Madison, WI 53706

Ph: (608) 262-1587
regina@engr.wisc.edu

Primary Affiliation:
Chemical and Biological Engineering

Additional Affiliations:
Biomedical Engineering,


Profile Summary

 

My group uses biophysical and biochemical approaches to better understand protein misfolding and aggregation in neurodegenerative disorders such as Alzheimer’s and Huntington’s disease. “Amyloid” is a generic term describing fibrillar protein aggregates of a cross-beta sheet structure. Observations of amyloid deposits in brain tissue of patients with neurodegeneration date back about 100 years, but it was not till the mid 1980’s that the protein associated with Alzheimer’s deposits, beta-amyloid (Abeta) was sequenced. Since then, a number of neurodegenerative disorders have been linked to amyloid protein deposits. These proteins differ in sequence and native structure, but all misfold into structurally related aggregates. The generally accepted hypothesis is that formation of amyloid is a causative event in disease pathology.

Abeta is a small (4 kDa) proteolytic product of the precursor protein APP. As a monomer, Abeta is natively unfolded, but it spontaneously self-associates into dimers, larger oligomers, and fibrillar aggregates. The deposition of Abeta fibrils as amyloid deposits in the brain is one of the defining pathological features of Alzheimer’s disease (AD). Most researchers believe that Abeta aggregation is the primary cause of the neuronal degeneration observed in this disease. We are currently exploring the hypothesis that a common protein, transthyretin (TTR), serves to regulate Abeta aggregation and suppress its toxicity. We hypothesize that TTR is a natural anti-Alzheimer’s ‘drug’. In our work, done in collaboration with Dr. Jeff Johnson (Pharmacy), we are identifying the specific Abeta-binding site on TTR, delineating the detailed mechanism by which Abeta interacts with TTR, and designing peptidomimetics that mimic the Abeta-sequestering activity of TTR. 

One of the intriguing findings from our work was that the domain on TTR that binds to Abeta is predicted to be ‘amyloidogenic’ itself. Another intriguing finding is that initial binding of Abeta to  causes TTR dissociation – which is considered to be the first step on the pathway of TTR fibril formation. In other words, if homotypic (self) indefinite interaction occurs, either Abeta or TTR will form large toxic aggregates. However, heterotypic interaction between Abeta and TTR, involving the same domains that drive self-association, appears to prevent toxicity. Based on these findings, we hypothesize that there is an amyloid regulatory network. Specifically, heterotypic interactions, driven through amyloidogenic domains, compete with homotypic interactions and inhibit the growth of toxic self-assemblies. We are beginning studies to test this hypothesis over a broad range of amyloid-forming proteins and peptides. 

Huntington’s disease is characterized by the abnormal expansion of a glutamine repeat domain in the protein huntingtin. Expansion leads to aggregation of huntingtin, which is believed to cause neuronal cell death. The fact that expanded glutamine domains would cause aggregation was at first considered surprising, because glutamine is a very hydrophilic residue. This side chain contains both a hydrogen bond donor and hydrogen bond acceptor; as the length of the glutamine repeat increases, multivalent side chain-side chain hydrogen bonding successfully competes with hydrogen bonding to the solvent. We are conducting fundamental studies of the process by which repeat-containing peptides, such as polyglutamine, self-associate. Our studies indicate that fibril growth from peptides containing glutamine repeats occur via hydrophobically driven assembly into disordered (‘liquid-like’) oligomers, which eventually converted to ordered fibrillar aggregates. We are exploring the role of water and dehydration in fibril assembly mechanisms, and examining the aggregation of other repeat-containing peptides such as polyasparagine.

Education

  • S.B., Ph.D., Massachusetts Institute of Technology

Research Interests

  • physical chemistry of protein-protein interactions
  • amyloid protein aggregation

Awards, Honors and Societies

  • Spangler Award for Technology Enhanced Instruction (2013)
  • Elected Fellow, AIMBE (2008)
  • Chancellor\\\'s Teaching Award (2008)
  • James G. Woodburn Award for Excellence in Teaching (2006)
  • Romnes Faculty Fellow (1999)
  • Jordi Folch-Pi Award, American Society for Neurochemistry (1998)
  • S.C. Johnson Distinguished Fellow Award (1997)
  • Alumni Teaching Quality Award (1992)
  • NSF Presidential Young Investigator Award (1990)

Publications

Selected Publications (since 2003)

“Kinetics of Adsorption of Beta-Amyloid Peptide Ab (1-40) to Lipid Bilayers” J. Kremer and R.M. Murphy. Journal of Biochemical and Biophysical Methods, 57:159-169 (2003)

“Targeted Control of Kinetics of Beta-Amyloid Self-Association by Surface Tension-Modifying Peptides”. J.R. Kim, T. J. Gibson, and R. M. Murphy Journal of Biological Chemistry, 278: 40730 – 40735 (2003)

