Spiny keratoderma.

Spiny keratoderma is a rare entity characterized by filiform keratotic lesions on palms and soles. Although there are some inherited cases the majority are acquired. This last variant can be idiopathic or associated with neoplasms and chronic systemic diseases. We report a new case of spiny keratoderma associated with endometrial carcinoma.

C4.4A as a candidate marker in the diagnosis of colorectal cancer.

C4.4A is a member of the Ly-6 family with restricted expression in non-transformed tissues. C4.4A expression in human cancer has rarely been evaluated. Thus, it became important to explore C4.4A protein expression in human tumour tissue to obtain an estimate on the frequency of expression and the correlation with tumour progression, the study focusing on colorectal cancer. The analysis of C4.4A in human tumour lines by western blot and immunoprecipitation using polyclonal rabbit antibodies that recognize different C4.4A epitopes revealed C4.4A oligomer and heavily glycosylated C4.4A isoform expression that, in some instances, inhibited antibody binding and interaction with the C4.4A ligand galectin-3. In addition, tumour cell lines released C4.4A by vesicle shedding and proteolytic cleavage. C4.4A was expressed in over 80% of primary colorectal cancer and liver metastasis with negligible expression in adjacent colonic mucosa, inflamed colonic tissue and liver. This compares well with EpCAM and CO-029 expression in over 90% of colorectal cancer. C4.4A expression was only observed in about 50% of pancreatic cancer and renal cell carcinoma. By de novo expression in colonic cancer tissue, we consider C4.4A as a candidate diagnostic marker in colorectal cancer, which possibly can be detected in body fluids.

Cytochrome c oxidase deficiency due to mutations in SCO2, encoding a mitochondrial copper-binding protein, is rescued by copper in human myoblasts.

Mutations in SCO2, a cytochrome c oxidase (COX) assembly gene, have been reported in nine infants with early onset fatal cardioencephalomyopathy and a severe COX deficiency in striated muscle. Studies on a yeast homolog have suggested that human Sco2 acts as a copper chaperone, transporting copper to the Cu(A) site on the Cox II subunit, but the mechanism of action remains unclear. To investigate the molecular basis of pathogenesis of Sco2 defects in humans we performed genetic and biochemical studies on tissues, myoblasts and fibroblasts from affected patients, as well as on a recombinant human C-terminal Sco2 segment (22 kDa), bearing the putative CxxxC metal-binding motif. Recombinant Sco2 was shown to bind copper with a 1:1 stoichiometry and to form homomeric complexes in vitro, independent of the metal-binding motif. Immunohistochemistry using antibodies directed against different COX subunits showed a marked tissue-specific decrease in the Cox II/III subunits that form part of the catalytic core, consistent with the differential tissue involvement, but a more uniform distribution of Cox Vab, a nuclear-encoded subunit. Sco2 was severely reduced in patient fibroblasts and myoblasts by immunoblot analysis. Patient fibroblasts showed increased (64)Cu uptake but normal retention values and, consistent with this, the copper concentration was four times higher in Sco2-deficient myoblasts than in controls. COX activity in patient myoblasts was completely rescued by transduction with a retroviral vector expressing the human SCO2 coding sequence, and more interestingly by addition of copper-histidine (300 microM) to the culture medium. Whether the latter is accomplished by the very low residual levels of Sco2 in the patient cells, direct addition of copper to the Cu(A) site, or by another copper-binding protein remains unknown. Whatever the mechanism, this result suggests a possible therapy for the early treatment of this fatal infantile disease.

The P(174)L mutation in the human hSCO1 gene affects the assembly of cytochrome c oxidase.

Mutations of the yeast SCO1 gene result in impaired COX assembly. Recently, heterozygous mutations in the human homologue hSCO1 have been reported in infants suffering from neonatal ketoacidotic coma and isolated COX deficiency (Valnot et al., 2000). One of the hSCO1 alleles harboured a frame shift mutation resulting in a premature stop codon, the other a missense mutation leading to a substitution of proline(174) by leucine. This position is next to the essential CXXXC motif, which is conserved in all Sco1p homologues. We used chimeric proteins with the amino-terminal portion derived from yeast Sco1p and carboxy-terminal portion including the CXXXC motif from the human hSco1p to provide experimental evidence for the pathogenic nature of the P(174)L mutation. These chimeras are able to complement yeast sco1 null mutants. Introduction of the P(174)L mutation affects the function of these chimeric proteins severely, as shown by impaired COX assembly and loss of COX activity.

