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Biomedical subjects

Catherine Scott

Publications and source records attributed to Catherine Scott.

8 recordsLinked to original sources
PubMed2005

Inactivation of NPC1L1 causes multiple lipid transport defects and protects against diet-induced hypercholesterolemia.

NPC1L1, a recently identified relative of Niemann-Pick C1, was characterized to determine its subcellular location and potential function(s). NPC1L1 was highly expressed in HepG2 cells and localized in a subcellular vesicular compartment rich in the small GTPase Rab5. mRNA expression profiling revealed significant differences between mouse and man with highest expression found in human liver and significant expression in the small intestine. In contrast, liver expression in mouse was extremely low with mouse small intestine exhibiting the highest NPC1L1 expression. A mouse knock-out model of NPC1L1 was generated and revealed that mice lacking a functional NPC1L1 have multiple lipid transport defects. Surprisingly, lack of NPC1L1 exerts a protective effect against diet-induced hyperlipidemia. Further characterization of cell lines generated from wild-type and knock-out mice revealed that in contrast to wild-type cells, NPC1L1 cells exhibit aberrant plasma membrane uptake and subsequent transport of various lipids, including cholesterol and sphingolipids. Furthermore, lack of NPC1L1 activity causes a deregulation of caveolin transport and localization, suggesting that the observed lipid transport defects may be the indirect result of an inability of NPC1L1 null cells to properly target and/or regulate caveolin expression.

Animals↗
PubMed2004

The NPC1 protein: structure implies function.

Niemann-Pick type C (NPC) is a lysosomal storage disorder, characterized by intracellular accumulation of low-density lipoprotein (LDL)-derived cholesterol and neurodegeneration leading to premature death. The most common form of the disease, NPC1, results from mutations in the NPC1 gene. Thus, the NPC1 protein is the focus of intense investigation to elucidate the function of this protein and its role in the disease pathogenesis. Recent studies have revealed the NPC1 subcellular location, topology and potential functions of the NPC1 protein. In lieu of direct experimental evidence, certain hypotheses about the function of NPC1 can be inferred by analyzing disease-causing mutations, NPC1 protein sequence homology to other related proteins, and the potential tertiary structure similarity between NPC1 and its prokaryotic ancestors, such as the E. coli RND permease AcrB. This review will discuss recent work on the characterization and function of the NPC1 protein and highlight structural features that may be important in assisting in the elucidation of NPC1 function and role in subcellular lipid transport and homeostasis.

Amino Acid Sequence↗
PubMed2004

Targeting of NPC1 to late endosomes involves multiple signals, including one residing within the putative sterol-sensing domain.

The NPC1 protein is a multipass transmembrane protein whose deficiency causes the autosomal recessive lipid storage disorder Niemann-Pick type C1. NPC1 localizes predominantly to late endosomes and has a dileucine motif located within a small cytoplasmic tail thought to target the protein to this location. Our data have suggested previously that the protein can reach its correct location in the absence of its cytoplasmic tail, suggesting that other signals contribute to NPC1 targeting. By using various FLAG-tagged and CD32-NPC1 chimeric fusion constructs, we show that multiple signals are responsible for the trafficking of NPC1 to the endosomal compartment, including the dileucine motif and a previously unidentified signal residing within the putative sterol-sensing domain transmembrane domain 3. Neither region alone was capable of directing heterologous CD32 fusions to late endosomes exclusively via the trans-Golgi network to the late endosome route taken by wild-type NPC1; transmembrane domain 3 was unable to maintain CD32 in late endosomes, indicating that two or more signals work in concert to target and retain NPC1 in this compartment. In addition we confirm that the tail dileucine motif is not essential for NPC1 targeting to late endosomes, and we discuss the implications of this finding along with the previously unappreciated role for transmembrane domain 3 in NPC1 localization and function.

Amino Acid Sequence↗
PubMed2004

The seeds of Lotus japonicus lines transformed with sense, antisense, and sense/antisense galactomannan galactosyltransferase constructs have structurally altered galactomannans in their endosperm cell walls.

Galactomannan biosynthesis in legume seed endosperms involves two Golgi membrane-bound glycosyltransferases, mannan synthase and galactomannan galactosyltransferase (GMGT). GMGT specificity is an important factor regulating the distribution and amount of (1-->6)-alpha-galactose (Gal) substitution of the (1-->4)-beta-linked mannan backbone. The model legume Lotus japonicus is shown now to have endospermic seeds with endosperm cell walls that contain a high-Gal galactomannan (mannose [Man]/Gal = 1.2-1.3). Galactomannan biosynthesis in developing L. japonicus endosperms has been mapped, and a cDNA encoding a functional GMGT has been obtained from L. japonicus endosperms during galactomannan deposition. L. japonicus has been transformed with sense, antisense, and sense/antisense ("hairpin loop") constructs of the GMGT cDNA. Some of the sense, antisense, and sense/antisense transgenic lines exhibited galactomannans with altered (higher) Man/Gal values in their (T(1) generation) seeds, at frequencies that were consistent with posttranscriptional silencing of GMGT. For T(1) generation individuals, transgene inheritance was correlated with galactomannan composition and amount in the endosperm. All the azygous individuals had unchanged galactomannans, whereas those that had inherited a GMGT transgene exhibited a range of Man/Gal values, up to about 6 in some lines. For Man/Gal values up to 4, the results were consistent with lowered Gal substitution of a constant amount of mannan backbone. Further lowering of Gal substitution was accompanied by a slight decrease in the amount of mannan backbone. Microsomal membranes prepared from the developing T(2) generation endosperms of transgenic lines showed reduced GMGT activity relative to mannan synthase. The results demonstrate structural modification of a plant cell wall polysaccharide by designed regulation of a Golgi-bound glycosyltransferase.

