A mitochondrial DNA deletion presenting with corneal clouding and severe Fanconi syndrome.

Background: Mitochondrial cytopathies are a diverse group of disorders characterized by impaired mitochondrial energy production. Disease manifestations are protean and may include seemingly disparate findings.

Case Diagnosis/treatment: Here we report a 5-year-old girl with the uncommon pairing of bilateral corneal dystrophy requiring corneal transplantation and severe Fanconi syndrome recalcitrant to oral bicarbonate therapy necessitating intravenous supplementation.

Reduced phosphate transport in the renal proximal tubule cells in cystinosis is due to decreased expression of transporters rather than an energy defect.

Nephropathic cystinosis is an autosomal recessive disorder caused by mutations in the CTNS gene [1], which encodes for a transporter (cystinosin) responsible for cystine efflux from lysosomes. In cystinotic renal proximal tubules (RPTs), the defect in cystinosin function results in reduced reabsorption of solutes by apical Na(+)/solute cotransport systems, including the Na(+)/phosphate (Pi) cotransport system [2]. However the underlying molecular mechanisms are unknown, given the lack of an appropriate cellular model.

Recycling of peroxiredoxin IV provides a novel pathway for disulphide formation in the endoplasmic reticulum.

Disulphide formation in the endoplasmic reticulum (ER) is catalysed by members of the protein disulphide isomerase (PDI) family. These enzymes can be oxidized by the flavoprotein ER oxidoreductin 1 (Ero1), which couples disulphide formation with reduction of oxygen to form hydrogen peroxide (H(2)O(2)). The H(2)O(2) produced can be metabolized by ER-localized peroxiredoxin IV (PrxIV).

Targeting of renal proximal tubule Na,K-ATPase by salt-inducible kinase.

The renal proximal tubule (RPT) is a central locale for Na+ reabsorption, and blood pressure regulation. Na+ reabsorption in the RPT depends upon the Na,K-ATPase, which is controlled by a complex regulatory network, including Salt-Inducible Protein Kinase (SIK). SIKs are recently discovered members of the AMP-activated Protein Kinase (AMPK) family, which regulate salt homeostasis and metabolism in a number of tissues.

Regulation of renal proximal tubule Na-K-ATPase by prostaglandins.

Prostaglandins (PGs) play a number of roles in the kidney, including regulation of salt and water reabsorption. In this report, evidence was obtained for stimulatory effects of PGs on Na-K-ATPase in primary cultures of rabbit renal proximal tubule (RPT) cells. The results of our real-time PCR studies indicate that in primary RPTs the effects of PGE(2), the major renal PG, are mediated by four classes of PGE (EP) receptors.