Our group investigates peptides and structure-activity relationships. As chemical messengers of biological information, peptides present one of the most promising classes of compounds in the preliminary stages of pharmaceutical development. The goal of the peptide biochemist is to determine which portions of the peptide molecule are responsible for interacting with binding sites (receptors) to bring about a biological response. Through structure-activity studies, the selectivity and potency of the peptide drug can be improved, enhancing the desired action while eliminating harmful side effects. The basic approach involves a systematic modification of individual amino acid residues by varying certain chemical properties such as chirality, lipophilicity, electronic character, steric bulk, rotational barriers, and hydrogen bond profiles. This influences the three-dimensional structure of the peptide, including peptide backbone bond angles and side chain conformation, which in turn determines the behavior of the molecule.

Type II diabetes develops due to a combination of insulin resistance and decreased insulin secretion. A key factor in the development of Type II diabetes is the loss of insulin producing beta-cells. Human Islet Amyloid Polypeptide (hIAPP) is believed to play a crucial role in this process since fibers of this peptide are found post-mortem in the islets of Langerhans of pancreatic beta-cells in the vast majority (>90 %) of Type II diabetic patients.

Recent evidence suggests that the mature fibers are not the cytotoxic species of hIAPP. Small, soluble oligomeric species of hIAPP have been implicated in disrupting cellular homeostasis by binding to and disrupting the cellular membrane. However, the exact mechanism of this process is unknown. Our collaborators at The University of Michigan are pursuing studies to determine the mechanism of cytotoxicity of hIAPP. In conjunction with their efforts, we are designing inhibitors that block the pathological action of hIAPP and testing their activity through a combination of biophysical techniques. We characterize the interaction of hIAPP with the synthesized inhibitors in the presence of phospholipid membranes in an effort to inhibit its oligomerization, aggregation and membrane permeabilization.

The novelty in our peptide design lies in the fact that few researchers have looked at the region of insulin with which hIAPP binds in the design of inhibitors. Most reports in the literature focus on the modification of the amyloidogenic fragment of hIAPP itself (residues 20-29 or residues 14-18) and the non-amyloidogenic rat variant. It is known that insulin, which is co-secreted with hIAPP from the beta-cell, acts as an inhibitor of hIAPP’s oligomerization and eventual aggregation. Our peptide analogs are modeled on the fragment of insulin that makes direct contact with hIAPP to block its aggregation, HLVEALYLVC. This decapeptide covers the entire recognition region, but we speculate that the internal pentapeptide ALYLV is most important since this region has sequence homology with the segment of IAPP with which it makes contact. We will first perform a truncation study to find the smallest internal fragment that shows inhibitory properties. Unnatural amino acids will then be incorporated at the Y position to alter conformation and/or increase the surface area for pi stacking interactions that are believed to drive the aggregation process. Other compounds with large hydrophobic and aromatic surfaces have been shown to inhibit the aggregation process, mostly likely via the formation of their own pi stacking interactions with hIAPP.

Several methods will be employed to determine the effect of these inhibitors on membranes, including measurement of dye leakage from vesicles (utilizing fluorescence spectroscopy), cross-linking analysis using glutaraldehyde and standard SDS-PAGE techniques, differential scanning calorimetry (to monitor changes in molar heat capacity due to peptide-induced disorder in the membrane), and THT-fluorescence and Congo Red staining for the presence of amyloid fibers. Our collaborators are using 31P, 13C, 15N and 2H solid-state NMR experiments to give clear indications of the process by which peptide-induced membrane disruption occurs; these experiments can be performed in the presence of our inhibitors to discern any differences in behavior. Determination of the mechanism (interference with pi stacking forces to block oligomer formation, inhibition of membrane interaction, etc.) can lead us in the design of even better inhibitors.

Courses Taught at EMU:

Fundamentals of Chemistry Lab (Chem 118)
Fundamentals of Organic and Biochemistry (Chem 120)
Survey of Organic Chemistry (Chem 270-271)
Foundations of Biochemistry (Chem 351)
Biochemistry I and II (Chem 451-453)
Biochemistry III (Chem 551)
Special Topics in Biochemistry (Chem 591)

Professional Affiliations:

American Chemical Society
American Peptide Society

Selected Publications:

"Variation of the pKa in the N-Terminal Tyrosine Side Chain in Octapeptide Analogs of Tendamistat Influences a-Amylase Inhibition" D.L. Heyl, B. Sethi, A. Rogalski, C.E. Bowen, M. Lawrence, L. Beitler, E. Harning, A. Hancer, S. Sreekumar and S. Fernandes, (2007) Protein and Peptide Letters, 14, 497-501

"Membrane Fragmentation by an Amyloidogenic Fragment of Human Islet Amyloid Polypeptide Detected by Solid-State NMR Spectroscopy of Membrane Nanotubes" Jeffrey R. Brender, Ulrich H.N. Durr, Deborah L. Heyl, Mahender B. Budarapu, Ayyalusamy Ramamoorthy, (2007) Biochem. Biophys. Acta., in press

