Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The post-transcriptional regulation of gene expression underlies several critical developmental phenomena. In metazoa, gene products that are expressed, silenced and packaged during oogenesis govern early developmental processes prior to nascent transcription activation. Furthermore, tissue-specific alternative splicing of several transcription factors controls pattern formation and organ development. A highly conserved family of proteins containing a STAR/GSG RNA-binding domain is essential to both processes. Here, we identify the consensus STAR-binding element (SBE) required for specific mRNA recognition by GLD-1, a key regulator of Caenorhabditis elegans germline development. We have identified and verified new GLD-1 repression targets containing this sequence. The results suggest additional functions of GLD-1 in X-chromosome silencing and early embryogenesis. The SBE is present in Quaking and How mRNA targets, suggesting that STAR protein specificity is highly conserved. Similarities between the SBE and the branch-site signal indicate a possible competition mechanism for STAR/GSG regulation of splicing variants.
Nat Struct Mol Biol 2004 Jan
PMID:RNA target specificity of the STAR/GSG domain post-transcriptional regulatory protein GLD-1. 1471 11

Proteins containing the STAR RNA-binding domain fulfill vital roles in RNA biogenesis, yet a detailed understanding of STAR domain RNA binding specificity is lacking. In Caenorhabditis elegans, the STAR protein GLD-1 directly binds the 28 nucleotide recognition element TGE within the 3' untranslated region of tra-2 mRNA. The GLD-1:TGE interaction promotes translational silencing of tra-2 mRNA, marking a pivotal event in the spermatogenesis to oogenesis switch in C.elegans hermaphrodites. By measuring the binding affinities of both GLD-1 and TGE mutants, we have explored the molecular determinants of STAR domain specificity. Site-directed GLD-1 mutants were guided by sequence homology with human splicing factor 1 (SF1), for which an RNA:protein complex structure is available in the work done by Liu et al. The RNA binding affinity of 11 mutant GLD-1 proteins was measured, and their binding specificity was assessed with a series of TGE RNAs containing natural or modified nucleotides. This combinatorial analysis of both RNA and protein mutants revealed a diverse array of specificities of individual nucleotide-binding pockets along the interface. At nucleotide position 18, adenosine appears to be specified by the overall shape of a pocket lined with aliphatic side-chains. At position 19, the high preference for cytidine is dependent on both the length of an amino acid side-chain and the identity of terminal functional groups. The nucleotide 21 binding pocket exhibits low discrimination for cytidine, and accommodates most nucleobases. The highly hydrophobic binding interface and apparent small number of hydrogen bonding read-out interactions at these positions is consistent with our finding that few amino acids seem to function individually in establishing binding specificity. Rather, specificity is conferred by the shape of the nucleotide-binding pocket. Our data provide the first detailed, quantitative analysis of the STAR domain, and highlight features of STAR:RNA recognition that are distinct among single-stranded RNA-binding proteins.
J Mol Biol 2005 Feb 11
PMID:Shape-specific nucleotide binding of single-stranded RNA by the GLD-1 STAR domain. 1566 30

A six-month-old infant girl presenting with progressive encephalopathy and abnormal myelination in the cerebral white matter was originally diagnosed as suffering from Krabbe disease. The diagnosis was based on a deficiency of galactocerebrosidase activity found in leukocytes isolated from whole blood. When cultured skin fibroblasts did not show a similar enzyme deficiency and sulphatide (stearoyl-1-14C) uptake indicated an abnormal storage of galactosylceramide, a deficiency of an activator was implied. A three base pair deletion was found in the saposin A coding sequence of the prosaposin gene leading to the deletion of a conserved valine at amino acid number 11 of the saposin A protein. This deletion in saposin A is proposed as the cause for the abnormal galactosylceramide metabolism in this infant. This is the first report of a saposin A mutation in humans leading to pathological consequences.
Mol Genet Metab 2005 Feb
PMID:A mutation in the saposin A coding region of the prosaposin gene in an infant presenting as Krabbe disease: first report of saposin A deficiency in humans. 1577 42

Globoid cell leukodystrophy (GLD, Krabbe disease) is a severe demyelinating disease caused by a genetic defect of beta-galactocerebrosidase (GALC). To date treatment to GLD is limited to hematopoietic stem cell transplantation. Experimental approaches by means of gene therapy in twitcher mouse, an authentic murine model of human GLD, showed significant but only marginal improvements of the disease. To clarify whether the introduction of GALC could provide beneficial effects on the oligodendrocytes in GLD, we transduced twitcher oligodendrocytes by stereotactically injecting recombinant retrovirus encoding GALC-myc-tag fusion gene into the forebrain subventricular zone of neonatal twitcher mouse. In vivo effects of exogenous GALC on twitcher oligodendrocytes were studied histologically by combined immunostaining for the myc-epitope and the oligodendroglial specific marker, pi form of glutathione-S-transferase, at around 40 days of age. We show here that GALC transduction led to dramatic morphological improvement of the twitcher oligodendrocytes comparing with those in untreated twitcher controls. This study provided direct in vivo evidence that GALC transduction could prevent or correct aberrant morphology of oligodendrocytes in GLD which may be closely related to the dysfunction and/or degeneration of oligodendrocytes and the demyelination in this disease.
Mol Genet Metab 2005 Apr
PMID:GALC transduction leads to morphological improvement of the twitcher oligodendrocytes in vivo. 1578 Nov 94