 “Mechanism of Accelerated Assembly of b-Amyloid Filaments into Fibrils by KLVFFK6” J.R. Kim and R. M. Murphy, Biophysical Journal 86:3194-3203 (2004)

 “Urea Modulation of b-Amyloid Fibril Growth: Experimental Studies and Kinetic Modeling”. J.R. Kim, A. Muresan, K.Y.C. Lee and R.M. Murphy. Protein Science, 13:2888-2898 (2004)

 “Design of Peptidyl Compounds that Affect Beta-amyloid Aggregation: Importance of Surface Tension and Context”, T.J. Gibson and R. M. Murphy. Biochemistry, 44:8898-8907 (2005)

“Structural Characterization of Apomyoglogin Self-Associated Species in Aqueous Buffer and Urea Solution. C. Chow, N. Kurt, R. M. Murphy and S. Cavagnero. Biophys. J. 90:298-309 (2006)

 “Predicting Solvent and Aggregation Effects of Peptides using Group Contribution Methods”. J. R. Kim, T. J. Gibson, and R. M. Murphy. Biotechnol. Prog. 22;605-608 (2006)

“Phage Display Affords Peptides that Modulate b-Amyloid Aggregation”. B. P. Orner, L. Liu, R. M. Murphy and L. L. Kiessing. J. Am. Chem. Soc., 128:11882-11889, (2006)

“Kinetics of Inhibition of Beta-Amyloid Aggregation by Transthyretin”. L. Liu and R. M. Murphy. Biochemistry 45:15702-15709, (2006)

“Kinetics of Amyloid Formation and Membrane Interactions with Amyloidogenic Proteins”. R. M. Murphy. Biochim. Biophys. Acta. 1768:1923-1934 (2007)

 “Reconsidering the Mechanism of Polyglutamine Peptide Aggregation”. C. C. Lee, R. H. Walters, and R. M. Murphy. Biochemistry 46: 12810-12820 (2007)

“A Strategy for Generating Polyglutamine ‘Length Libraries’ in Model Host Proteins.” M. D. Tobelmann, R. L. Kerby, and R. M. Murphy. Protein Eng. Des. Sel. 21:161-164 (2008)

“Model Discrimination and Mechanistic Interpretation of Kinetic Data in Protein Aggregation Studies.” J. P. Bernacki and R. M. Murphy. Biophys. J. 96: 2871-2887 (2009) 

“Differential Modification of Cys10 Alters Transthyretin’s Effect on Beta-Amyloid Aggregation and Toxicity”. L. Liu, J. Hou, J. L.Du, R. S. Chumanov, Q. G. Xu, Y. Ge, J. A. Johnson and R. M. Murphy. Prot. Eng. Des. Sel. 22: 479-488 (2009) 

“Examining Polyglutamine Peptide Length: A Connection between Collapsed Conformations and Increased Aggregation”. R. H. Walters and R. M. Murphy J. Mol. Biol. 393: 978-992 (2009). 

 “Characterizing the Interaction of Beta-Amyloid with Transthyretin Monomers and Tetramers”. J. Du and R. M. Murphy. Biochemistry 49: 8276-8289 (2010) 

“Location Trumps Length: Polyglutamine-Mediated Changes in Folding and Aggregation of a Host Protein” M.D. Tobelmann and R. M. Murphy. Biophysical J. 100:2773-2782 (2011)  

 “Aggregation Kinetics of Interrupted Polyglutamine Peptides” R. H. Walters and R. M. Murphy, J. Mol. Biol. 412:505-519 (2011) 

“Length-dependent Aggregation of Uninterrupted Polyalanine Peptides” J. P. Bernacki and R. M. Murphy. Biochemistry 50:9200-9211 (2011) 

“When More is Not Better: Expanded Polyglutamine Domains in Neurodegenerative Disease”. R. M. Murphy, R. H. Walters, M. D. Tobelmann, and J. P. Bernacki. In Non-fibrillar Amyloidogenic Protein Assemblies – Common Cytotoxins Underlying Degenerative Diseases, F. Rahimi and G. Bitan, editors. Springer Books. (2012)

“Elongation Kinetics of Polyglutamine Peptide Fibrils: A Quartz Crystal Microbalance with Dissipation Study”. R. H. Walters, K. H. Jacobson, J. A. Pedersen, and R. M. Murphy. J. Mol. Biol. 412:329-347 (2012) 

“Identification of Beta-Amyloid-Binding Sites on Transthyretin”, J. Du, P. Y. Cho, D. T. Yang, and R. M. Murphy. Prot. Eng. Des. Sel. 25:337-345 (2012) 

“Analysis of Aggregation Kinetic Data”. R. M. Murphy. Meth. Mol. Biol. (in press)

“Insights into the Molecular Mechanism of Protein Native-Like Aggregation Upon Glycation” L. M. Olivera, R. A. Gomes, D. Yang, S. R. Dennison, C. Familia, A. Lages, A. V. Coelho, R. M. Murphy, D. A. Phoenix and A. Quintas. Biochem. Biophys Acta 1834:1010-1022 (2012). 