"Deletion of All Cysteines in Tachyplesin I Abolishes Hemolytic Activity and Retains Antimicrobial Activity and LPS Selective Binding" A. Ramamoorthy, S. Thennarasu, A. Tan, Kiran Gottipati, Sreeja Sreekumar, Deborah L. Heyl, F.Y.P.An and C.E. Shelburne, (2006) Biochemistry, 45, 6529-6540

"Correlation of LUMO Localization with the a-Amylase Inhibition Constant in a Tendamistat-Based Series of Linear and Cyclic Peptides", Deborah L. Heyl, Steve Fernandes, Leena Khullar, Jennifer Stephens, Elizabeth Blaney, Horacia Opang-Owusu, Benjamin Stahelin, Todd Pasko, Jana Jacobs, Danielle Bailey, Dennis Brown and Maria C. Milletti, (2005) Bioorganic & Medicinal Chemistry 13/13, 4262-4268.

"Peptide Inhibitors of a-Amylase Based on Tendamistat: Development of Analogues with w-Amino Acids Linking Critical Binding Segments", Deborah L. Heyl, Shakila Tobwala, Leo Solomon Lucas, A. Dammika Nandanie, Rebecca W. Himm, Jennifer Kappler, Elizabeth J. Blaney Jason Groom, Jeffrey Asbill, Jonathan K. Nzoma, Cara Jarosz, Hanna Palamma, and Stephen E. Schullery (2005) Protein and Peptide Letters, 12, 275-280.

"pKa and volume of residue one influence d/m opioid binding: QSAR analysisof tyrosine replacement in a nonselective deltorphin analog", Deborah L. Heyl, Stephen E. Schullery, Kutralanathan Renganathan, Malika N. Jayamaha, David W. Rodgers, and John R. Traynor (2003) Bioorganic & Medicinal Chemistry, 11/17, 3761-3768.

"The role of backbone conformation in deltorphin II binding: A QSAR study of new analogs modified in the 5, 6 positions of the address domain", Stephen E. Schullery, David W. Rodgers, Sakambari Tripathy, Don Eranda Jayamaha, Medha D. Sanvordekar, Kutralanathan Renganathan, Carol Mousigian, and Deborah L. Heyl (2001) Bioorganic & Medicinal Chemistry 9/10, 2633-2642.

"The role of backbone conformation in deltorphin II binding: A QSAR study of new analogs modified in the 5, 6 positions of the address domain", Stephen E. Schullery, David W. Rodgers, Sakambar Tripathy, Don Eranda Jayamaha, Medha D. Sanvordekar, Kutralanathan Renganathan, carol Mousigian and Deborah L. Heyl (2000) Bioorganic & Medicinal Chemistry 9/10, 2633-2642.

"Synthesis of a New Group of Deltorphin I/II Alalogs Modified in the Address Domain with gamma-Amino Acids, and QSAR Study of their delta/mu Opioid Binding", Debroah L. Heyl, Medha D. Sanvordekar, Guzin Dogruyol, Mohamed D. Salamoun, David W. Rodgers, Kutralanathan Renganathan, Carol Mousigian, Stephen E. Schullery (1999) Protein and Peptide Letters, 6(6), 359-366

"Binding to d and m opioid receptors by deltorphin I/II analogs modified at the Phe3 and Asp4/Glu4 side chains: A report of 32 new analogs and a QSAR study", Stephen E. Schullery, Tasneem Mohammedshah, Hafida Makhlouf, Eleanor L. Marks, Benjamin S. Wilenkin, Sharleen Escobar, Carol Mousigian, and Deborah L. Heyl (1997) Bioorganic and Medicinal Chemistry, 5(12), 2221-2234.

"Structural requirements for binding to the delta opioid receptor: Alkyl replacements at the third residue of deltorphin I", Deborah L. Heyl, Hassiba Bouzit, and Carol Mousigian (1996) Letters in Peptide Science, 2, 277-284.

"Opioid receptor binding requirements for the delta-selective peptide deltorphin I: Phe3 replacement with ring-substituted and heterocyclic amino acids", Deborah L. Heyl, Meena Dandabathula, Kathleen R. Kurtz, and Carol Mousigian (1995) Journal of Medicinal Chemistry, 38, 1242-1246.

"Substitution of aromatic and nonaromatic amino acids for the Phe3 residue in the delta-selective opioid peptide deltorphin I: Effects on binding affinity and selectivity", Deborah L. Heyl, Sharon J. Schmitter, Hassiba Bouzit, Thomas W. Johnson, Angela M. Hepp, Kathleen R. Kurtz, and Carol Mousigian (1994) International Journal of Peptide and Protein Research, 44, 233-238.

Invited Review: "Developments in the structure-activity relationships for the delta-selective opioid peptides of amphibian skin", D.L. Heyl and S.E. Schullery (1997) Current Medicinal Chemistry, 4, 117-150.