Galectins: regulators of acute and chronic inflammation

TGF-β induces surface LAP expression on murine CD4 T cells independent of Foxp3 induction

Background

It has been reported that human FOXP3⁺ CD4 Tregs express GARP-anchored surface latency-associated peptide (LAP) after activation, based on the use of an anti-human LAP mAb. Murine CD4 Foxp3⁺ Tregs have also been reported to express surface LAP, but these studies have been hampered by the lack of suitable anti-mouse LAP mAbs.

Methodology/Principal Findings

We generated anti-mouse LAP mAbs by immunizing TGF-β^−/− animals with a mouse Tgfb1-transduced P3U1 cell line. Using these antibodies, we demonstrated that murine Foxp3⁺ CD4 Tregs express LAP on their surface. In addition, retroviral transduction of Foxp3 into mouse CD4⁺CD25⁻ T cells induced surface LAP expression. We then examined surface LAP expression after treating CD4⁺CD25⁻ T cells with TGF-β and found that TGF-β induced surface LAP not only on T cells that became Foxp3⁺ but also on T cells that remained Foxp3⁻ after TGF-β treatment. GARP expression correlated with the surface LAP expression, suggesting that surface LAP is GARP-anchored also in murine T cells.

Conclusions/Significance

Unlike human CD4 T cells, surface LAP expression on mouse CD4 T cells is controlled by Foxp3 and TGF-β. Our newly described anti-mouse LAP mAbs will provide a useful tool for the investigation and functional analysis of T cells that express LAP on their surface.

Structure-based evolutionary relationship of glycosyltransferases: a case study of vertebrate β1,4-galactosyltransferase, invertebrate β1,4-N-acetylgalactosaminyltransferase and α-polypeptidyl-N-acetylgalactosaminyltransferase

Cell surface glycans play important cellular functions and are synthesized by glycosyltransferases. Structure and function studies show that the donor sugar specificity of the invertebrate β1,4-N-acetyl-glactosaminyltransferase (β4GalNAc-T) and the vertebrate β1,4-galactosyltransferase I (β4Gal-T1) are related by a single amino acid residue change. Comparison of the catalytic domain crystal structures of the β4Gal-T1 and the α-polypeptidyl-GalNAc-T (αppGalNAc-T) shows that their protein structure and sequences are similar. Therefore, it seems that the invertebrate β4GalNAc-T and the catalytic domain of αppGalNAc-T might have emerged from a common primordial gene. When vertebrates emerged from invertebrates, the amino acid that determines the donor sugar specificity of the invertebrate β4GalNAc-T might have mutated, thus converting the enzyme to a β4Gal-T1 in vertebrates.