Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.23.5 (cathepsin D)
 4,130 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated the effect of a glycosylphosphatidylinositol anchor on the distribution of the soluble lysosomal enzyme cathepsin D. Only 10% of the chimeric protein (CD-GPI) could be detected on the plasma membrane after transfection in CHO cells. Similarly to endogenous cathepsin D, intracellular CD-GPI was detected in vesicular structures, suggesting that CD-GPI is targeted to lysosomes. CD-GPI is present as three forms with M(r) 55, 50 and 37 kD which could correspond to the precursor, intermediate and mature forms of cathepsin D, respectively. CD-GPI was shown to be GPI anchored by differential extractability with Triton X-114 before and after phosphatidylinositol phospholipase C hydrolysis. Intracellular CD-GPI is mainly substituted with oligosaccharides containing uncovered mannose 6-phosphate residues whereas these residues are covered in the cell surface precursor form of CD-GPI. Ammonium chloride treatment reduces the lysosomal delivery of CD-GPI and increases the cell surface expression of its precursor form.
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PMID:Localization and processing of glycosylphosphatidylinositol anchored cathepsin D. 759 25

Leishmania major promastigotes, when grown in the presence of tunicamycin (TM), produced a plasma membrane-bound, proteolytically active gp63 with a lower molecular weight than the native glycoprotein. However, this lower molecular weight form of gp63 continued to be recognized by concanavalin A (Con A), suggesting that inhibition of N-linked glycosylation was not complete. Metabolic labeling of gp63, using [35S]methionine, demonstrated that in the range of 5-10 micrograms ml-1 TM, only the lower molecular weight form was synthesized, suggesting that inhibition was complete and that lectin binding was likely due to the GPI anchored sugars. Removal of the oligosaccharides from L. major and L. mexicana amazonensis promastigotes using endoglycosidase F, caused the gp63 molecular weight to decrease to the same value observed in the presence of TM, once again without affecting the proteolytic activity. However, this deglycosylated enzyme continued to bind Con A until subsequently treated with periodate. The latter oxidation reaction resulted in complete loss of Con A binding without inhibiting the protease activity or the substrate specificity of gp63. Further investigations revealed that both glycosylated and deglycosylated gp63 were resistant to proteolytic digestion by either autolysis or cathepsin D. These findings indicate that the N-linked oligosaccharides of gp63 are not essential for folding, transport, maintenance of enzyme activity or resistance to proteolysis.
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PMID:An investigation into the significance of the N-linked oligosaccharides of Leishmania gp63. 818 21

According to the protein-only hypothesis of prion propagation, prions are composed principally of PrP(Sc), an abnormal conformational isoform of the prion protein, which, like its normal cellular precursor (PrP(C)), has a GPI (glycosylphosphatidylinositol) anchor at the C-terminus. To date, elucidating the role of this anchor on the infectivity of prion preparations has not been possible because of the resistance of PrP(Sc) to the activity of PI-PLC (phosphoinositide-specific phospholipase C), an enzyme which removes the GPI moiety from PrP(C). Removal of the GPI anchor from PrP(Sc) requires denaturation before treatment with PI-PLC, a process that also abolishes infectivity. To circumvent this problem, we have removed the GPI anchor from PrP(Sc) in RML (Rocky Mountain Laboratory)-prion-infected murine brain homogenate using the aspartic endoprotease cathepsin D. This enzyme eliminates a short sequence at the C-terminal end of PrP to which the GPI anchor is attached. We found that this modification has no effect (i) on an in vitro amplification model of PrP(Sc), (ii) on the prion titre as determined by a highly sensitive N2a-cell based bioassay, or (iii) in a mouse bioassay. These results show that the GPI anchor has little or no role in either the propagation of PrP(Sc) or on prion infectivity.
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PMID:Removal of the glycosylphosphatidylinositol anchor from PrP(Sc) by cathepsin D does not reduce prion infectivity. 1644 Dec 39

Until now there is no molecular model of starch digestion and absorption of the resulting glucose molecules along the larval midgut of Musca domestica. For addressing to this, we used RNA-seq analyses from seven sections of the midgut and carcass to evaluate the expression level of the genes coding for amylases, maltases and sugar transporters (SP). An amylase related protein (Amyrel) and two amylase sequences, one soluble and one with a predicted GPI-anchor, were identified. Three highly expressed maltase genes were correlated with biochemically characterized maltases: one soluble, other glycocalyx-associated, and another membrane-bound. SPs were checked as being apical or basal by proteomics of microvillar preparations and those up-regulated by starch were identified by real time PCR. From the 9 SP sequences with high expression in midgut, two are putative sugar sensors (MdSP4 and MdSP5), one is probably a trehalose transporter (MdSP8), whereas MdSP1-3, MdSP6, and MdSP9 are supposed to transport glucose into cells, and MdSP7 from cells to hemolymph. MdSP1, MdSP7, and MdSP9 are up-regulated by starch. Based on the data, starch is at first digested by amylase and maltases at anterior midgut, with the resulting glucose units absorbed at middle midgut. At this region, low pH, lysozyme, and cathepsin D open the ingested bacteria and fungi cells, freeing sugars and glycogen. This and the remaining dietary starch are digested by amylase and maltases at the end of middle midgut and up to the middle part of the posterior midgut, with resulting sugars being absorbed along the posterior midgut.
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PMID:Molecular machinery of starch digestion and glucose absorption along the midgut of Musca domestica. 2980 61