The core fucosylation (␣1,6-fucosylation) of glycoproteins is widely distributed in mammalian tissues, and is altered under pathological conditions. To investigate physiological functions of the core fucose, we generated ␣1,6-fucosyltransferase (Fut8)-null mice and found that disruption of Fut8 induces severe growth retardation and death during postnatal development. Histopathological analysis revealed that Fut8 ؊/؊ mice showed emphysema-like changes in the lung, verified by a physiological compliance analysis. Biochemical studies indicated that lungs from Fut8 ؊/؊ mice exhibit a marked overexpression of matrix metalloproteinases (MMPs), such as MMP-12 and MMP-13, highly associated with lung-destructive phenotypes, and a down-regulation of extracellular matrix (ECM) proteins such as elastin, as well as retarded alveolar epithelia cell differentiation. These changes should be consistent with a deficiency in TGF-␤1 signaling, a pleiotropic factor that controls ECM homeostasis by down-regulating MMP expression and inducing ECM protein components. In fact, Fut8 ؊/؊ mice have a marked dysregulation of TGF-␤1 receptor activation and signaling, as assessed by TGF-␤1 binding assays and Smad2 phosphorylation analysis. We also show that these TGF-␤1 receptor defects found in Fut8 ؊/؊ cells can be rescued by reintroducing Fut8 into Fut8 ؊/؊ cells. Furthermore, exogenous TGF-␤1 potentially rescued emphysema-like phenotype and concomitantly reduced MMP expression in Fut8 ؊/؊ lung. We propose that the lack of core fucosylation of TGF-␤1 receptors is crucial for a developmental and progressive͞ destructive emphysema, suggesting that perturbation of this function could underlie certain cases of human emphysema.fucosylation ͉ glycobiology ͉ matrix metalloproteinase

Chronic renal disease (CRD) is generally thought to be incurable, except through renal transplantation, and the number of patients with CRD is on the increase. Glomerulosclerosis and tubulointerstitial fibrosis represent the morphological equivalent of end-stage CRD. In this study, we demonstrated the preventive effect of hepatocyte growth factor (HGF) on the progression of renal dysfunction and fibrosis, using a spontaneous mouse model for CRD (ICGN strain). The mice progressively developed glomerular sclerotic injury, tubular atrophy, and renal dysfunction until they were 17 wk of age. When recombinant HGF was injected into these mice during a 4-wk-period (from weeks 14-17 after birth), DNA synthesis of tubular epithelial cells was found to be 4.4-fold higher than in mice without HGF injection, thereby suggesting tubular parenchymal expansion promoted by HGF. Notably, HGF suppressed the expression of transforming growth factor-beta and of platelet-derived growth factor as well as myofibroblast formation in the affected kidney. Consequently, the onset of tubulointerstitial fibrosis was almost completely inhibited by HGF, while HGF attenuated the progression of glomerulosclerosis, both leading to preventing manifestation of renal dysfunction. From our results, supplement therapy with HGF may be taken into consideration as a novel option for prevention and treatment of CRD.

The ␣1,6-fucosyl residue (core fucose) of glycoproteins is widely distributed in mammalian tissues and is altered under pathological conditions. A probe that specifically detects core fucose is important for understanding the role of this oligosaccharide structure. Aleuria aurantia lectin (AAL) and Lens culimaris agglutinin-A (LCA) have been often used as carbohydrate probes for core fucose in glycoproteins. Here we show, by using surface plasmon resonance (SPR) analysis, that Aspergillus oryzae L-fucose-specific lectin (AOL) has strongest preference for the ␣1,6-fucosylated chain among ␣1,2-, ␣1,3-, ␣1,4-, and ␣1,6-fucosylated pyridylaminated (PA)-sugar chains. These results suggest that AOL is a novel probe for detecting core fucose in glycoproteins on the surface of animal cells. A comparison of the carbohydrate-binding specificity of AOL, AAL, and LCA by SPR showed that the irreversible binding of AOL to the ␣1,2-fucosylated PA-sugar chain (H antigen) relative to the ␣1,6-fucosylated chain was weaker than that of AAL, and that the interactions of AOL and AAL with ␣1,6-fucosylated glycopeptide (FGP), which is considered more similar to in vivo glycoproteins than PA-sugar chains, were similar to their interactions with the ␣1,6-fucosylated PA-sugar chain. Furthermore, positive staining of AOL, but not AAL, was completely abolished in the cultured embryo fibroblast (MEF) cells obtained from ␣1,6-fucosyltransferase (Fut8) knock-out mice, as assessed by cytological staining. Taken together, these results suggest that AOL is more suitable for detecting core fucose than AAL or LCA.

Fucosylated ␣-fetoprotein (AFP) is a highly specific tumor marker for hepatocellular carcinoma (HCC). However, the molecular mechanism by which serum level of fucosylated AFP increases in patients with HCC remains largely unknown. Here, we report that the fucosylation of glycoproteins could be a possible signal for secretion into bile ducts in the liver. We compared oligosaccharide structures on glycoproteins in human bile with those in serum by several types of lectin blot analyses. Enhanced binding of biliary glycoproteins to lectins that recognize a fucose residue was observed over a wide range of molecular weights compared with serum glycoproteins. A structural analysis of oligosaccharides by two-dimensional mapping high performance liquid chromatography and matrix-assisted laser desorption ionization time-of flight mass spectrometry confirmed the increases in the fucosylation of biliary glycoproteins. Purification followed by structural analysis on ␣1-antitrypsin, ␣1-acid glycoprotein and haptoglobin, which are synthesized in the liver, showed higher fucosylation in bile than in serum. To find direct evidence for fucosylation and sorting signal into bile ducts, we used ␣1-6 fucosyltransferase (Fut8)-deficient mice because fucosylation of glycoproteins produced in mouse liver was mainly an ␣1-6 linkage. Interestingly, the levels of ␣1-antitrypsin and ␣1-acid glycoprotein were quite low in bile of Fut8-deficient mice as compared with wild-type mice. An immunohistochemical study showed dramatic changes in the localization of these glycoproteins in the liver of Fut8-deficient mice. Taken together, these results suggest that fucosylation is a possible signal for the secretion of glycoproteins into bile ducts in the liver. A disruption in this system might involve an increase in fucosylated AFP in the serum of patients with HCC.

Not only an increase in TGF-beta 1 level, but also a decrease in local HGF expression may be responsible for the manifestation of renal fibrosis, particularly tubular destruction.