The human cytochrome c oxidase assembly factors SCO1 and SCO2 have regulatory roles in the maintenance of cellular copper homeostasis

Human SCO1 and SCO2 are metallochaperones that are essential for the assembly of the catalytic core of cytochrome c oxidase (COX). Here we show that they have additional, unexpected roles in cellular copper homeostasis. Mutations in either SCO result in a cellular copper deficiency that is both tissue and allele specific. This phenotype can be dissociated from the defects in COX assembly and is suppressed by overexpression of SCO2, but not SCO1. Overexpression of a SCO1 mutant in control cells in which wild-type SCO1 levels were reduced by shRNA recapitulates the copper-deficiency phenotype in SCO1 patient cells. The copper-deficiency phenotype reflects not a change in high-affinity copper uptake but rather a proportional increase in copper efflux. These results suggest a mitochondrial pathway for the regulation of cellular copper content that involves signaling through SCO1 and SCO2, perhaps by their thiol redox or metal-binding state.     

Inhibition of monoamine oxidase by amiloride

Amiloride was found to lower the overflow of 3,4-dihydroxyphenylethylene glycol from isolated rat tail artery. The overflow was reduced to about 50% in the presence of 10(-5) M concentration of the drug. Reduced overflows of the glycol were observed also under conditions when the nonexocytotic release of endogenous noradrenaline was enhanced by tyramine, reserpine, or by the elevation of external K+ in the absence of extracellular Ca2+. They were accompanied by increased overflows of the amine. Amiloride inhibited monoamine oxidase activity (E.C. 1.4.3.4) of the A form in rat brain homogenate by acting as a competitive inhibitor.     

Amiloride acts as an alpha-adrenergic antagonist in the isolated rat tail artery

In the final concentration of 100 microM, amiloride increased substantially the overflow of endogenous noradrenaline and decreased that of 3,4-dihydroxyphenylethylene glycol from the rat tail artery into Krebs solution supplemented with 10 microM veratridine. The overflow of the amine into a 120 mM-K version of Krebs solution was unaffected by amiloride, while that of the glycol was reduced. Abolition of the contractile response to 10 microM veratridine by 2 microM phentolamine indicated that the response was due to release of endogenous noradrenaline. Addition of amiloride in the final concentrations of 10 and 100 microM caused relaxation of strips contracted by the alkaloid. The dose-response relations for exogenous noradrenaline measured in the absence or presence of 50 microM amiloride indicated that the drug acted as a reversible competitive alpha-adrenergic antagonist. The phentolamine-resistant component of the contractile response to the 120 mM-K solution was unaffected by 100 microM amiloride. Although the exact site of action of amiloride remains to be determined, it can be concluded that amiloride inhibits adrenergic transmission at a postsynaptic site at a step preceding elevation of myoplasmic Ca2+.     

SEM analysis of dental enamel morphological structures on the basis of their replicas in patients with systemic calcium deficiency

The aim of the present study is to examine microscopically the surface of dental enamel by using a scanning electron microscope (SEM), using their replicas formed in female patients with diagnosed periodontal diseases and systemic calcium deficiency. Replicas of dental enamel surfaces in patients referred for treatment of periodontal diseases were subjected to microscopic analysis. The replicas, after coating with platinum-palladium alloy, were examined under the scanning electron microscope at magnifications of 15–5000 x. Densitometric examinations of spine (L₂ - L₄ segment) revealed bone mineral density BMD T-score lower than −2.5 in 5 patients, in the range of −1.5 to −2.5 in 10 patients, and higher than −1.5 in the remaining patients. Non-homogenous images of surfaces in the form of light and dark areas were observed. Light areas corresponded to damaged surfaces of dental tissues. Patients with higher systemic calcium deficiency had areas lighter in color. More of these areas were found in patients with higher systemic calcium deficiency. It can be assumed that the calcium deficit is likely to appear in the selected dental tissues, particularly in the dental enamel.     

Networking with mitogen-activated protein kinases

Mitogen activated protein (MAP) kinases and their target ribosomal protein S6 (RSK) kinases have been recognized as shared components in the intracellular signaling pathways of many diverse cytokines. Recent studies have extended this protein kinase cascade by identifying the major activator of vertebrate MAP kinases as a serine/threonine/tyrosine-protein kinase called MEK, which is related to yeast mating factor-regulated protein kinases encoded by the STE7 and byr1 genes. MEK, in turn, may be activated following its phosphorylation on serine by either of the kinases encoded by proto-oncogenesraf1 ormos, as well as by p78 ^mekk , which is related to the yeast STE11 and byr2 gene products. Isoforms of all of these protein kinases may specifically combine to assemble distinct modules for intracellular signal transmission. However, the fundamental architecture of these protein kinase cascades has been highly conserved during eukaryotic evolution.