Identification of discrete classes of endosome-derived small vesicles as a major cellular pool for recycling membrane proteins.

Vesicles carrying recycling plasma membrane proteins from early endosomes have not yet been characterized. Using Chinese hamster ovary cells transfected with the facilitative glucose transporter, GLUT4, we identified two classes of discrete, yet similarly sized, small vesicles that are derived from early endosomes. We refer to these postendosomal vesicles as endocytic small vesicles or ESVs. One class of ESVs contains a sizable fraction of the pool of the transferrin receptor, and the other contains 40% of the total cellular pool of GLUT4 and is enriched in the insulin-responsive aminopeptidase (IRAP). The ESVs contain cellubrevin and Rab4 but are lacking other early endosomal markers, such as EEA1 or syntaxin13. The ATP-, temperature-, and cytosol-dependent formation of ESVs has been reconstituted in vitro from endosomal membranes. Guanosine 5'-[gamma-thio]triphosphate and neomycin, but not brefeldin A, inhibit budding of the ESVs in vitro. A monoclonal antibody recognizing the GLUT4 cytoplasmic tail perturbs the in vitro targeting of GLUT4 to the ESVs without interfering with the incorporation of IRAP or TfR. We suggest that cytosolic proteins mediate the incorporation of recycling membrane proteins into discrete populations of ESVs that serve as carrier vesicles to store and then transport the cargo from early endosomes, either directly or indirectly, to the cell surface.

Effect of carbonyl cyanide m-chlorophenylhydrazone (CCCP) on the dimerization of lipoprotein lipase.

Lipoprotein lipase (LPL), an enzyme playing the central role in triglyceride metabolism, is a glycoprotein and a homodimer of identical subunits. Dimerization and proper processing of oligosaccharide chains are important maturation steps in post-translational regulation of enzyme activity. Indirect evidences suggest that dimerization of LPL occurs in endoplasmic reticulum (ER) or Golgi. In this study, we investigated the dimerization status of LPL in 3T3-L1 adipocytes, using sucrose density gradient ultracentrifugation and carbonyl cyanide m-chlorophenylhydrazone (CCCP), an inhibitor of ER-Golgi protein transport. In the presence of CCCP, no increase of cellular LPL activity was detected during 2 b of recovery period after the depletion of LPL, with heparin and cycloheximide. Only endoglycosidase H (endo H)-sensitive subunits were found in CCCP-treated cells after endo H digestion, suggesting that inactive LPL was retained in ER. In the presence of castanospermine, an inhibitor of ER glucosidase I, LPL subunits of both control and CCCP-treated cells had same molecular weight, indicating that complete oligosaccharides were transferred to LPL subunits in the presence of CCCP. In sucrose density gradient ultracentrifugation, all the LPL protein synthesized in the presence of CCCP was found at the dimeric fractions as in control cells. Most of LPL protein in control cells showed high affinity for heparin, and there was no difference between the control and CCCP-treated cells. These results suggest that dimerization and acquisition of high affinity for heparin of LPL can occur in ER of CCCP-treated cells without acquisition of catalytic activity.

Glycosylation, dimerization, and heparin affinity of lipoprotein lipase in 3T3-L1 adipocytes.

The relationship between glycosylation, dimerization, and heparin affinity of lipoprotein lipase (LPL) was studied in 3T3-L1 adipocytes. Three forms of LPL subunits were found in normal cells; totally endo H-resistant (57 kDa), partially sensitive (54 kDa), and totally sensitive (51 kDa) forms. LPL in normal cells was active, dimeric, and showed high affinity for heparin. LPL in cells treated with tunicamycin, preventing the transfer of N-linked oligosaccharide chain, was unglycosylated (51 kDa) and inactive. LPL proteins were found as an aggregate, and had low affinity for heparin. After treatment with castanospermine, an inhibitor of ER glucosidase I, 80% of LPL activity was inhibited. Most of LPL proteins were totally endo H-sensitive, present as an aggregate, and had low affinity for heparin. LPL in cells treated with deoxymannojirimycin, an inhibitor of Golgi mannosidase I, was active, dimeric, and had high affinity for heparin as in normal cells. But LPL subunits were all endo H-sensitive. These results suggest that core glycosylation and subsequent removal of glucose residue is required, but processing after Golgi mannosidase I is not necessary for dimerization and acquisition of high heparin affinity of LPL.

A variant of ornithine aminotransferase from mouse small intestine.

