Impaired trafficking of mutants of lysosomal glucocerebrosidase in Gaucher's disease

Gaucher's disease is the most inherited lysosomal storage disorder. Except for a few cases, the broad phenotypic heterogeneity of Gaucher's disease can be neither predicted from defined mutations nor from differences in residual enzyme activity. Here, we analyse the intracellular trafficking of glucocerebrosidase as an underlying mechanism for the expression of the clinical phenotype. Biosynthetic labeling studies combined with immunofluorescence analyses with fibroblasts from patients with the defined mutations N370S, L444P, D409H and G202R unequivocally demonstrate a retarded transport of glucocerebrosidase carrying the mutation N370S and a transport block in the ER of the enzyme with the mutations G202R, L444P and D409H. We asked whether cellular components in the patients' fibroblasts other than glucocerebrosidase are implicated in the onset of the disease. For this, mutant cDNA's corresponding to the phenotypes N370S, G202R and L444P were expressed in the mouse fibroblasts NIH3T3. Essentially similar biochemical and cellular features were revealed as compared to the patients' fibroblasts strongly suggesting that these mutations are exclusively responsible for the characterized phenotypes. Interestingly, the immunoglobulin binding protein (BiP) binds wild type and the mutant N370S but not the G202R and L444P variants suggesting a discriminatory role played by this chaperone associated with the severity of the disease. (c) 2005 Elsevier Ltd. All rights reserve

PP, PYY and NPY : synthesis, storage, release and degradation

Peptides of the NPY family are synthesized as large precursor molecules in the endoplasmatic reticulum (ER), where posttranslational modification takes place, and from where they are translocated to the Golgi apparatus. After several structural and functional adjustments, two types of mature vesicle - large dense core vesicles and synaptic vesicles - serve as a storage depot. Notably, the expression of a gene for a peptide from the NPY family is not sufficient to ensure the production of mature pep tides since several posttranslational steps are specifically involved and these steps themselves are subjected to specific regulatory processes. Similarly, after exocytotic release of NPY-like peptides, their local action depends on their concentration, their different receptor selectivity and the local expression of the different Y-receptors. Another major player in this complex network is found in the action of specific peptidases influencing half-life and receptor selectivity. At least aminopeptidase P, dipeptidylpeptidase IV-like enzymes, specific endopeptidases, like meprin or neprilysin-like enzymes, and post-arginine hydrolyzing endoproteases are cleaving enzymes for NPY-like peptides. Due to a striking change of receptor specificity after N-terminal cleavage of NPY-like peptides, the development of inhibitors for NPY, PYY and PP cleaving peptidases is a complementary approach to the development of Y-receptor agonists or antagonists. In this chapter, we summarize key findings about synthesis, storage, release and localization of NPY family peptides, add recent findings on their degradation by specific enzymes and discuss implications for the interpretation of studies in future research