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Articles by T Sumida
Total Records ( 2 ) for T Sumida
  N Ishimine , Y Usami , S Nogi , T Sumida , Y Kurihara , K Matsuda , K Nakamura , K Yamauchi , N Okumura and M. Tozuka
  Background

In human serum, a portion of homocysteine (Hcy) exists as an N-linked form to the -amino group of protein lysine residues. N-homocysteinylated proteins differ structurally and functionally from native proteins. The present study strives to develop detection and potential semi-quantification methods for N-homocysteinylated apolipoprotein AI (N-Hcy-apoAI) in human serum.

Methods

Serum treated with or without cysteamine was supplied to isoelectric focusing (IEF) followed by an immunoblot using an anti-apoAI antibody. Cysteamine treatment increased the isoelectric point for N-Hcy-apoAI, but not for unmodified apoAI, due to the presence of -SH group(s) derived from Hcy and the absence of a cysteine residue in the apoAI molecule. N-Hcy-apoAI was semi-quantified from the scanned immunoblot pattern via a computer.

Results

After cysteamine treatment, N-Hcy-apoAI in the serum was identified by IEF at the position with a higher pI value compared with intact apoAI. The reproducibility (between assays) of the semi-quantification method was 19.1% CV (coefficient of variation) for an average ratio 5.9% of N-Hcy-apoAI to the whole apoAI in the serum. Approximately 1.0–7.4% of apoAI was N-homocysteinylated in the serum obtained from 27 healthy subjects. Neither the ratio of N-Hcy-apoAI nor its concentration, calculated by total apoAI concentration, indicated correlation with the so-called total (free and S-linked) Hcy concentration.

Conclusions

We directly found that a portion of apoAI in the serum undergoes homocysteinylation in an N-linkage manner, and used this to develop a potential semi-quantification method for N-Hcy-apoAI.

  T Tashiro , E Sekine Kondo , T Shigeura , R Nakagawa , S Inoue , M Omori Miyake , T Chiba , N Hongo , S. i Fujii , K Shimizu , Y Yoshiga , T Sumida , K Mori , H Watarai and M. Taniguchi
 

NKT cells are characterized by their production of both Th1 and Th2 cytokines immediately after stimulation with -galactosylceramide (-GalCer), which is composed of -galactopyranose linked to ceramide (itself composed of sphingosine and fatty-acyl chains); the chain length of the ceramide varies and this affects the ability of -GalCer to stimulate cytokine production. However, the contribution of its galactopyranose sugar moiety remains unclear. We synthesized -carba-GalCer, which has an -linked carba-galactosyl moiety; here, the 5a'-oxygen atom of the D-galactopyranose ring of -GalCer is replaced by a methylene group. The -carba-GalCer was more stable and showed higher affinity to the NKT receptor. It thus enhanced and prolonged production of IL-12 and IFN- compared with -GalCer, resulting in augmented NKT cell-mediated adjuvant effects in vivo. The -carba-GalCer, which has an ether linkage, was more resistant to degradation by liver microsomes than was -GalCer, which has an acetal bond. Modulation of the sugar moiety in glycolipids might therefore provide optimal therapeutic reagents for protective immune responses against tumor or pathogens.

 
 
 
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