Pyrimethamine as a potential pharmacological chaperone for late-onset forms of GM2 gangliosidosis.

Abstract

Late-onset GM2 gangliosidosis is composed of two related, autosomal recessive, neurodegenerative diseases, both resulting from deficiency of lysosomal, heterodimeric beta-hexosaminidase A (Hex A, alphabeta). Pharmacological chaperones (PC) are small molecules that can stabilize the conformation of a mutant protein, allowing it to pass the quality control system of the endoplasmic reticulum. To date all successful PCs have also been competitive inhibitors. Screening for Hex A inhibitors in a library of 1040 Food Drug Administration-approved compounds identified pyrimethamine (PYR (2,4-diamino 5-(4-chlorophenyl)-6-ethylpyrimidine)) as the most potent inhibitor. Cell lines from 10 late-onset Tay-Sachs (11 alpha-mutations, 2 novel) and 7 Sandhoff (9 beta-mutations, 4 novel) disease patients, were cultured with PYR at concentrations corresponding to therapeutic doses. Cells carrying the most common late-onset mutation, alphaG269S, showed significant increases in residual Hex A activity, as did all 7 of the beta-mutants tested. Cells responding to PC treatment included those carrying mutants resulting in reduced Hex heat stability and partial splice junction mutations of the inherently less stable alpha-subunit. PYR, which binds to the active site in domain II, was able to function as PC even to domain I beta-mutants. We concluded that PYR functions as a mutation-specific PC, variably enhancing residual lysosomal Hex A levels in late-onset GM2 gangliosidosis patient cells.

• Authors: Gustavo H B Maegawa, Michael Tropak, Justin Buttner, Tracy Stockley, Fernando Kok, Joe T R Clarke, Don J Mahuran
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 282 Issue 12 Pg. 9150-61 (Mar 23 2007) ISSN: 0021-9258 [Print] United States
• PMID: 17237499 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Enzyme Inhibitors
• Folic Acid Antagonists
• Molecular Chaperones
• Hexosaminidase A
• beta-N-Acetylhexosaminidases
• Pyrimethamine

Topics

• Dimerization
• Dose-Response Relationship, Drug
• Enzyme Inhibitors (pharmacology)
• Fibroblasts (metabolism)
• Folic Acid Antagonists (pharmacology)
• Gangliosidoses, GM2 (drug therapy, metabolism)
• Hexosaminidase A
• Humans
• Lysosomes (metabolism)
• Models, Molecular
• Molecular Chaperones
• Mutation
• Mutation, Missense
• Protein Folding
• Pyrimethamine (pharmacology)
• beta-N-Acetylhexosaminidases (antagonists & inhibitors)