Molecular tools for metalloprotease sub-proteome generation.

Molecular systems biology, the highly challenging post-genomic research area has many different facets like transcriptomics, proteomics, metabolomics, interactomics, modelling of cell cycles, etc. Among them, functional proteomics and interactomics represent exciting fields of research with high relevance towards biochemistry, medicinal chemistry, therapy, biotechnology and bioinformatics. The number of different proteins expressed by a cell under a set of certain conditions and the high dynamic range of these proteins together with different activation states require methods for sub-proteome generation on a mechanistic basis to reduce the amount of data. This can be achieved by application of tailor-made molecular tools that are based on inhibitors or, more generally, on protein ligands. Immobilised protein ligands proved to be suitable for the generation of sub-proteomes by affinity chromatography or by fishing using magnetic beads. Metalloproteases share a catalytically active metal ion in the active site. They can for example be addressed by hydroxamate type inhibitors like marimastat which are suitable for targeting active metalloproteases on a mechanistic basis aiming at the generation of an activity- and affinity-based sub-proteome. For such purposes, modified hydroxamate type inhibitors can be attached to a solid surface, e.g., chromatography material, magnetic beads, or a surface plasmon resonance sensor chip. The latter technique is a valuable tool for the optimisation of binding and elution conditions of biomolecules in affinity chromatography or on experiments using magnetic beads. Preliminary results are reported on the application of these probes in fishing experiments using magnetic beads.

HDAC inhibitors correct frataxin deficiency in a Friedreich ataxia mouse model.

BACKGROUND: Friedreich ataxia, an autosomal recessive neurodegenerative and cardiac disease, is caused by abnormally low levels of frataxin, an essential mitochondrial protein. All Friedreich ataxia patients carry a GAATTC repeat expansion in the first intron of the frataxin gene, either in the homozygous state or in compound heterozygosity with other loss-of-function mutations. The GAA expansion inhibits frataxin expression through a heterochromatin-mediated repression mechanism. Histone modifications that are characteristic of silenced genes in heterochromatic regions occur at expanded alleles in cells from Friedreich ataxia patients, including increased trimethylation of histone H3 at lysine 9 and hypoacetylation of histones H3 and H4. METHODOLOGY/PRINCIPAL FINDINGS: By chromatin immunoprecipitation, we detected the same heterochromatin marks in homozygous mice carrying a (GAA)(230) repeat in the first intron of the mouse frataxin gene (KIKI mice). These animals have decreased frataxin levels and, by microarray analysis, show significant gene expression changes in several tissues. We treated KIKI mice with a novel histone deacetylase inhibitor, compound 106, which substantially increases frataxin mRNA levels in cells from Friedreich ataxia individuals. Treatment increased histone H3 and H4 acetylation in chromatin near the GAA repeat and restored wild-type frataxin levels in the nervous system and heart, as determined by quantitative RT-PCR and semiquantitative western blot analysis. No toxicity was observed. Furthermore, most of the differentially expressed genes in KIKI mice reverted towards wild-type levels. CONCLUSIONS/SIGNIFICANCE: Lack of acute toxicity, normalization of frataxin levels and of the transcription profile changes resulting from frataxin deficiency provide strong support to a possible efficacy of this or related compounds in reverting the pathological process in Friedreich ataxia, a so far incurable neurodegenerative disease.

Histone deacetylase inhibitors reverse gene silencing in Friedreich's ataxia.

Expansion of GAA x TTC triplets within an intron in FXN (the gene encoding frataxin) leads to transcription silencing, forming the molecular basis for the neurodegenerative disease Friedreich's ataxia. Gene silencing at expanded FXN alleles is accompanied by hypoacetylation of histones H3 and H4 and trimethylation of histone H3 at Lys9, observations that are consistent with a heterochromatin-mediated repression mechanism. We describe the synthesis and characterization of a class of histone deacetylase (HDAC) inhibitors that reverse FXN silencing in primary lymphocytes from individuals with Friedreich's ataxia. We show that these molecules directly affect the histones associated with FXN, increasing acetylation at particular lysine residues on histones H3 and H4 (H3K14, H4K5 and H4K12). This class of HDAC inhibitors may yield therapeutics for Friedreich's ataxia.

Synthesis of marimastat and a marimastat conjugate for affinity chromatography and surface plasmon resonance studies.

Immobilized small-molecule inhibitors are suited for enrichment of biomolecules by affinity chromatography, as it is shown for metalloproteinases and an immobilizable derivative of the hydroxamate-type inhibitor marimastat. A new asymmetric synthesis of marimastat is presented that allows for site-specific attachment to a solid surface, e.g., a chromatography matrix or a surface plasmon resonance sensor chip. The latter technique is shown to be a valuable tool for the optimization of binding and elution conditons of biomolecules in affinity chromatography.