De Barsy Research Articles

Niemann-Pick C1 Functions in Regulating Lysosomal Amine Content

Mutations in the late endosomal/lysosomal membrane protein Niemann-Pick C1 (NPC1) are known to cause a generalized block in retrograde vesicle-mediated transport, resulting in the hyper-accumulation of multiple lysosomal cargos. An important, yet often overlooked, category of lysosomal cargo includes the vast array of small molecular weight amine-containing molecules that are substrates for ion trapping in the highly acidic organelle lumen. We show here that the introduction of amine-containing molecules in lysosomes can significantly stimulate NPC1-mediated late endosome/lysosome fusion, and subsequently the secretion of lysosomal cargo. To illustrate the physiological importance of this NPC1-mediated transport pathway, we show that NPC1-deficient cells are more susceptible to the toxic effects of a lysosomotropic polyamine metabolite 3-aminopropanal. Moreover, NPC fibroblasts are shown to have higher levels of polyamine oxidase, an enzyme involved in the formation of 3-aminopropanal. Collectively, these findings provide strong support for a novel functional role for NPC1 and may also provide clues toward understanding NPC disease progression.

De Barsy syndrome: a review of the phenotype

De Barsy syndrome is a rare, autosomal recessive syndrome characterised by a progeria-like appearance with distinctive facial features and cutis laxa. Ophthalmological, orthopaedic and neurological abnormalities are also typically present. The syndrome was first described by de Barsy et al. in 1967 and since that time approximately 27 further cases have been reported worldwide. We present a case that demonstrates the typical clinical and histological features of de Barsy syndrome. A female infant, the second child of first-cousin parents from a multiply consanguineous family of Pakistani origin, presented at birth with growth retardation, cutis laxa and a progeria-like appearance. She had thin, overlapping fingers and adducted thumbs, blue sclerae, cloudy corneas and myopia. She has failed to thrive and has marked developmental delay and abnormal athetoid movements. During the first year of life she developed pectus excavatum and her facial appearance became more aged. To our knowledge there are no previous reports of de Barsy syndrome in individuals of Pakistani origin.

The Cyclophilin-like Domain of Ran-binding Protein-2 Modulates Selectively the Activity of the Ubiquitin-Proteasome System and Protein Biogenesis

The ubiquitin-proteasome system (UPS) plays a critical role in protein degradation. The 19S regulatory particle (RP) of the 26S proteasome mediates the recognition, deubiquitylation, unfolding, and channeling of ubiquitylated substrates to the 20S proteasome. Several subunits of the 19S RP interact with a growing number of factors. The cyclophilin-like domain (CLD) of Ran-binding protein-2 (RanBP2/Nup358) associates specifically with at least one subunit, S1, of the base subcomplex of the 19S RP, but the functional implications of this interaction on the UPS activity are elusive. This study shows the CLD of RanBP2 promotes selectively the accumulation of a subset of reporter substrates of the UPS, such as the ubiquitin (Ub)-fusion yellow fluorescent protein (YFP) degradation substrate, Ub(G76V)-YFP, and the N-end rule substrate, Ub-R-YFP. Conversely, the degradation of endoplasmic reticulum and misfolded proteins, and of those linked to UPS-independent degradation, is not affected by CLD. The selective effect of CLD on the UPS in vivo is independent of, and synergistic with, proteasome inhibitors, and CLD does not affect the intrinsic proteolytic activity of the 20S proteasome. The inhibitory activity of CLD on the UPS resides in a purported SUMO binding motif. We also found two RanBP2 substrates, RanGTPase-activating protein and retinitis pigmentosa GTPase regulator interacting protein-1alpha1, whose steady-state levels are selectively modulated by CLD. Hence, the CLD of RanBP2 acts as a novel auxiliary modulator of the UPS activity; it may contribute to the molecular and subcellular compartmentation of the turnover of properly folded proteins and modulation of the expressivity of several neurological diseases.

Cutis laxa with growth and developmental delay, wrinkly skin syndrome and gerodermia osteodysplastica: a report of two unrelated patients and a literature review

Two unrelated patients of different sexes are described, both presenting with congenital redundant skin (cutis laxa), growth deficiency, mental retardation and bone dystrophy. Parental consanguinity in both families and a more pronounced severity of the neurological disease in the male patient were present. Both patients were diagnosed in infancy as having De Barsy syndrome, but clinical follow-up revealed that the clinical picture was compatible with the diagnosis of cutis laxa with growth and developmental delay (CLGDD), gerodermia osteodysplastica (GO) and wrinkly-skin syndrome (WWS). It has recently been suggested that cutis laxa with growth and developmental delay, gerodermia osteodysplastica and wrinkly skin syndrome are the same condition. A review concerning this diagnosis is also presented.

New lethal disease involving type I and III collagen defect resembling geroderma osteodysplastica, De Barsy syndrome, and Ehlers-Danlos syndrome IV.

We describe the clinical findings and biochemical features of a male child suffering from a so far undescribed lethal connective tissue disorder characterised by extreme hypermobility of the joints, lax...

Influence of conversion of penicillin G into a basic derivative on its accumulation and subcellular localization in cultured macrophages.

beta-Lactam antibiotics do not accumulate in phagocytes, probably because of their acidic character. We therefore synthesized a basic derivative of penicillin G, namely, 14C-labeled N-(3-dimethylamino-propyl)benzylpenicillinamide (ABP), and studied its uptake and subcellular localization in J774 macrophages compared with that of 14C-labeled penicillin G. Whereas the intracellular concentration (Ci) of penicillin G remained lower than its extracellular concentration (Ce), ABP reached a Ci/Ce ratio of 4 to 5. Moreover, approximately 50% of intracellular ABP was found associated with lysosomes after isopycnic centrifugation of cell homogenates in isoosmotic Percoll or hyperosmotic sucrose gradients. The behavior of ABP was thus partly consistent with the model of de Duve et al. (C. de Duve, T. de Barsy, B. Poole, A. Trovet, P. Tulkens, and A. Van Hoof, Biochem. Pharmacol. 23:2495-2531, 1974), in which they described the intralysosomal accumulation of weak organic bases in lysosomes. Although ABP is microbiologically inactive, our results show that beta-lactam antibiotics can be driven into cells by appropriate modification. Further efforts therefore may be warranted in the design of active compounds or prodrugs that may prove useful in the chemotherapy of intracellular infections.

De Barsy syndrome?an autosomal recessive, progeroid syndrome

We report two families with seven siblings with de Barsy syndrome. Characteristic features include severe mental retardation, hypermobility with athetoid movements, grimacing, muscular hypotonia, laxity of small joints and brisk deep tendon reflexes, progeroid aspect with cutis laxa, atrophy of skin with hyperpigmentation, isolated depigmentations, reduction of subcutaneous fatty tissue, translucent vein pattern, short stature, frontal bossing in the young child, large prominent ears with dysplastic helices and corneal clouding or cataracts. The syndrome probably has autosomal recessive inheritance.