Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The 1I gene is expressed in the prespore cells of culminating Dictyostelium discoideum. The open reading frame of 1I cDNA encodes a protein of 155 amino acids with hydrophobic segments at both its NH(2)- and COOH-termini that are indicative of a glycosyl-phosphatidylinositol (GPI)-anchored protein. A hexaHis-tagged form of 1I expressed in D. discoideum cells appeared on Western blot analysis as a doublet of 27 and 24 kDa, with a minor polypeptide of 22 kDa. None of the polypeptides were released from the cell surface with bacterial phosphatidylinositol-specific phospholipase C, although all three were released upon nitrous acid treatment, indicating the presence of a phospholipase-resistant GPI anchor. Further evidence for the C-terminal sequence of 1I acting as a GPI attachment signal was obtained by replacing the GPI anchor signal sequence of porcine membrane dipeptidase with that from 1I. Two constructs of dipeptidase with the 1I GPI signal sequence were constructed, one of which included an additional six amino acids in the hydrophilic spacer. Both of the resultant constructs were targeted to the surface of COS cells and were GPI-anchored as shown by digestion with phospholipase C, indicating that the Dictyostelium GPI signal sequence is functional in mammalian cells. Site-specific antibodies recognising epitopes either side of the expected GPI anchor attachment site were used to determine the site of GPI anchor attachment in the constructs. These parallel approaches show that the C-terminal signal sequence of 1I can direct the addition of a GPI anchor.
 ...
PMID:The carboxyl terminus of Dictyostelium discoideum protein 1I encodes a functional glycosyl-phosphatidylinositol signal sequence. 1128 75

Disulfide-thiol interchange proteins with hydroquinone (NADH) oxidase activities (designated NOX for plasma membrane-associated NADH oxidases) occur as extrinsic membrane proteins associated with the plasma membrane at the outer cell surface. The cancer-associated NOX protein, designated tNOX, has been cloned. The 34-kDa plasma membrane-associated form of the protein contains no strongly hydrophobic regions and is not transmembrane. No myristoylation or phosphatidylinositol anchor motifs were discovered. Evidence for lack of involvement of a glycosylphosphatidylinositol-linkage was derived from the inability of treatment with a phosphatidylinositol-specific phospholipase C or with nitrous acid at low pH to release the NOX protein from the surface of HeLa cells or from plasma membranes isolated from HeLa cells. Binding of NOX protein to the plasma membrane via amino acid side chain modification or by attachment of fatty acids also is unlikely based on use of specific fatty acid antisera to protein bound fatty acids and as a result of binding to the cancer cell surface of a truncated form of recombinant tNOX. Incubation of cells or plasma membranes with 0.1 M sodium acetate, pH 5, at 37 degrees C for 1 h, was sufficient to release tNOX from the HeLa cell surface. Release was unaffected by protease inhibitors or divalent ions and was not accelerated by addition of cathepsin D. The findings suggest dissociable receptor binding as a possible basis for their plasma membrane association.
 ...
PMID:Surface NADH oxidase of HeLa cells lacks intrinsic membrane binding motifs. 1148 99

Up-regulation of folate receptor (FR) type-beta in acute myelogenous leukemia (AML) by all-trans retinoic acid (ATRA) and its restricted normal tissue distribution makes it a potential target for therapeutic intervention. The FR-beta in peripheral blood granulocytes was unable to bind folate and appeared to have a variant GPI membrane anchor, evident from its insensitivity to phosphatidylinositol-specific phospholipase C but not nitrous acid. Granulocyte FR-beta lacked mutations, and neither deglycosylation nor detergent solubilization restored folate binding. The posttranslational modification causing its nonfunctionality was evidently absent in FR-beta from AML cells from patient marrow, which bound folate. From flow cytometric analysis of 78 AML bone marrow specimens of different subtypes, 68% expressed FR-beta, most of which were also CD34+. In model cell lines that are FR - (KG-1a, L1210, and Chinese hamster ovary [CHO]) or FR + (KG-1, L1210 JF, and recombinant CHO-FR-beta), selective FR-mediated binding and cytotoxicity was obtained using folate-coated liposomes encapsulating fluorescent calcein (f-L-calcein) and doxorubicin (f-L-DOX), respectively, which could be blocked by 1 mM free folic acid. In the FR-beta-expressing KG-1 human AML cells, treatment with ATRA further increased this specificity. In mouse ascites leukemia models generated using L1210JF or KG-1 cells, increased median survival times were obtained with f-L-DOX treatment compared to nontargeted L-DOX. In the KG-1 model, ATRA treatment increased the cure rate with f-L-DOX from 10% to 60%. The above combined data from our 2 laboratories further support the feasibility and potential usefulness of selective ATRA-facilitated liposomal drug delivery in FR-beta + AMLs.
 ...
PMID:Strategy for the treatment of acute myelogenous leukemia based on folate receptor beta-targeted liposomal doxorubicin combined with receptor induction using all-trans retinoic acid. 1209 53

A complex glycoconjugate proteophosphoglycan (PPG) is present on the surface of the pathogenic protozoan parasite Entamoeba histolytica but not in the non-pathogenic Entamoeba dispar. It is thought to be an important molecule involved in pathogenesis. In order to study its biosynthesis, an in vitro cell-free system was developed. The specificity of the system was demonstrated by various criteria including immunoprecipitation by a specific monoclonal antibody. The in vitro synthesized molecule was found to be susceptible to mild acid hydrolysis, digestion by phosphoinositol-specific phospholipase C and nitrous acid deamination, the salient features for a PPG-like molecule. The in vitro product was not synthesized when heat-treated cellular-extract was used in the assay or when the cell extract was prepared from Entamoeba invadens, a species that lacks these glycoconjugates. Analysis of the glycan side chains of the in vitro synthesized product by thin layer chromatography revealed side chains of variable sizes including a fraction greater than six glycan units. The crude membranes used in the cell-free system were further fractionated by sucrose density gradient centrifugation. The fraction containing the PPG synthesizing activity when used in the assay resulted in a 10-fold increase in specific activity. Development of this cell-free system will facilitate further studies on the nature of intracellular organelles and the pathways that are involved in PPG biosynthesis.
 ...
PMID:Biosynthesis of Entamoeba histolytica proteophosphoglycan in vitro. 1255 78


<< Previous 1 2 3 4 5 6 7