This research project encompasses the total synthesis of the remarkably potent guanidinium poison, zetekitoxin AB (ZTX). ZTX has an exceptional ability to block volatage-gated sodium channels (NaV) with picomolar activity. However, the structural features responsible for its increased activity compared to related guanidinium poisons remains unknown. Synthetic efforts toward ZTX will be based on previously synthesized intermediates accessed in the sponsoring lab's synthesis of the related guanidinium toxin, gonyautoxin (GTX). The route is highlighted by a rhodium-catalyzed oxidative cyclization to access ZTX's bis-guanidinium core. Synthetic methodology will be explored and developed accordingly to access ZTX's macroclactam and N-hydroxycarbamate functionalities. A flexible synthesis of ZTX would allow a focused examination of ZTX analogues that could provide insight into specific interactions with sodium channels. Electrophysiology assays will be performed using whole-cell voltage-clamp techniques against all sodium channel isoforms (NaV1.1-9 and NaX), as ZTX has only been tested against three isoforms to date. This will provide an information rich approach to reveal specificity towards any individual channel isoform. A specific isoform inhibitor with picomolar activity would be an extremely valuable tool to study the distribution of specific channel isoforms in injured neurons. Protein mutagenesis will also be used to probe proposed interactions with specific amino acid residues hypothesized to be crucial for small molecule binding. This project's overall goal is to complete the total synthesis of ZTX and increase understanding of NaV channels with respect to ZTX's binding efficacy. The knowledge accrued from this study could lead to new simplified small molecules that hold promise for treating inflammation and neuropathic pain.

Public Health Relevance

The goal of this research project is to develop and execute a total synthesis of zetekitoxin AB (ZTX), an extremely poisonous molecule that causes paralysis by blocking sodium ion channels. Its mode of action makes ZTX an invaluable tool for understanding ion channel protein function, which is directly associated with pain and nerve damage.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
1F32GM112318-01A1
Application #
8907202
Study Section
Special Emphasis Panel (ZRG1-F04A-W (20))
Program Officer
Barski, Oleg
Project Start
2015-03-12
Project End
2017-03-11
Budget Start
2015-03-12
Budget End
2016-03-11
Support Year
1
Fiscal Year
2015
Total Cost
$50,690
Indirect Cost
Name
Stanford University
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
009214214
City
Stanford
State
CA
Country
United States
Zip Code
94304