Mitochondrial Complex I-III Activity Is Reduced in Cells with Impaired CFTR Function

What is it about?

Cystic fibrosis (CF) is a frequent and lethal autosomal recessive disease. It results from different possible mutations in the CFTR gene, which encodes the CFTR chloride channel. We have previously studied the differential expression of genes in CF and CF corrected cell lines, and found a reduced expression of MTND4 in CF cells. MTND4 is a mitochondrial gene encoding the MTND4 subunit of the mitochondrial Complex I (mCx-I). Since this subunit is essential for the assembly and activity of mCx-I, we have now studied whether the activity of this complex was also affected in CF cells. By using Blue Native-PAGE, the in-gel activity (IGA) of the mCx-I was found reduced in CFDE and IB3-1 cells (CF cell lines) compared with CFDE/6RepCFTR and S9 cells, respectively (CFDE and IB3-1 cells ectopically expressing wild-type CFTR). Moreover, colon carcinoma T84 and Caco-2 cells, which express wt-CFTR, either treated with CFTR inhibitors (glibenclamide, CFTR(inh)-172 or GlyH101) or transfected with a CFTR-specific shRNAi, showed a significant reduction on the IGA of mCx-I.

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Why is it important?

These results confirm the earlier work of Burton Shapiro's laboratory regarding a possible damage to mitochondria in cells derived from cystic fibrosis patients. This "mitochondrial theory" was disregarded for decades after the CFTR was cloned and it was found that constituted a membrana plasma protein with a Cl- channel functions. This and previous results from our lab confirm that Shapiro was right, although the effect over mitochondria are indirect, mediated by CFTR. Some of our previous work related to this one: 1: Clauzure M, Valdivieso AG, Massip Copiz MM, Schulman G, Teiber ML, Santa-Coloma TA. Disruption of interleukin-1β autocrine signaling rescues complex I activity and improves ROS levels in immortalized epithelial cells with impaired cystic fibrosis transmembrane conductance regulator (CFTR) function. PLoS One. 2014 Jun 5;9(6):e99257. doi: 10.1371/journal.pone.0099257. eCollection 2014. PubMed PMID: 24901709; PubMed Central PMCID: PMC4047112. 2: Valdivieso AG, Santa-Coloma TA. CFTR activity and mitochondrial function. Redox Biol. 2013 Feb 5;1:190-202. doi: 10.1016/j.redox.2012.11.007. Review. PubMed PMID: 24024153; PubMed Central PMCID: PMC3757715. 3: Valdivieso ÁG, Clauzure M, Massip-Copiz M, Santa-Coloma TA. The Chloride Anion Acts as a Second Messenger in Mammalian Cells - Modifying the Expression of Specific Genes. Cell Physiol Biochem. 2016;38(1):49-64. doi: 10.1159/000438608. Epub 2016 Jan 8. PubMed PMID: 26741366. 4: Clauzure M, Valdivieso ÁG, Massip-Copiz MM, Mori C, Dugour AV, Figueroa JM, Santa-Coloma TA. Intracellular Chloride Concentration Changes Modulate IL-1β Expression and Secretion in Human Bronchial Epithelial Cultured Cells. J Cell Biochem. 2017 Aug;118(8):2131-2140. doi: 10.1002/jcb.25850. Epub 2017 Apr 18. PubMed PMID: 27996167. 5: Valdivieso AG, Clauzure M, Marín MC, Taminelli GL, Massip Copiz MM, Sánchez F, Schulman G, Teiber ML, Santa-Coloma TA. The mitochondrial complex I activity is reduced in cells with impaired cystic fibrosis transmembrane conductance regulator (CFTR) function. PLoS One. 2012;7(11):e48059. doi: 10.1371/journal.pone.0048059. Epub 2012 Nov 21. PubMed PMID: 23185247; PubMed Central PMCID: PMC3504030. 6: Valdivieso AG, Marcucci F, Taminelli G, Guerrico AG, Alvarez S, Teiber ML, Dankert MA, Santa-Coloma TA. The expression of the mitochondrial gene MT-ND4 is downregulated in cystic fibrosis. Biochem Biophys Res Commun. 2007 May 11;356(3):805-9. Epub 2007 Mar 19. PubMed PMID: 17382898.

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