Amino Acid Sequence↗
PubMed2004

Efficacy and safety of fluticasone propionate/salmeterol HFA 134A MDI in patients with mild-to-moderate persistent asthma.

The objective of this study was to compare the efficacy and safety of fluticasone propionate (FP) (44 microg)/salmeterol (21 microg) delivered as two inhalations twice daily via a single hydrofluoroalkane (HFA 134a) metered dose inhaler (MDI) (FSC) with that of placebo HFA 134a (PLA), fluticasone propionate 44 microg chlorofluorocarbon (CFC) alone and salmeterol 21 microg CFC alone (S) in patients (n=360) with persistent asthma previously treated with beta2-agonists (short- or long-acting) or inhaled corticosteroids (ICS). After 12 weeks of treatment, patients treated with FSC had a significantly greater increase (p < or = 0.006) in mean FEV1 AUC(bl) compared with PLA, FP, or S. At end point, mean change from baseline in morning predose FEV1 for FSC (0.58 L) was significantly (p < or = 0.004) greater than PLA (0.14 L), FP (0.36 L), and S (0.25 L). Patients treated with FSC also had a significantly higher probability of remaining in the study without being withdrawn due to worsening asthma (2%) compared with those in the PLA (29%) and S (25%) groups (p < 0.001). Finally, treatment with FSC resulted in significantly (p < or = 0.007) greater improvements in morning and evening peak expiratory flow, need for rescue albuterol, and asthma symptom scores compared with FP, S, and PLA. The safety profile of FSC was also similar to FP or S alone. Initial maintenance treatment of the two main components of asthma, inflammation, and smooth muscle dysfunction (e.g., bronchoconstriction), with FSC results in greater overall improvements in asthma control compared with treatment of either individual component alone.

Adolescent↗
PubMed2003

Efficacy and safety of fluticasone propionate 44 microg/salmeterol 21 microg administered in a hydrofluoroalkane metered-dose inhaler as an initial asthma maintenance treatment.

BACKGROUND: We wanted to evaluate whether treatment with an inhaled corticosteroid and an inhaled long-acting beta2-agonist is more effective than an inhaled corticosteroid alone for patients using as-needed albuterol who are initiating maintenance treatment. OBJECTIVE: To compare the efficacy and safety of twice-daily fluticasone propionate (FP) 88 microg and salmeterol 42 microg combined in a chlorofluorocarbon (CFC)-free (hydrofluoroalkane 134a) metered-dose inhaler (MDI) with the individual agents alone, each delivered through an MDI containing CFC propellants, in patient with persistent asthma previously uncontrolled with as-needed short-acting beta2-agonists alone. METHODS: Patients with asthma (n = 283) were randomized to twice-daily treatment for 12 weeks with FP 88 microg combined with salmeterol 42 microg (FSC) in a CFC-free MDI or the individual components alone from CFC-containing MDIs. RESULTS: At endpoint, mean change from baseline in morning predose forced expiratory volume in 1 second was significantly (P < or = 0.016) greater with FSC (0.69 L) compared with FP (0.51 L) or salmeterol (0.47 L). Fewer patients treated with FSC withdrew due to worsening asthma (1%) compared with FP (3%) or salmeterol (8%; P = 0.024). FSC significantly increased (P < or = 0.002) morning and evening peak expiratory flow rate at endpoint (66.5 and 51.5 L/min, respectively) compared with FP (43.0 and 29.9 L/min, respectively) and salmeterol (29.2 and 21.6 L/min, respectively). In addition, asthma symptom scores were reduced, and percentages of days with no asthma symptoms increased in all treatment groups. CONCLUSIONS: Treatment with FSC in a CFC-free MDI is more effective than FP or salmeterol alone in asthma patients who are symptomatic taking short-acting beta2-agonists alone.

Administration, Inhalation↗
PubMed2003

Tobacco transgenic lines that express fenugreek galactomannan galactosyltransferase constitutively have structurally altered galactomannans in their seed endosperm cell walls.

Galactomannans [(1-->6)-alpha-D-galactose (Gal)-substituted (1-->4)-beta-D-mannans] are major cell wall storage polysaccharides in the endosperms of some seeds, notably the legumes. Their biosynthesis in developing legume seeds involves the functional interaction of two membrane-bound glycosyltransferases, mannan synthase (MS) and galactomannan galactosyltransferase (GMGT). MS catalyzes the elongation of the mannan backbone, whereas GMGT action determines the distribution and amount of Gal substitution. Fenugreek (Trigonella foenum-graecum) forms a galactomannan with a very high degree of Gal substitution (Man/Gal = 1.1), and its GMGT has been characterized. We now report that the endosperm cell walls of the tobacco (Nicotiana tabacum) seed are rich in a galactomannan with a very low degree of Gal substitution (Man/Gal about 20) and that its depositional time course is closely correlated with membrane-bound MS and GMGT activities. Furthermore, we demonstrate that seeds from transgenic tobacco lines that express fenugreek GMGT constitutively in membrane-bound form have endosperm galactomannans with increased average degrees of Gal substitution (Man/Gal about 10 in T(1) generation seeds and about 7.5 in T(2) generation seeds). Membrane-bound enzyme systems from transgenic seed endosperms form galactomannans in vitro that are more highly Gal substituted than those formed by controls under identical conditions. To our knowledge, this is the first report of structural manipulation of a plant cell wall polysaccharide in transgenic plants via a biosynthetic membrane-bound glycosyltransferase.

Cell Wall↗