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Structure determination of T cell protein-tyrosine phosphatase
Lars Fogh Iversen1, Karin Bach Moller, Anja K Pedersen
1Protein Chemistry and Signal Transduction, Novo Nordisk, DK-2880 Bagsvaerd, Denmark. lfiv@novonordisk.com
Abstract:
Protein-tyrosine phosphatase 1B (PTP1B) has recently received much attention as a potential drug target in type 2 diabetes. This has in particular been spurred by the finding that PTP1B knockout mice show increased insulin sensitivity and resistance to diet-induced obesity. Surprisingly, the highly homologous T cell protein-tyrosine phosphatase (TC-PTP) has received much less attention, and no x-ray structure has been provided. We have previously co-crystallized PTP1B with a number of low molecular weight inhibitors that inhibit TC-PTP with similar efficiency. Unexpectedly, we were not able to co-crystallize TC-PTP with the same set of inhibitors. This seems to be due to a multimerization process where residues 130-132, the DDQ loop, from one molecule is inserted into the active site of the neighboring molecule, resulting in a continuous string of interacting TC-PTP molecules. Importantly, despite the high degree of functional and structural similarity between TC-PTP and PTP1B, we have been able to identify areas close to the active site that might be addressed to develop selective inhibitors of each enzyme.
Insights
T-cell protein-tyrosine phosphatase (TC-PTP) forms multimers, hindering inhibitor binding unlike its homolog PTP1B. Researchers identified distinct active site regions, enabling the development of selective inhibitors for both enzymes.
Area of Science:
- Biochemistry
- Structural Biology
- Drug Discovery
Background:
- Protein-tyrosine phosphatase 1B (PTP1B) is a key drug target for type 2 diabetes, with knockout mice exhibiting enhanced insulin sensitivity.
- T-cell protein-tyrosine phosphatase (TC-PTP), highly homologous to PTP1B, has been less studied, and its structural information, particularly its x-ray structure, is lacking.
Purpose of the Study:
- To investigate the structural basis for differential inhibitor binding between TC-PTP and PTP1B.
- To identify potential strategies for developing selective inhibitors for TC-PTP and PTP1B.
Main Methods:
- Co-crystallization attempts of TC-PTP with known PTP1B inhibitors.
- X-ray crystallography to determine the structure of TC-PTP.
- Structural analysis to compare TC-PTP and PTP1B active sites.
Main Results:
- TC-PTP undergoes multimerization via insertion of its DDQ loop (residues 130-132) into the active site of adjacent molecules, preventing co-crystallization with inhibitors.
- Despite structural similarities, unique regions near the TC-PTP active site were identified.
- PTP1B readily co-crystallized with the same set of inhibitors, indicating distinct structural behaviors.
Conclusions:
- TC-PTP's multimerization mechanism explains its resistance to inhibition by PTP1B-targeting compounds.
- Structural differences near the active sites offer opportunities for developing selective inhibitors for TC-PTP and PTP1B.
- This research paves the way for targeted therapies for diseases involving these phosphatases.