Subunit interactions of the disease-related hexameric GlcNAc-1-phosphotransferase complex.

The multimeric GlcNAc-1-phosphotransferase complex catalyzes the formation of mannose 6-phosphate recognition marker on lysosomal enzymes required for receptor-mediated targeting to lysosomes. GNPTAB and GNPTG encode the α/β-subunit precursor membrane proteins and the soluble γ-subunits, respectively. Performing extensive mutational analysis, we identified the binding regions of γ-subunits in a previously uncharacterized domain of α-subunits comprising residues 535-698, named GNPTG binding (GB) domain.

GORAB Missense Mutations Disrupt RAB6 and ARF5 Binding and Golgi Targeting.

Gerodermia osteodysplastica is a hereditary segmental progeroid disorder affecting skin, connective tissues, and bone that is caused by loss-of-function mutations in GORAB. The golgin, RAB6-interacting (GORAB) protein localizes to the Golgi apparatus and interacts with the small GTPase RAB6. In this study, we used different approaches to shed more light on the recruitment of GORAB to this compartment.

Missense variant in CCDC22 causes X-linked recessive intellectual disability with features of Ritscher-Schinzel/3C syndrome.

Ritscher-Schinzel syndrome (RSS)/3C (cranio-cerebro-cardiac) syndrome (OMIM#220210) is a rare and clinically heterogeneous developmental disorder characterized by intellectual disability, cerebellar brain malformations, congenital heart defects, and craniofacial abnormalities. A recent study of a Canadian cohort identified homozygous sequence variants in the KIAA0196 gene, which encodes the WASH complex subunit strumpellin, as a cause for a form of RSS/3C syndrome. We have searched for genetic causes of a phenotype similar to RSS/3C syndrome in an Austrian family with two affected sons.

Transplantation of human umbilical cord blood cells mediated beneficial effects on apoptosis, angiogenesis and neuronal survival after hypoxic-ischemic brain injury in rats.

Transplantation of human umbilical cord blood (hucb) cells in a model of hypoxic-ischemic brain injury led to the amelioration of lesion-impaired neurological and motor functions. However, the mechanisms by which transplanted cells mediate functional recovery after brain injury are largely unknown. In this study, the effects of hucb cell transplantation were investigated in this experimental paradigm at the cellular and molecular level.

A key enzyme in the biogenesis of lysosomes is a protease that regulates cholesterol metabolism.

Mucolipidosis II is a severe lysosomal storage disorder caused by defects in the α and β subunits of the hexameric N-acetylglucosamine-1-phosphotransferase complex essential for the formation of the mannose 6-phosphate targeting signal on lysosomal enzymes. Cleavage of the membrane-bound α/β-subunit precursor by an unknown protease is required for catalytic activity. Here we found that the α/β-subunit precursor is cleaved by the site-1 protease (S1P) that activates sterol regulatory element-binding proteins in response to cholesterol deprivation.

Proteolytic processing of the gamma-subunit is associated with the failure to form GlcNAc-1-phosphotransferase complexes and mannose 6-phosphate residues on lysosomal enzymes in human macrophages.

GlcNAc-1-phosphotransferase is a Golgi-resident 540-kDa complex of three subunits, alpha(2)beta(2)gamma(2), that catalyze the first step in the formation of the mannose 6-phosphate (M6P) recognition marker on lysosomal enzymes. Anti-M6P antibody analysis shows that human primary macrophages fail to generate M6P residues. Here we have explored the sorting and intracellular targeting of cathepsin D as a model, and the expression of the GlcNAc-1-phosphotransferase complex in macrophages.

Mannose phosphorylation in health and disease.

Lysosomal hydrolases catalyze the degradation of a variety of macromolecules including proteins, carbohydrates, nucleic acids and lipids. The biogenesis of lysosomes or lysosome-related organelles requires a continuous substitution of soluble acid hydrolases and lysosomal membrane proteins. The targeting of lysosomal hydrolases depends on mannose 6-phosphate residues (M6P) that are recognized by specific receptors mediating their transport to an endosomal/prelysosomal compartment.

The chemokine SDF-1/CXCL12 contributes to the 'homing' of umbilical cord blood cells to a hypoxic-ischemic lesion in the rat brain.

Previous studies have shown that transplanted human umbilical cord blood (hUCB)-derived mononuclear cells exert therapeutic effects in various animal models of CNS impairments, including those of perinatal hypoxic-ischemic brain injury. However, the mechanisms of how transplanted cells exert their beneficial effects on the damaged tissue are still unclear. As detection of hUCB cells at the lesion site coincides with the therapeutic effects observed in our model, we investigated the role of the chemokine stromal derived factor (SDF)-1 (CXCL12) as a possible candidate for chemotaxis-mediated 'homing' of transplanted hUCB cells to a hypoxic-ischemic lesion in the perinatal rat brain.

Glycosylation- and phosphorylation-dependent intracellular transport of lysosomal hydrolases.

Lysosomes contain more than 50 soluble hydrolases that are targeted to lysosomes in a mannose 6-phosphate (Man6P)-dependent manner. The phosphorylation of man- nose residues on high mannose-type oligosaccharides of newly synthesized lysosomal enzymes is catalyzed by two multimeric enzymes, GlcNAc-1-phosphotransferase and GlcNAc-1-phosphodiester-alpha-N-acetylglucosaminidase, allowing the binding to two distinct Man6P receptors in the Golgi apparatus. Inherited defects in the GlcNAc-1-phosphotransferase complex result in missorting and cellular loss of lysosomal enzymes, and the subsequent lysosomal dysfunction causes the lysosomal storage disorders mucolipidosis types II and III.