China
Africa
Explore chapters and articles related to this topic
Sly disease/β-glucuronidase deficiency/mucopolysaccharidosis VII
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
β-Glucuronidase was a key enzyme in the development of current understandings of lysosomal enzyme processing. It was in studies of this enzyme that the mannose-6-phosphate recognition marker was first identified [6]. Full-length cDNAs from the human and rodent genes have been cloned, sequenced, and expressed; they encode polypeptides of 651 and 648 amino acids, respectively [7, 8]. The gene is 21 kb in length and contains 12 exons [9]. It is located at chromosome 7 q21-22 [10]. The mutation has been defined in the initial patient [11] and a small number of others [11–13].
Pathology of the Liver: Functional and Structural Alterations of Hepatocyte Organelles Induced by Cell Injury
Published in Robert G. Meeks, Steadman D. Harrison, Richard J. Bull, Hepatotoxicology, 2020
Louis Marzella, Benjamin F. Trump
The biogenesis of lysosomal enzymes follows the RER-SER-Golgi route that is taken by lipids and proteins destined for export to the extracellular space (Marzella and Glaumann, 1983). A “signal” amino acid sequence on the nascent lysosomal enzyme determines the insertion of the oligopeptide chain into the lumen of the ER. Proteolytic removal of the signal sequence and addition of carbohydrate chains to the nascent oligopeptide also occur in the ER (Nishimura et al., 1988). In the Golgi apparatus, processing of the carbohydrate chains of the lysosomal enzymes occurs. The lysosomal enzymes bind to mannose-6-phosphate receptors in the Golgi region and are transported within vesicles to the lysosomes either directly or, as has recently been proposed, via an endosomal compartment. Transport of lysosomal enzymes that is independent of mannose-6-phosphate receptors also occurs. The various enzymes are transported through the ER-Golgi route at different rates possibly because of specific interactions with other membrane proteins that may regulate rates of transport (Cardelli et al., 1986). Apparently physiologic secretion of lysosomal enzymes from hepatocytes has also been described (Nishimura et al., 1988).
Post-Translational Regulation of C-Reactive Protein Secretion
Published in Andrzej Mackiewicz, Irving Kushner, Heinz Baumann, Acute Phase Proteins, 2020
Stephen S. Macintyre, Patricia A. Kalonick
Nevertheless, we did observe weak inhibition by phosphocholine of the interaction between CRP and rough microsomes. One possible explanation for this finding would be that phosphocholine is a constituent of the rough microsomal binding site for CRP (i.e., the 60-kDa protein could be a phospholipoprotein) and the greater apparent affinity of this site for CRP is due to additional protein structure. Such a phenomenon would be analogous to the observation that the affinity of the cation-dependent mannose-6-phosphate receptor for mannose-6-phosphate expressed in lysosomal enzymes is substantially greater than that for free mannose-6-phosphate.61 Alternatively, phosphocholine could be exerting an allosteric effect, since it is known that the interaction of phosphocholine with CRP results in a conformational change in CRP.63 Thus, phosphocholine added to the assay could bind to free CRP and result in a conformational change which lessens the ability of CRP to bind, via another site, to the rough microsomal membrane. Indeed, the observed Ki of about 3 µM (Figure 5D) for phosphocholine in the binding assay is in agreement with what would be expected for the interaction between CRP and free phosphocholine, having a Kd of 5 µM.61 The lack of inhibition of microsomal binding by human CRP suggests that the effect of phosphocholine on the binding of rabbit CRP to rough microsomes is due to an allosteric effect of phosphocholine on the CRP molecule, although it remains possible that phosphocholine is a constituent of the binding site and that additional protein structure increases the affinity for rabbit CRP, but also sterically interferes with the interaction of human CRP with the phosphocholine moiety of the microsomal binding site.