The Quaking protein belongs to the family of STAR/GSG domain RNA-binding proteins and is involved in multiple cell signalling and developmental processes in vertebrates, including the formation of myelin. Heteronuclear NMR methods were used to determine the solution structure of a 134 residue fragment spanning the KH and QUA2 homology regions of the Quaking protein from Xenopus laevis (pXqua) in the absence of RNA. The protein is shown to adopt an extended type I KH domain fold that is connected to a structured alpha-helix in the C-terminal QUA2 region by means of a highly flexible linker. A comparison with the solution structure of the related protein splicing factor 1 (SF1) indicates that most aspects of the RNA-binding interface are conserved in pXqua, although the "variable loop" region that follows the second beta-strand possesses two additional alpha-helices. The structure of pXqua provides an appropriate template for building models of important homologues, such as GLD-1 and Sam68. Measurements of the (15)N relaxation parameters of pXqua confirm that the polypeptide backbone of the QUA2 region is more dynamic than that of the KH portion, and that the C-terminal helix is partially structured in the absence of RNA. By comparison with a random coil reference state, the nascent structure in the QUA2 region is estimated to contribute 15.5kJmol(-1) to the change in conformational free energy that occurs on forming a complex with RNA. Since STAR/GSG proteins may regulate alternative splicing by competing with SF1 in the nucleus for specific branch-point sequences that signal intronic RNA, the formation of secondary structure in the QUA2 region in the unbound state of pXqua has important functional consequences.
J Mol Biol 2005 Apr 29
PMID:Solution structure and backbone dynamics of the KH-QUA2 region of the Xenopus STAR/GSG quaking protein. 1581 67

Globoid cell leukodystrophy (GLD) or Krabbe disease is a neurodegenerative disorder caused by a deficiency of galactocerebrosidase (GALC) activity. GALC is required for the lysosomal degradation of galactosylceramide, psychosine, and possibly other galactolipids. This process is extremely important during active myelination. In the absence of functional GALC, psychosine accumulates, resulting in the apoptotic death of myelin-producing cells. While most patients are infants who do not survive beyond 2 years of age, some older patients are also diagnosed. Hematopoietic stem cell transplantation has proven to have a positive effect on the course of some patients with late-onset Krabbe disease. Murine models of this disease provide an excellent opportunity to evaluate therapeutic alternatives including gene therapy. In this study we used serotype 1 AAV to express mouse GALC under the control of the human cytomegalovirus promoter. Direct administration of these viral particles into the brains of neonatal mice with GLD resulted in sustained expression of GALC activity, improved myelination, attenuated symptoms, and prolonged life span. While this treatment also resulted in significant pathological improvements, the treated mice died with symptoms similar to those of the untreated mice. Additional initiatives may be required to prevent the onset of disease and reverse the course of the disease in animal models and human patients.
Mol Ther 2005 May
PMID:AAV-mediated expression of galactocerebrosidase in brain results in attenuated symptoms and extended life span in murine models of globoid cell leukodystrophy. 1585 Oct 12

Globoid cell leukodystrophy (GLD) is a disorder of the central and peripheral nervous systems caused by the deficiency of the lysosomal enzyme galactocerebrosidase (GALC). The pathological changes associated with the disease include accumulation of globoid cells and loss of myelin due to production of psychosine, a toxic metabolite responsible for the apoptosis of oligodendrocytes. While most patients present with symptoms before 6 months of age, older patients are also diagnosed. Treatment at this time is limited to hematopoietic stem cell transplantation in asymptomatic and late-onset patients. GLD occurs naturally in several animal species including mice, dogs, and monkeys. In addition, a transgenic (trs) mouse model of GLD was generated in our laboratory. Trs mice develop symptoms slower than twitcher mice and survive an average of 10 days longer. In this study, we evaluated the therapeutic effects of bone marrow transplantation (BMT) using trs mice. BMT prolonged the life of some treated animals to over one year. After BMT, GALC activity reached 15-20% of normal in brain and near normal values in liver and sciatic nerve. In long-lived transplanted animals psychosine levels were normalized in the brain and greatly reduced in the sciatic nerve. Staining of brain sections showed more abundant and better quality myelin and near absence of globoid cells. Electron micrographs of sciatic nerves showed reduced endoneurial edema, increased axon density, and abundant onion bulb structures associated with remyelinating axons. Therefore, BMT can ameliorate many of the biochemical and pathological features of GLD. However, additional therapies may be required to completely correct the features of this disease.
Mol Genet Metab
PMID:Biochemical and pathological evaluation of long-lived mice with globoid cell leukodystrophy after bone marrow transplantation. 1616 69

