Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P20645 (mannose-6-phosphate receptor)
 320 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Methotrexate (MTX) covalently linked to poly(L-lysine) [poly(Lys)] enters cells by endocytosis, is degraded in lysosomes and, upon liberation of small molecular methotrexate, is cytocidal to Chinese hamster cells in culture. This drug conjugate was used to select mutants resistant to MTX-poly(Lys), which were examined for defects in endocytosis. Two mutants resistant to MYX-poly(Lys) and sensitive to free MTX, MPL 3-4 and MPL 2-5, internalized the conjugate in normal fashion, but had a decreased ability to degrade it to small molecular drug. The magnitude of this defect in the two mutants correlated with their level of resistance. In addition, both mutants were cross resistant to diphtheria toxin and modeccin and hypersensitive to ricin. While MPL 3-4 internalized MTX-poly(Lys) and inulin normally, it showed decreased endocytosis via the mannose-6-phosphate receptor and decreased uptake of 125I-alpha-2 macroglobulin. Acidification of subcellular fractions was measured using the partitioning of acridine orange. In MPL 3-4, the ATP-driven acidification of the endosome-containing cell fractions was slightly decreased (80% of controls), while acidification of the heavy lysosome-containing fraction was normal. Complementation analysis using hybrids of MPL 3-4 x MPL 2-5 indicated that the mutations occurred at the same gene, but were expressed with different severity. This genotype is identical to that of the End 2 mutants described by Roff et al. (1986). Thus, surprisingly, mutants with identical genotypes were isolated independently by totally different selection procedures.
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PMID:Methotrexate-poly(lysine) as a selective agent for mutants of Chinese hamster ovary cells defective in endocytosis. 337 97

The crystal structure of human neutrophil cathepsin G, complexed with the peptidyl phosphonate inhibitor Suc-Val-Pro-PheP-(OPh)2, has been determined to a resolution of 1.8 A using Patterson search techniques. The cathepsin G structure shows the polypeptide fold characteristic of trypsin-like serine proteinases and is especially similar to rat mast cell proteinase II. Unique to cathepsin G, however, is the presence of Glu226 (chymotrypsinogen numbering), which is situated at the bottom of the S1 specificity pocket, dividing it into two compartments. For this reason, the benzyl side chain of the inhibitor PheP residue does not fully occupy the pocket but is, instead, located at its entrance. Its positively charged equatorial edge is involved in a favourable electrostatic interaction with the negatively charged carboxylate group of Glu226. Arrangement of this Glu226 carboxylate would also allow accommodation of a Lys side chain in this S1 pocket, in agreement with the recently observed cathepsin G preference for Lys and Phe at P1. The cathepsin G complex with the covalently bound phosphonate inhibitor mimics a tetrahedral substrate intermediate. A comparison of the Arg surface distributions of cathepsin G, leukocyte elastase and rat mast cell protease II shows no simple common recognition pattern for a mannose-6-phosphate receptor-independent targeting mechanism for sorting of these granular proteinases.
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PMID:The 1.8 A crystal structure of human cathepsin G in complex with Suc-Val-Pro-PheP-(OPh)2: a Janus-faced proteinase with two opposite specificities. 889 42

Cortactin is a branched actin regulator and tumor-overexpressed protein that promotes vesicular trafficking at a variety of cellular sites, including endosomes and the trans-Golgi network. To better understand its role in secretory trafficking, we investigated its function in Golgi homeostasis. Here, we report that knockdown (KD) of cortactin leads to a dramatic change in Golgi morphology by light microscopy, dependent on binding the Arp2/3 actin-nucleating complex. Surprisingly, there was little effect of cortactin-KD on anterograde trafficking of the constitutive cargo vesicular stomatitis virus glycoprotein (VSVG), Golgi assembly from endoplasmic reticulum membranes upon Brefeldin A washout, or Golgi ultrastructure. Instead, electron microscopy studies revealed that cortactin-KD cells contained a large number of immature-appearing late endosomal/lysosomal (LE/Lys) hybrid organelles, similar to those found in lysosomal storage diseases. Consistent with a defect in LE/Lys trafficking, cortactin-KD cells also exhibited accumulation of free cholesterol and retention of the retrograde Golgi cargo mannose-6-phosphate receptor in LE. Inhibition of LE maturation by treatment of control cells with Rab7 siRNA or chloroquine led to a compact Golgi morphology similar to that observed in cortactin-KD cells. Furthermore, the Golgi morphology defects of cortactin-KD cells could be rescued by removal of cholesterol-containing lipids from the media, suggesting that buildup of cholesterol-rich membranes in immature LE/Lys induced disturbances in retrograde trafficking. Taken together, these data reveal that LE/Lys maturation and trafficking are highly sensitive to cortactin-regulated branched actin assembly and suggests that cytoskeletal-induced Golgi morphology changes can be a consequence of altered trafficking at late endosomes.
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PMID:Regulation of late endosomal/lysosomal maturation and trafficking by cortactin affects Golgi morphology. 2299 Dec