“Transthyretin as both a Sensor and a Scavenger of b-Amyloid Oligomers” D. T. Yang, G. Joshi, P. Y. Cho, J. A. Johnson, and R. M. Murphy. Biochemistry 52:2849-2861 (2013) 

Courses

Summer 2014

  • BME 699 - Advanced Independent Study

  • BME 399 - Independent Study
  • CBE 489 - Honors in Research
  • CBE 990 - Thesis-Research
  • CBE 890 - Pre-Dissertator\'s Research
  • CBE 790 - Master\'s Research or Thesis
  • CBE 699 - Advanced Independent Studies
  • CBE 599 - Special Problems
  • CBE 450 - Process Design
  • CBE 990 - Thesis-Research
  • CBE 890 - Pre-Dissertator\'s Research
  • CBE 790 - Master\'s Research or Thesis
  • CBE 599 - Special Problems
  • CBE 250 - Process Synthesis
  • Profile Summary

     

    My group uses biophysical and biochemical approaches to better understand protein misfolding and aggregation in neurodegenerative disorders such as Alzheimer’s and Huntington’s disease. “Amyloid” is a generic term describing fibrillar protein aggregates of a cross-beta sheet structure. Observations of amyloid deposits in brain tissue of patients with neurodegeneration date back about 100 years, but it was not till the mid 1980’s that the protein associated with Alzheimer’s deposits, beta-amyloid (Abeta) was sequenced. Since then, a number of neurodegenerative disorders have been linked to amyloid protein deposits. These proteins differ in sequence and native structure, but all misfold into structurally related aggregates. The generally accepted hypothesis is that formation of amyloid is a causative event in disease pathology.

    Abeta is a small (4 kDa) proteolytic product of the precursor protein APP. As a monomer, Abeta is natively unfolded, but it spontaneously self-associates into dimers, larger oligomers, and fibrillar aggregates. The deposition of Abeta fibrils as amyloid deposits in the brain is one of the defining pathological features of Alzheimer’s disease (AD). Most researchers believe that Abeta aggregation is the primary cause of the neuronal degeneration observed in this disease. We are currently exploring the hypothesis that a common protein, transthyretin (TTR), serves to regulate Abeta aggregation and suppress its toxicity. We hypothesize that TTR is a natural anti-Alzheimer’s ‘drug’. In our work, done in collaboration with Dr. Jeff Johnson (Pharmacy), we are identifying the specific Abeta-binding site on TTR, delineating the detailed mechanism by which Abeta interacts with TTR, and designing peptidomimetics that mimic the Abeta-sequestering activity of TTR. 

    One of the intriguing findings from our work was that the domain on TTR that binds to Abeta is predicted to be ‘amyloidogenic’ itself. Another intriguing finding is that initial binding of Abeta to  causes TTR dissociation – which is considered to be the first step on the pathway of TTR fibril formation. In other words, if homotypic (self) indefinite interaction occurs, either Abeta or TTR will form large toxic aggregates. However, heterotypic interaction between Abeta and TTR, involving the same domains that drive self-association, appears to prevent toxicity. Based on these findings, we hypothesize that there is an amyloid regulatory network. Specifically, heterotypic interactions, driven through amyloidogenic domains, compete with homotypic interactions and inhibit the growth of toxic self-assemblies. We are beginning studies to test this hypothesis over a broad range of amyloid-forming proteins and peptides. 

    Huntington’s disease is characterized by the abnormal expansion of a glutamine repeat domain in the protein huntingtin. Expansion leads to aggregation of huntingtin, which is believed to cause neuronal cell death. The fact that expanded glutamine domains would cause aggregation was at first considered surprising, because glutamine is a very hydrophilic residue. This side chain contains both a hydrogen bond donor and hydrogen bond acceptor; as the length of the glutamine repeat increases, multivalent side chain-side chain hydrogen bonding successfully competes with hydrogen bonding to the solvent. We are conducting fundamental studies of the process by which repeat-containing peptides, such as polyglutamine, self-associate. Our studies indicate that fibril growth from peptides containing glutamine repeats occur via hydrophobically driven assembly into disordered (‘liquid-like’) oligomers, which eventually converted to ordered fibrillar aggregates. We are exploring the role of water and dehydration in fibril assembly mechanisms, and examining the aggregation of other repeat-containing peptides such as polyasparagine.


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