The molecular basis of lysosomal storage diseases and their treatment

Abstract

By presenting the liver with lower collagenase exposure than for the isolation of conventional single hepatocytes (singlets), a preparation is obtained containing -20% of hepatocytes which have not separated from their neighhour at the junctional complex and thus remain as pairs (couplets. doublets) or small multiples; subsequent centrifugal clutriation can enrich the proportion of couplets to -70%.The junctions between the adjacent cells in the couplet are repaired during short-term (4-5h) culture; a sulcd canalicular vacuole is formed from the canalicular components of the two cells. Materials destined for bile can be pumped into this vacuole and accumulatc; the couplets are therefore polarized cells and are acting as rn wino models for the upper pan of the hepatobiliary system. Though possessing no advantage over singlets (indeed they are more difficult to obtain and use) for many metabolic and metabolic control applications couplets have, however, made substantial contributions to our understanding of polarized and hcpatobiliary aspects of hepatocytc function. Singlet hepatocytes have lost this polarity and are thus inappropriate for such studies. In addition to conventional biochemical techniques, work with hepatocyte couplets has made extensive use of visible and fluorescence microscopy, to elucidate: 1) discrimination of hepatounalicular from systemic or ductular effects on bile formation. 2) transcellular movements and canalicular destinations of fluorescent cholephilcs.3) recruitment of transporter molecules to the canalicular membrane and its control. 4) role, control and maturation of tight junctions sealing the bile canaliculus. 5) control and performance of gap junctions between hepatocytes. 6) distribution and control of the cytoskcleton in polarized hepatocytcs. 7) relative contributions of zonal hepatocytc functions in bile formation. 8)m vztro effects and mechanisms of action of cholestatic and hepatotoxic agents.In recent years much has been learned about the functions and hiogenesis of peroxisomes. This increased knowledge has greatly been stimulated by studies on a genetic disease called Zellwegcr syndrome in which peroxisomer are completely lacking due to a defect in pcroxisomc biogcnesis. Most of thc functions of peroxisomes have to do with lipid metabolism and include: 1. Fatty acid beta-oxidation: peroxisomcs catalyse the baa-oxidative chainshortening of a distinct set of substrates including very-long-chain fatty acids, di-and trihydroxycholestanoic acid and 3. pristanic acid, which is the product of the alfa-oxidation of phytanic acid. 2. Etherphospholipid biosynthesis: synthesis of ether-linked phospholipids including plasmalogens is initiated in pcroxisomes since the first 2 enzymatic reactions catalysed by dihydroxyacetone phosphate acyltransferase (DHAPAT) and alkyl DHAP synthase are strictly peroxisomal. 3. Biosynthcsis of isoprenoids including cholesterol: evidence is increasing that pcroxisomcs play an indispensable role in isoprcnoid formation since enzymes such as medonate kinas...

Distribution and Severity of Neuropathology in β-Mannosidase-Deficient Mice is Strain Dependent

“…Lysosomal storage diseases involve dysfunction of one of the more than 50 enzymes in the lysosome, resulting in the accumulation of the associated uncatabolized substrate (Neufeld 1991;Winchester et al 2000) or toxic intermediates (Suzuki et al 2003). A majority of lysosomal storage diseases affect the CNS and disease presentation can range from severe and consistent to mild and variable depending on the enzyme involved, the severity of the mutation, and the species concerned.…”

“…This autosomal recessive inherited disorder of glycoprotein catabolism is caused by a deficiency of the lysosomal enzyme b-mannosidase (MANBA; EC 3.2.1.25, 609489). MANBA acts exclusively at the last step of oligosaccharide catabolism in glycoprotein degradation and functions to cleave the b-linked mannose sugar found in N-linked oligosaccharides of glycoproteins (Neufeld 1991;Winchester et al 2000). b-Mannosidosis is characterized by the intracellular accumulation of small oligosaccharides (mainly disaccharides and trisaccharides) in selected cell types (Jones and Laine 1981).…”

Lysosome-Related Organelles: A View from Immunity and Pigmentation.

“…During the last two decades many pathological conditions have been identified as lysosomal storage diseases (Winchester et al, 2000). These include genetic deficiencies in specific lysosomal enzymes, in modifications required for the transport of these enzymes to lysosomes, and in proteins required for the biogenesis of lysosomes and/or lysosome-related organelles.…”

Gem-diamine 1-N-iminosugars as versatile glycomimetics: synthesis, biological activity and therapeutic potential

“…An enantioselective synthesis of L-fucose-type gem-diamine 1-Niminosugars from D-ribono-g-lactone was developed that used the Mitsunobu reaction on an aminal in the gem-diamine 1-N-iminopyranose ring formation (74)(75) and a stereospecific reduction of an exo-methylene group to form the correct configuration of L-fucose (75-76) (Scheme 6). 24,25 The synthesis of the pivotal intermediate, Intermediates prepared during the total synthetic route to uronic acid-type gem-diamine 1-N-iminosugars are also available for the synthesis of various kinds of glycose and glycosamine-type gem-diamine 1-N-iminoisugars (Scheme 7).…”