The ornithine aminotransferase (OAT) activity of mouse was found to be highest in the small intestine. The mitochondrial OAT from mouse small intestine was purified to homogeneity by the procedures including heart treatment, ammonium sulfate fractionation, octyl-Sepharose chromatography, and Sephadex G-150 gel filtration. Comparing to the amino acid sequence of mouse hepatic OAT, six N-terminal amino acid residues have been deleted in intestinal OAT. However, the subsequent sequence was identical with that of hepatic OAT. The molecular weights of both intestinal and hepatic OAT were estimated as 46 kDa by SDS-gel electrophoresis and as 92 kDa by gel filtration, indicating that both native OATs are dimeric. Biochemical properties of intestinal OAT, such as molecular weight, pH optimum and K(m) values for L-ornithine and alpha-ketoglutarate, were similar to those of hepatic OAT. However, intestinal OAT was more labile than hepatic OAT to tryptic digestion.

Evaluation of antioxidative activity of extracts from a brown seaweed, Sargassum siliquastrum.

Antioxidative activities of the extracts from Sargassum siliquastrum were determined using the inhibition of red blood cell (RBC) hemolysis induced by 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) radicals, suppression of lipid peroxidation using rat brain homogenate, and scavenging activity of superoxide radicals. The dichloromethane fraction isolated from the methanol crude extract by differential solvent extractions exhibited the strongest antioxidant activity in both RBC hemolysis and lipid peroxidation assays. This fraction was further fractionated into four subfractions F1-F4 by silica gel column chromatography. F1 was found to be most effective in protecting RBC against AAPH radicals and in inhibiting lipid peroxidation. On the basis of thin-layer chromatography and UV and IR spectra analyses, all subfractions contained phenolic compounds. However, there was no correlation between the above antioxidant potency and total phenolic compounds estimated by using the Folin-Ciocalteau method.

Allogeneic hematopoietic cell transplantation for myelodysplastic syndrome: prognostic significance of pre-transplant IPSS score and comorbidity.

We analyzed the clinical significance of pre-transplant International Prognostic Scoring System (IPSS) score and comorbidity in 68 patients who underwent allogeneic hematopoietic cell transplantation (HCT) for myelodysplastic syndrome (MDS) (n=48) or acute myeloid leukemia evolved from MDS (n=20) between December 1995 and January 2008 in a single institute. During a median follow-up period of 41.0 months (range, 3.2-132.0 months), 27 patients died, and 7 relapsed. The 5-year probabilities of overall survival (OS) and event-free survival (EFS) were 60.0 and 57.4%, respectively, and the 5-year cumulative incidences of non-relapse mortality (CINRM) and relapse were 32.7 and 9.9%, respectively. OS, EFS, and CINRM were significantly different according to pre-transplant IPSS score and presence of pre-transplant comorbidity, which were independent risk factors along with Karnofsky performance score in multivariate analyses. In conclusion, pre-transplant IPSS score and comorbidity may stratify the risk of post transplant outcomes in MDS.

Reevaluation of the National Institutes of Health criteria for classification and scoring of chronic GVHD.

We used the National Institutes of Health (NIH) criteria for the diagnosis, classification and scoring of chronic GVHD (cGVHD) to reevaluate patients with cGVHD originally diagnosed using classic criteria. We retrieved data from 236 patients diagnosed with cGVHD on the basis of classic criteria. Excluding 20 'liver-alone' patients, we re-categorized 216 patients in keeping with the NIH criteria. Twenty patients were reclassified as having acute GVHD and 196 patients as having cGVHD (170 'classic chronic' (Cl-Ch) and 26 'overlap chronic' (Ov-Ch)). The 5-year GVHD-specific survival (GSS) was significantly different between the two cGVHD subtypes, specifically 87.3% for Cl-Ch vs 70.2% for Ov-Ch (P=0.006). The NIH severity criteria were effective in expecting 5-year GSS rates at both the onset (93.5, 81.3 and 79.7% (P=0.047)) and peak intensity of the disease (100, 89.7 and 78.7% (P=0.004) for the mild, moderate and severe grade, respectively). Multivariate analysis showed that NIH severity criteria were independently significant prognostic factors for GSS (mild vs moderate, HR 4.35, P=0.036; mild vs severe, HR 5.25, P=0.020). Our results support the role of the NIH criteria in classifying cGVHD and in assessing the severity of the disease to predict patient prognosis of cGVHD.