Mitochondrial copper metabolism in yeast: interaction between Sco1p and Cox2p.

Yeast mitochondrial Sco1p is required for the formation of a functional cytochrome c oxidase (COX). It was suggested that Sco1p aids copper delivery to the catalytic center of COX. Here we show by affinity chromatography and coimmunoprecipitation that Sco1p interacts with subunit Cox2p. In addition we provide evidence that Sco1p can form homomeric complexes. Both homomer formation and binding of Cox2p are neither dependent on the presence of copper nor affected by mutations of His-239, Cys-148 or Cys-152. These amino acids, which are conserved among the members of the Sco1p family, have been suggested to act in the reduction of the cysteines in the copper binding center of Cox2p and are discussed as ligands for copper.

Identification of functionally important regions of the Saccharomyces cerevisiae mitochondrial translational activator Cbs1p.

Translation of cytochrome b mRNA in yeast mitochondria requires activation by the nuclear-encoded Cbs1p. According to the current model, Cbs1p tethers cytochrome b mRNA to the inner mitochondrial membrane via interaction with the 5'-untranslated leader. Cbs1p is predicted to be a hydrophilic protein with two hydrophobic segments near the carboxyl-terminal end, which are both too short to span the membrane. Nevertheless Cbs1p is tightly associated with the mitochondrial membrane, as shown by its behaviour in extraction experiments with taurodeoxycholate. In an attempt to define functionally important regions of Cbs1p, we created a number of mutant alleles by random and directed mutagenesis. We report that a Cbs1p mutant protein lacking the mitochondrial presequence is still able to complement a Deltacbs1 strain, suggesting that the presequence does not contain essential mitochondrial targeting information. Mutations in a cluster of positively charged amino acids at the extremeC-terminus have no effect on Cbs1p function, but removal of this segment severely impairs Cbs1p function. Truncation of 12 or more amino acids from the C-terminus results in a completely defective protein. We further show that both short hydrophobic regions are essential for Cbs1p function, although membrane association is observed even in the absence of these regions.

Human members of the SCO1 gene family: complementation analysis in yeast and intracellular localization.

Cytochrome c oxidase is a multiprotein complex in the mitochondrial membrane whose biogenesis requires a number of proteins besides the structural subunits. Several yeast proteins as well as a human disease-related protein have been reported which are involved in cytochrome c oxidase assembly. The S. cerevisiae Sco1p protein has been implicated in the transfer of copper to cytochrome c oxidase subunits Cox1p and/or Cox2p. Here we report on the complementation behavior in yeast of two recently identified ScSco1p homologs of chromosome 17 and chromosome 22 from human. When allotropically expressed in yeast, both genes fail to complement the lack of the ScSCO1 gene. However, a chimera of the N-terminal half of ScSco1p and the C-terminal half of the chromosome 17 homolog does substitute for the ScSco1p function. Interestingly, the respective chimera with the human homolog of chromosome 22 is not able to complement. Expression of EGFP fusions in HeLa cells shows that both human ScSco1p homologs are located in the mitochondria of human cells.

Acetabular labrum: MRI in asymptomatic volunteers.

PURPOSE: The purpose of this study was to describe the MR appearance of the acetabular labrum in asymptomatic hips on high resolution MRI. METHOD: Fifty-two hips in 46 asymptomatic volunteers with an age range of 15-85 years were evaluated with coronal and axial T1-weighted and T2-weighted sequences. The shape, margin, size, and signal intensity of the acetabular labrum were analyzed. RESULTS: The labrum was absent in its anterosuperior aspect in five hips (10%). Intralabral regions of intermediate of high signal intensity were detected in 30 hips (58%) imaged with T1-weighted and proton density-weighted sequences. Intralabral linear hyperintense foci reaching the articular surface and consistent with a labral tear were detected in four labra on T2-weighted images. Intralabral microcysts were seen in three labra. CONCLUSION: The MR appearance of the hip labrum is varied in asymptomatic volunteers. Intralabral increased signal intensity and absent anterosuperior labra are especially frequent and may represent asymptomatic lesions or normal variations.