Psychosine (galactosylsphingosine) is a toxic metabolite that accumulates in globoid cell leukodystrophy (GLD) due to the deficiency of galactocerebrosidase (GALC) activity. This results in subsequent programmed cell death of oligodendrocytes and demyelination in human patients and animal models. We investigated the potential role of insulin-like growth factor-1 (IGF-1) in modifying the apoptotic effect of psychosine in cultured mouse oligodendrocyte progenitor cells (OLP-II). We show that psychosine inhibits the phosphorylation of Akt and Erk1/Erk2 (Erk1/2), which are the main anti-apoptotic pathways of the IGF-1 receptor (IGF-1R). Although IGF-1 sustained phosphorylation of both of these pathways, it provided maximum protection to OLP-II cells from psychosine-induced cell death in a PI3K/Akt-dependent manner. The effects of IGF-1 were dose-dependent and resulted in increased IGF-1R autophosphorylation levels. Although relatively high concentrations of IGF-1 also resulted in the activation of the insulin receptor (IR), its effect was more significant on the IGF-1R.
Mol Cell Neurosci 2005 Nov
PMID:Insulin-like growth factor-1 provides protection against psychosine-induced apoptosis in cultured mouse oligodendrocyte progenitor cells using primarily the PI3K/Akt pathway. 1616 44

Saposin A (Sap-A) is one of five known sphingolipid activator proteins required for the lysosomal degradation of sphingolipids and for the loading of lipid antigens onto antigen-presenting molecules of the CD1 type. Sap-A assists in the degradation of galactosylceramide by galactosylceramide-beta-galactosidase in vivo, which takes place at the surface of intraendosomal/intralysosomal vesicles. Sap-A is believed to mediate the interaction between the enzyme and its membrane-bound substrate. Its dysfunction causes a variant form of Krabbe disease. In the present study we prepared glycosylated Sap-A free of other Saps, taking advantage of the Pichia pastoris expression system. Using liposomes and surface plasmon resonance spectroscopy, we tested the binding and lipid mobilization capacity of Sap-A under different conditions. Along the endocytic pathway, the pH value decreases, and the lipid composition of intraendosomal and intralysosomal membranes changes drastically. In the inner membranes the cholesterol concentration decreases, and that of the anionic phospholipid bis(monoacylglycero)phosphate increases. Here, we show that Sap-A is able to bind to liposomes and to mobilize lipids out of them at acidic pH values below pH 4.7. Low cholesterol levels and increasing concentrations of bis(monoacylglycero)phosphate favor lipid extraction significantly. Galactosylceramide as a bilayer component is not essential for lipid mobilization by Sap-A, which requires intact disulfide bridges for activity. We also show for the first time that glycosylation of Sap-A is essential for its lipid extraction activity. Variant Sap-A proteins, which cause storage of galactosylceramide in humans (Krabbe disease, Spiegel, R., Bach, G., Sury, V., Mengistu, G., Meidan, B., Shalev, S., Shneor, Y., Mandel, H., and Zeigler, M. (2005) Mol. Genet. Metab. 84, 160-166) and in mutant mice (Matsuda, J., Vanier, M. T., Saito, Y., Tohyama, J., and Suzuki, K. (2001) Hum. Mol. Genet. 10, 1191-1199) are deficient in lipid extraction capacity.
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PMID:Saposin A mobilizes lipids from low cholesterol and high bis(monoacylglycerol)phosphate-containing membranes: patient variant Saposin A lacks lipid extraction capacity. 1690 46

This chapter describes in detail a practical procedure for the preparation of radiolabeled galactocerebroside and its use in the assay of galactocerebrosidase (GalCase), the enzyme deficient in globoid cell leukodystrophy (Krabbe disease). The reference range for leukocytes and fibroblasts is 0.9-4.4 and 8-36 nmoles substrate hydrolyzed per hour per milligram of protein, respectively. Because of its low abundance this enzyme is difficult to assay in certain situations, such as prenatal diagnosis by chorionic villus sampling. To obviate this a modified assay is used where only the radiolabeled substrate is included in the incubation. This provides a clear separation between affected samples and unaffected controls. The methods detailed here should be reproducible in any laboratory.
Methods Mol Biol 2006
PMID:Diagnosis of Krabbe disease by use of a natural substrate. 1707 20


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