M6P-modified solid lipid nanoparticles loaded with matrine for the treatment of fibrotic liver
Published in Drug Delivery, 2023
Xiaochuan Tan, Yumei Hao, Nai Ma, Yige Yang, Wenzhen Jin, Ya Meng, Chuchu Zhou, Wensheng Zheng, Yujia Zhang
The M6P-HSA was synthesized and characterized as reported previously (Beljaars et al., 1999) (Figure 1C). Firstly, p-nitrophenyl-a-D-mannopyranoside was phosphorylated by phosphorus oxychloride, and p-nitrophenyl-6phospho-a-D-mannopyranoside (MW 381) was obtained. Subsequently, the nitro group was reduced with 10% palladium on activated carbon under 1.5 atm of hydrogen for 4h to obtain the p-aminophenyl-6-phospho-a-D-mannopyranoside (pap-M6P, MW 350). Then the p-aminophenyl-6-phospho-a-D-mannopyranoside was coupled to HSA by diazo bond formation to get M6P-HSA. The resulting M6P-HSA was purified and analyzed by Sephadex G-50 gel chromatography to determine its molecular weight. The 6-phosphate-p-nitrophenyl-α-D-mannose, p-aminophenyl-α-D-mannose, 6-phosphate-1-(4-isothiocyanatephenol) -α-D-mannose and M6P-HSA were purified and verified by mass spectrometry. Unmodified HSA protein was isolated using Superdex 75.
An update on gene therapy for lysosomal storage disorders
Published in Expert Opinion on Biological Therapy, 2019
Murtaza S. Nagree, Simone Scalia, William M. McKillop, Jeffrey A. Medin
Many lysosomal enzymes are transported into the lysosome by the mannose-6-phosphate receptor (M6PR) pathway [2]. Terminal mannose residues phosphorylated in the cis-Golgi interact with M6PR. Protein-M6PR complexes then traffic to the lysosome via vesicular transport [3]. Lysosomal enzymes can be secreted into the extracellular space, though it is unclear if this is a consequence of mis-sorting or an active process. M6PR is expressed on the surface of many cell types; this can serve to scavenge extracellular enzyme back to the lysosome [4]. Incidentally, the secretion of some lysosomal enzymes is dramatically increased when overexpressed, and a significant proportion of secreted enzyme is appropriately modified for uptake and transport to lysosomes [5]. Standard-of-care for some LSDs is treatment with enzyme therapy (ET; commonly referred to as Enzyme Replacement Therapy; ERT). In ET, enzyme purified ex vivo is infused and subsequently taken up by M6PR-expressing cells [6].
Enzyme replacement combinational therapy: effective treatments for mucopolysaccharidoses
Published in Expert Opinion on Biological Therapy, 2021
Azam Safary, Hakimeh Moghaddas-Sani, Mostafa Akbarzadeh-Khiavi, Alireza Khabbazzi, Mohammad A. Rafi, Yadollah Omidi
Today, the enzymes for ERT are produced by recombinant DNA technologies using mammalian cells. Accordingly, Chinese hamster ovary (CHO) cells are usually considered as the best expression system to produce recombinant enzymes because they offer several advantages such as appropriate post-translational modifications (PTMs), extracellular secretion of the enzymes, and proper protein folding which are comparable to the native enzymes. Although the CHO cell line can produce recombinant proteins in high yield with complex post-translational modifications (PTMs) similar to the human cells, they insert non-human PTMs such as galactose-α1 (α-gal), 3-galactose, and N-glycolylneuraminic acid (NGNA). Such undesired PTMs may induce human immune responses against the proteins produced by CHO cells. Besides, these cells are not able to produce some human PTMs, in large part due to the lack of α-2-6 sialyltransferase α-1-3/4 fucosyltransferases. Undoubtedly, the human cell lines can produce proteins with the best PTMs pattern. Such potential can be considered as one of the most important advantages of these cells in comparison with the other mammalian expression system. A potential disadvantage of the animal cell lines may be the possibility of specific viral contamination, which can be managed with viral inactivation and clearance processes [65]. Binding and cellular uptake of the recombinant enzymes are mediated by mannose 6-phosphate (M6P). Recombinant phosphorylated/non-phosphorylated enzymes rapidly clear from the blood circulation through the mannose 6-phosphate receptors (M6PRs) or mannose receptors, which are located on the cell membrane, and then traffic to the lysosomes. Therefore, the M6P content and sialylation of the recombinant enzyme must be optimized for maximal lysosomal delivery [66]. The following contexts briefly introduce the recombinant enzymes used for the treatment of MPS or are in the end stage of clinical trials.