Lysosomes lipid

Familial demyelinative/dysmyelinative and axonal neuropathies may also be caused by impaired lysosomal lipid metabolism. Metachromatic leukodystrophy (sulfatide lipidosis) results from mutations of the arylsulfatase A gene, which encodes a lysosomal enzyme required for sulfatide turnover. Myelin is affected in both CNS and PNS, though dysfunction is restricted to the PNS in some patients, and the onset of symptoms can occur at any time between infancy and adulthood. Bone marrow transplantation can slow disease progression and improve nerve conduction velocities [57]. (See in Ch. 41.)... 

Linke, T., Wilkening, G., Sadeghlar,. F, MozcaU, H., Bernardo, K., Schuchman, E., and Sandhoff, K., 2001, Interfacial Regulation of Acid Ceramidase Activity. Stimulation of ceramide degradation by lysosomal lipids and Sphingolipid Activator Proteins. J. Biol. Chem. 276 5760-5768. 

Kolter T, Sandhoff (2005) Principles of lysosomal membrane digestion stimulation of sphingolipid degradation by sphingolipid activator proteins and anionic lysosomal lipids. Annu Rev Cell Dev Biol 21 81-103... 

Unlike lysosomal lipid-storage diseases (see below), very few metabolic diseases are known to be related to mutations of glycosyltransferases in ganglioside synthesis. The one new finding has been from that of Simpson et al. [45], who showed that a nonsense mutation of ST-I (GM3-synthase) is the cause of human autosomal recessive infantile-onset s)mptomatic epilepsy s)mdrome. Because ST-I is a key enz)me in the synthesis of all complex gangliosides, this report clearly indicates that the precise expression of complex gangliosides has critical biological functions in human nervous system development. 

Use of Glycosidase Inhibitors to Treat Lysosomal Lipid Storage Diseases... 

Werth, N., Schuette, C. G., Wilkening, G., Lemm, T., and Sandhoff, K., Degradation of membrane-bound ganglioside GM2 by beta -hexosaminidase A. Stimulation by GM2 activator protein and lysosomal lipids, J Biol Chem 276 (2001) 12685-12690. 

Mucolipin, also known as mucolipin 1 or mucolipidin (encoded by the MCOLN1 gene), is a TRP channel-related membrane protein, most probably residing in intracellular membranes. Is defective in mucolipidosis type IV disease, a developmental neurodegenerative disorder characterized by lysosomal storage disorder and abnormal endocytosis of lipids. The fimction of mucolipin is unknown. 

Transport of proteins and lipids occurs between the organelles of the secretory pathway, i.e. endoplasmic reticulum (ER), Golgi, endosomes, lysosomes and the plasma membrane. 

Vincristine a severe polyneuropathy is a particularly common side effect, but in some patients a painful autophagic myopathy is also present. Abnormal lysosomal complexes are also formed which function as virtually indigestible lipid accumulations. 

Other systems like electroporation have no lipids that might help in membrane sealing or fusion for direct transfer of the nucleic acid across membranes they have to generate transient pores, a process where efficiency is usually directly correlated with membrane destruction and cytotoxicity. Alternatively, like for the majority of polymer-based polyplexes, cellular uptake proceeds by clathrin- or caveolin-dependent and related endocytic pathways [152-156]. The polyplexes end up inside endosomes, and the membrane disruption happens in intracellular vesicles. It is noteworthy that several observed uptake processes may not be functional in delivery of bioactive material. Subsequent intracellular obstacles may render a specific pathway into a dead end [151, 154, 156]. With time, endosomal vesicles become slightly acidic (pH 5-6) and finally fuse with and mature into lysosomes. Therefore, polyplexes have to escape into the cytosol to avoid the nucleic acid-degrading lysosomal environment, and to deliver the therapeutic nucleic acid to the active site. Either the carrier polymer or a conjugated endosomolytic domain has to mediate this process [157], which involves local lipid membrane perturbation. Such a lipid membrane interaction could be a toxic event if occurring at the cell surface or mitochondrial membrane. Thus, polymers that show an endosome-specific membrane activity are favorable. 

Daemen, T., Veninga, A., Dijkstra, J., and Scherphof, G. (1989) Differential effects of liposomeincorpo-ration on liver macrophage activating potencies of rough lipopolysaccharide, lipid A, and muramyl dipeptide Differences in susceptibility to lysosomal enzymes. Immunol. 142, 2469-2474. 

The series of molecular events responsible for the uptake process constitutes the endocytic pathway, which enables cells to internalize macromolecules from the cell exterior, forming an endosome. The endosome is an intermediate organelle that serves as an essential component for many receptor-mediated signaling pathways and as a transport vector for eventual delivery to a specialized organelle known as the lysosome. Once in the lysosomal lumen, digestive enzymes provide essential metabolites from these macromolecules (i.e. free amino acids and lipids) directly to the cytosol for their use. 

Other leukodystrophies are associated with the lysosomal and peroxisomal disorders in which specific lipids or other substances accumulate due to a deficiency in a catabolic enzyme - for example Krabbe s disease, meta-chromatic leukodystrophy (MLD) and adrenoleuko-dystrophy (ALD) [1,2]. (These are discussed in detail in Ch. 40.) Similarly, disorders of amino acid metabolism can lead to hypomyelination - for example phenylketonuria and Canavan s disease (spongy degeneration) [1, 2, 25] (Ch. 40). The composition of myelin in the genetically... 

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