Letter: White-cell glutathione reductase in cystic fibrosis

CFTR activity and mitochondrial function

Cystic Fibrosis (CF) is a frequent and lethal autosomal recessive disease, caused by mutations in the gene encoding the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). Before the discovery of the CFTR gene, several hypotheses attempted to explain the etiology of this disease, including the possible role of a chloride channel, diverse alterations in mitochondrial functions, the overexpression of the lysosomal enzyme α-glucosidase and a deficiency in the cytosolic enzyme glucose 6-phosphate dehydrogenase. Because of the diverse mitochondrial changes found, some authors proposed that the affected gene should codify for a mitochondrial protein. Later, the CFTR cloning and the demonstration of its chloride channel activity turned the mitochondrial, lysosomal and cytosolic hypotheses obsolete. However, in recent years, using new approaches, several investigators reported similar or new alterations of mitochondrial functions in Cystic Fibrosis, thus rediscovering a possible role of mitochondria in this disease. Here, we review these CFTR-driven mitochondrial defects, including differential gene expression, alterations in oxidative phosphorylation, calcium homeostasis, oxidative stress, apoptosis and innate immune response, which might explain some characteristics of the complex CF phenotype and reveals potential new targets for therapy.

Altered isoenzyme patterns of liver alpha-L-fucosidase in cystic fibrosis

The isoenzyme pattern of alpha-L-fucosidase was studied by isoelectric focusing in livers from seven patients with cystic fibrosis and in normal and pathological (GM1-gangliosidosis, Type II and Sanfilippo disease) controls. The controls had very reproducible patterns consisting of seven isoenzymes of alpha-L-fucosidase with the most neutral from (I) representing a small proportion of the total activity. All seven of the cystic fibrosis livers had altered alpha-L-fucosidase isoenzyme patterns. The chemical relationship of the seven isoenzymes of normal liver alpha-L-fucosidase was investigated using neuramindase. The five most acidic forms of alpha-L-fucosidase appear to be related to the most neutral form by sialic acid residues. Since the isoenzymes of liver alpha-L-fucosidase appear to be related by sialic acid residues, it is possible that the altered alpha-L-fucosidase isoenzyme patterns found in cystic fibrosis livers may result from aberrant sialylation.