The molecular defect leading to Fabry disease: structure of human alpha-galactosidase

Fabry disease is an X-linked lysosomal storage disease afflicting 1 in 40,000 males with chronic pain, vascular degeneration, cardiac impairment, and other symptoms. Deficiency in the lysosomal enzyme alpha-galactosidase (alpha-GAL) causes an accumulation of its substrate, which ultimately leads to Fabry disease symptoms. Here, we present the structure of the human alpha-GAL glycoprotein determined by X-ray crystallography. The structure is a homodimer with each monomer containing a (beta/alpha)8 domain with the active site and an antiparallel beta domain. N-linked carbohydrate appears at six sites in the glycoprotein dimer, revealing the basis for lysosomal transport via the mannose-6-phosphate receptor. To understand how the enzyme cleaves galactose from glycoproteins and glycolipids, we also determined the structure of the complex of alpha-GAL with its catalytic product. The catalytic mechanism of the enzyme is revealed by the location of two aspartic acid residues (D170 and D231), which act as a nucleophile and an acid/base, respectively. As a point mutation in alpha-GAL can lead to Fabry disease, we have catalogued and plotted the locations of 245 missense and nonsense mutations in the three-dimensional structure. The structure of human alpha-GAL brings Fabry disease into the realm of molecular diseases, where insights into the structural basis of the disease phenotypes might help guide the clinical treatment of patients.     

Changes in the Fatty Acid Composition of the Marine Ciliated Protozoan Parauronema acutum with Increasing Culture Age and Adaptation to Changing Sodium Chloride Concentrations

Changes in the fatty acid composition of the membrane lipids of the marine ciliate. Parauronema acutum were studied in ciliates harvested from early logarithmic, decelerating logarithmic and stationary phase culture. The relative amounts of 18:1 (9) and 18:2 (9, 12) decreases in both the phospholipid and the neutral sphingolipid fractions with increasing culture age. The content of 18:4 (6, 9, 12, 15), 20:5 (5, 8, 11, 14, 17) and 22:6 (4, 7, 10, 13, 16, 19) in these same lipids increases with culture age. While P. acutum was isolated as a marine ciliate and is usually grown in a medium containing 2.8% NaCl concentration, it actually grows well over NaCl concentration of 1% to 3% and will grow suboptimally without added NaCl. NaCl concentrations above 3% are inhibitory, although suboptimal growth occurs at 5% NaCl concentration. Lipids obtained from ciliates grown at either 1.5% or 2.8% NaCl have essentially identical FAME profiles. Lipids obtained from ciliates grown at either higher or lower concentrations of NaCl show marked changes in FAME profile. In both cases 18:2 (9, 12) content greatly increases while the content of 18 and 20 carbon highly unsaturated fatly acids, particularly 22:6 (4, 7, 10, 13, 16, 19), decreases.     

Extended use of a selective inhibitor of acid lipase for the diagnosis of Wolman disease and cholesteryl ester storage disease

Lysosomal acid lipase (LAL) deficiency produces two well defined inborn disorders, Wolman disease (WD) and cholesteryl ester storage disease (CESD). WD is a severe, early-onset condition involving massive storage of triglycerides and cholesteryl esters in the liver, with death usually occurring before one year of life. CESD is a more attenuated, later-onset disease that leads to a progressive and variable liver dysfunction. Diagnosis of LAL deficiency is mainly based on the enzyme assay of LAL activity in fibroblasts. Recently, a selective acid lipase inhibitor was used for the determination of enzyme activity in dried-blood filter paper (DBFP) samples. To extend and to validate these studies, we tested LAL activity with selective inhibition on DBFP samples, leukocytes and fibroblasts. Our results showed a clear discrimination between patients with LAL deficiency and healthy controls when using DBFP, leukocytes or fibroblasts (p < 0.001). Deficiency of LAL was also demonstrated in individuals referred to our laboratory with suspected clinical diagnosis of WD, CESD, and Niemann–Pick type B. We conclude that the assay of LAL using selective inhibitor is a reliable and useful method for the identification of LAL deficiency, not only in DBFP samples but also in leukocytes and fibroblasts. This is important as enzyme replacement therapy for LAL deficiency is currently being developed, making the correct diagnosis a critical issue.     

溶酶体贮积症和其他罕见疾病适应证治疗药物的相关交易情况

介绍汤森路透Cortellis 竞争情报分析数据库报道的市场上高额的溶酶体贮积症和其他罕见疾病治疗药物的合作协议以及该领域某些重要的有前景的候选治疗药物。     

Use of lissamine rhodamine ceramide trihexoside as a functional assay for alpha-galactosidase A in intact cells

Fabry disease is an X-linked disorder caused by mutations in the GLA gene encoding for α-galactosidase A (AGA, EC 3.2.1.22). Measurement of AGA enzyme activity using cell homogenates can easily identify men with Fabry disease, but in women, the degree of X-inactivation in the tested tissue may produce activities in homogenates that are indistinguishable from normal. Monti et al. developed a series of lissamine rhodamine-labeled glycosphingolipid substrates that can be used to measure clearance of these lipids in intact cells (1). We report here that one of these substrates, lissamine rhodamine ceramide trihexoside (LR-CTH), can be used as a probe for functional activity of AGA in intact fibroblasts, endothelial cells, and T-lymphocytes from patients with Fabry disease. By utilizing standard detection techniques, such as microscopic imaging, fluorescence microplate spectrophotometry, and flow cytometry, cells with impaired AGA activity can easily be distinguished from wild-type (WT) cells, and these two cell types can be isolated into separate populations using fluorescence-activated cell sorting (FACS). The assay we report here can be adapted to evaluate new therapies by high-throughput screening, can aid in the study of AGA activity in living cells, and can assist in the diagnosis of women with the Fabry trait.