SNAP-25-associated Hrs-2 protein colocalizes with AQP2 in rat kidney collecting duct principal cells.

The vasopressin-induced trafficking of aquaporin-2 (AQP2) water channels in kidney collecting duct is likely mediated by vesicle-targeting proteins (N-ethylmaleimide-sensitive factor attachment protein receptors). Hrs-2 is an ATPase believed to have a modulatory role in regulated exocytosis. To examine whether Hrs-2 is expressed in rat kidney, we carried out RT-PCR combined with DNA sequence analysis and Northern blotting using a digoxigenin-labeled Hrs-2 RNA probe. RT-PCR and Northern blotting revealed that Hrs-2 mRNA is localized in all zones of rat kidney. The presence of Hrs-2 protein in rat kidney was confirmed by immunoblotting, revealing a 115-kDa protein in kidney and brain membrane fractions corresponding to the expected molecular size of Hrs-2. Immunostaining and confocal laser scanning microscopy of LLC-PK(1) cells (a porcine proximal tubule cell line) transfected with Hrs-2 DNA confirmed the specificity of the antibody and revealed that Hrs-2 is mainly localized in intracellular compartments, including cathepsin D-containing lysosomal/endosomal compartments. The cellular and subcellular localization of Hrs-2 in rat kidney was examined by immunocytochemistry and confocal laser scanning microscopy. Hrs-2 immunoreactivity was observed in collecting duct principal cells, and weaker labeling was detected in other nephron segments. The labeling was predominantly present in intracellular vesicles, but labeling was also observed in the apical plasma membrane domains of some cells. Colabeling with AQP2 revealed colocalization in vesicles and apical plasma membrane domains, suggesting a role for Hrs-2 in regulated AQP2 trafficking.

Chronic bullous dermatosis of childhood.

A study of 16 patients with chronic bullous dermatosis of childhood (CBDC) is reported. They were followed up for 0.5 to 4.5 years. Histological and immunofluorescent (IF) study of the skin and local provocation of skin lesions by Trafuril test were carried out in every case, intestinal biopsy in twelve cases. Four patients were found to have IgG, and three IgA, along the skin basement membrane. In nine patients, no immunoglobulins were detectable; these IF negative cases seemed to be pseudonegative. Repeated biopsy and immunoelectronmicroscopic study of the skin may be helpful. In the three patient groups classified on the basis of skin IF studies, there was no difference in the clinical and histological picture, in reaction to Trafuril test and in the result of treatment. The small intestinal mucosa was abnormal in three of twelve patients. A gluten-free diet introduced in two patients had no effect on the course of the disease. CBDC with negative or positive IF, juvenile pemphigoid and IgA linear dermatosis seem to be a common clinical entity, different in severity and with individual variations. The condition is not identical with dermatitis herpetiformis Duhring.