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PGC-1α has been implicated in the pathogenesis of neurodegenerative disorders. Several single-nucleotide polymorphisms (SNPs) located in two separate haplotype blocks of PPARGC1A have shown associations with Huntington's disease (HD) and Parkinson's disease, but causative SNPs have not been identified. One SNP (rs7665116) was located in a highly conserved 233 bp region of intron 2. To determine whether rs7665116 is located in an alternative exon, we performed 5'-RLM-RACE from exon 3 and discovered multiple new transcripts that initiated from a common novel promoter located 587 kb upstream of exon 2, but did not contain the conserved region harboring rs7665116. Using real-time polymerase chain reaction, RNase protection assays and northern blotting, we show that the majority of these transcripts are brain specific and are at least equally or perhaps more abundant than the reference sequence PPARGC1A transcripts in whole brain. Two main transcripts containing independent methionine start codons encode full-length brain-specific PGC-1α proteins that differ only at their N-termini (NTs) from PGC-1α, encoded by the reference sequence. Additional truncated isoforms containing these NTs that are similar to NT-PGC-1α exist. Other transcripts may encode potential dominant negative forms, as they are predicted to lack the second LXXLL motif that serves as an interaction site for several nuclear receptors. Furthermore, we show that the new promoter is active in neuronal cell lines and describe haplotypes encompassing this region that are associated with HD age of onset. The discovery of such a large PPARGC1A genomic locus and multiple isoforms in brain warrants further functional studies and may provide new tissue-specific targets for treating neurodegenerative diseases.

Curcumin (1,7-bis(4-hydroxy-3-methoxyphenyl)-1E,6E-heptadiene-3,5-dione or diferuloyl methane) is a polyphenol derived from the Curcuma longa plant, commonly known as turmeric. This substance has been used extensively in Ayurvedic medicine for centuries for its anti-oxidant, analgesic, anti-inflammatory and antiseptic activity. More recently curcumin has been found to possess anti-cancer properties linked to its pro-apoptotic and anti-proliferative actions. The underlying mechanisms of these diverse effects are complex, not fully elucidated and subject of intense scientific debate. Despite increasing evidence indicating that different cation channels can be a molecular target for curcumin, very little is known about the effect of curcumin on chloride channels. Since, (i) the molecular structure of curcumin indicates that the substance could potentially interact with chloride channels, (ii) chloride channels play a role during the apoptotic process and regulation of the cell volume, and (iii) apoptosis is a well known effect of curcumin, we set out to investigate whether or not curcumin could (i) exert a modulatory effect (direct or indirect) on the swelling activated chloride current ICl(swell) in a human cell system, therefore (ii) affect cell volume regulation and (iii) ultimately modulate cell survival. The ICl(swell) channels, which are essential for regulating the cell volume after swelling, are also known to be activated under isotonic conditions as an early event in the apoptotic process. Here we show that long-term exposure of a human kidney cell line to extracellular 0.1-10 μM curcumin modulates ICl(swell) in a dose-dependent manner (0.1 μM curcumin is ineffective, 0.5-5.0 μM curcumin increase, while 10 μM curcumin decrease the current), and short-term exposure to micromolar concentrations of curcumin does not affect ICl(swell) neither if applied from the extracellular nor from the intracellular side - therefore, a direct effect of curcumin on ICl(swell) can be ruled out. Furthermore, we show that curcumin exposure induces apoptosis in human kidney cells, and at a concentration of 5.0-10 μM induces the appearance of a sub-population of cells with a dramatically increased volume. In these cells the regulation of the cell volume seems to be impaired, most likely as a consequence of the ICl(swell) blockade. Similarly, 50 μM curcumin induced apoptosis, caused cell cycle arrest in G1-phase and increased the volume of human colorectal adenocarcinoma HT-29 cells. The cell cycle arrest in G1 phase may be the mechanism underlying the volume increase observed in this cell line after exposure to curcumin.

Reduction of Cellular Expression Levels Is a Common Feature of Functionally Affected Pendrin (SLC26A4) Protein Variants

IClnis a cloned chloride channel paramount for regulatory volume decrease. Two different loci that carry the coding region for IClnwere identified in the human genome. By PCR strategies an intronless copy of the gene was located on chromosome 6 at position 6p12.1–6q13 (CLNS1B). By fluorescencein situhybridization a copy carrying introns with a putative length of 19 kb was located at chromosome 11 on position 11q13.5–q14.1 (CLNS1A). The characterization and chromosomal localization of the IClngene offer the opportunity to study the regulatory sites of this gene in greater detail and could be helpful in establishing linkages between IClnand potential human diseases.