Alterations in mitochondrial parameters are an important hallmark of Huntington’s disease (HD). The ubiquitous expression of mutant huntingtin raises the prospect that mitochondrial disturbances can also be detected and monitored through buccal epithelial cells. In a group of 34 patients with Huntington’s disease and a group of 22 age-related healthy volunteers, respiratory complex I and IV protein quantities in buccal epithelial cells were measured using the dipstick immunocapture assay. The protein quantity of respiratory complex I correlates with age (r = 0.427, P = 0.026, FWE-P = 0.156) in the patient group, but not in the group of healthy subjects. Our non-invasive approach allows us to obtain valuable information for the studies of mitochondrial biochemical parameters in patients with neurodegenerative diseases and could also be useful in epidemiological studies. and Corresponding author: Hana Hansíková
Cytochrome c oxidase (COX), the terminal enzyme of the mitochondrial respiratory chain, is one of the key functional and regulatory sites of the mammalian energy metabolism. Owing to the importance of the enzyme, pathogenetic mutations affecting COX frequently result in severe, often fatal metabolic disorders. No satisfactory therapy is currently available so that the treatment remains largely symptomatic and does not improve the course
of the disease. While only few genetic defects of COX are caused by mutations in mitochondrial genome, during the last five years a large number
of pathogenetic mutations in nuclear genes have been discovered. All these mutations are located in genes encoding COX-specific assembly proteins including SURF1, SCO1, SCO2, COX10, and COX15. Despite the identification of increasing number of mutations, their precise etiopathogenetic mechanisms, which are necessary for the development of
future therapeutic protocols, still remain to be elucidated. This review summarizes recent developments, including our efforts in elucidation of the molecular basis of human mitochondrial diseases due to specific defects of COX with special focus on SURF1 assembly protein.
Steroid 5α-reductase type 3 congenital disorder of glycosylation (SRD5A3-CDG) is a severe metabolic disease manifesting as muscle hypotonia, developmental delay, cerebellar ataxia and ocular symptoms; typically, nystagmus and optic disc pallor. Recently, early onset retinal dystrophy has been reported as an additional feature. In this study, we summarize ocular phenotypes and SRD5A3 variants reported to be associated with SRD5A3-CDG. We also describe in detail the ophthalmic findings in a 12-year-old Czech child harbouring a novel homozygous variant, c.436G>A, p.(Glu146Lys) in SRD5A3. The patient was reviewed for congenital nystagmus and bilateral optic neuropathy diagnosed at 13 months of age. Examination by spectral domain optical coherence tomography and fundus autofluorescence imaging showed clear signs of retinal dystrophy not recognized until our investigation. Best corrected visual acuity was decreased to 0.15 and 0.16 in the right and left eye, respectively, with a myopic refractive error of -3.0 dioptre sphere (DS) /-2.5 dioptre cylinder (DC) in the right and -3.0 DS / -3.0 DC in the left eye. The proband also had optic head nerve drusen, which have not been previously observed in this syndrome. and Corresponding author: Petra Lišková
Cox17 is an assembly factor that participates in early cytochrome c oxidase (COX, CcO) assembly stages. Cox17 shuttles copper ions from the cytosol to the mitochondria and, together with Sco1 and Sco2, provides copper ions to the Cox1 and Cox2 mitochondrially encoded subunits. In Saccharomyces cerevisiae, Cox17 also modulates mitochondrial membrane architecture due to the interaction of Cox17 with proteins of the MICOS complex (mitochondrial contact site and cristae organizing system). There is currently no data regarding the impact of long-term Cox17 deficiency in human cells. Here, we present construction and characterization of three stable COX17 shRNA-downregulated HEK293 cell lines that have less than 10 % of the residual Cox17 protein level. Cox17-depleted cell lines exhibited decreased intramitochondrial copper content, decreased CcO subunit levels (Cox1, Cox4 and Cox5a) and accumulation of CcO subcomplexes. Similarly to yeast cells, mitochondria in Cox17-downregulated HEK293 cell lines exhibited ultrastructural changes including cristae reduction and mitochondrial swelling. Characterization of the molecular pathogenesis of long-term Cox17 deficiency complements our knowledge of the mitochondrial copper metabolism and assembly of cytochrome c oxidase in human cells. and Corresponding author: Hana Hansíková
Mitochondrial dysfunction is a potentially important player in the development of insulin resistance and type 2 diabetes mellitus (T2DM). We investigated the changes of mRNA expression of genes encoding main enzymatic complexes of mitochondrial respiratory chain in subcutaneous adipose tissue (SCAT) and peripheral monocytes (PM) of 11 subjects with simple obesity (OB), 16 obese patients with T2DM and 17 healthy lean subjects (C) before and after very low-calorie diet (VLCD) using quantitative real time PCR. At baseline in SCAT, both T2DM and OB group had decreased mRNA expression of all investigated mitochondrial genes with the exception of 2 complex I (NDUFA 12) and complex IV (COX 4/1) enzymes in OB subjects. In contrast, in PM only the expression of complex I enzymes NDUFA 12 and MT-ND5 was reduced in both T2DM and
OB subjects along with decreased expression of citrate synthase (CS) in T2DM group. Additionally, T2DM subjects showed reduced activity of pyruvate dehydrogenase and complex IV in peripheral blood elements. VLCD further decreased mRNA expression of CS and complex I (NT-ND5) and II (SDHA) enzymes in SCAT and complex IV (COX4/1) and ATP synthase in PM of T2DM group, while increasing the activity of complex IV in their peripheral blood elements. We conclude that impaired mitochondrial biogenesis and decreased activity of respiratory chain enzymatic complexes was present in SCAT and PM of obese and diabetic patients. VLCD improved metabolic parameters and ameliorated mitochondrial oxidative function in peripheral blood elements of T2DM subjects but had only minor and inconsistent effect on mitochondrial gene mRNA expression in SCAT and PM.