Ultrastructural distribution of lectin-binding sites on gastric superficial mucus-secreting epithelial cells

Abstract

Normal human gastric epithelial cells were examined by electron microscopy using each of five biotinylated lectins [Ulex europaeus agglutinin I (UEA-I), peanut agglutinin (PNA), wheat germ agglutinin (WGA), soybean agglutinin (SBA) and Dolichos biflorus agglutinin (DBA)] as a probe. We employed 35 gastric surgical specimens removed from complicated peptic disease. The lectin-binding sites were revealed with streptavidin-colloidal gold complex. All specimens were embedded in Spurr and LR White resins. In superficial foveolar epithelial cells, the lectins used were generally positive in all cell types (mainly UEA-1 and PNA) on the Golgi region and mucus cytoplasmic vacuoles, with many variations among cells in the same case. On the other hand, extracellular mucus was negative for WGA. Labelling with PNA revealed a biphasic pattern (peripheral positivity) on mucous droplets in surface and foveolar cells. The cis side of the Golgi apparatus was labelled with SBA and PNA and rough endoplasmic reticulum with SBA (only five cases). Lectin-binding variability could be related to heterogeneous composition of gastric mucus. Our results with SBA suggest initiation of O-glycosylation at the Golgi apparatus; however a role of the rough endoplasmic reticulum cannot be excluded (N-glycosylation). We propose the following sequence of sugar addition to the carbohydrate side-chains of gastric glycoproteins: (1) GaNAc (Golgi apparatus cis-side), (2) GlcNAc (Golgi apparatus intermediate face), (3) GalNac or Gal, alpha-L-fucose (Golgi apparatus trans-side).

Ontogeny of sulphated glycoconjugate-producing cells in the rat fundic gland

“…Many electron microscopic studies have shown that the Golgi apparatus is the site of sulphation (Lane et al, 1964;Young, 1973;Murata et al, 1979Murata et al, , 1992Parmley et al, 1980;Albedi et al, 1989;Ihida et al, 1991;Rios-Martin et al, 1993). Our results coincided fundamentally with the previous studies in spite of cell and tissue differences.…”

Glycosylation and sorting pathways of lysosomal enzymes in mussel digestive cells

“…Although this is the most conserved form of protein glycosylation in eukaryotes, the modifications of N-linked oligosaccharides in invertebrates often differ greatly from those in vertebrates (Wilson 2002). In contrast, O-glycosylation is diverse and disparate throughout phylogeny (Wilson 2002) and may begin in either the rough ER, in the cis-side of the Golgi apparatus or beyond (Ito et al 1985;Pérez-Villar et al 1991;Ríos-Martín et al 1993;Roth 1984;Roth et al 1994;Röttger et al 1998). Thus, N-glycosylation in insects and nematodes is more akin to that in plants than it is to that in mammals or other vertebrates (Wilson 2002).…”

Concanavalin A-conjugated poly(ethylene glycol)–poly(lactic acid) nanoparticles for intranasal drug delivery to the cervical lymph nodes

“…Binding properties of many lectins with various tissues and cells have been reported in the last few decades (Ríos-Martin et al, 1993;Pusztai et al, 1995;Giannasca et al, 1997;Yi et al, 2001). It has been demonstrated that ConA can diffusely bind to several different types of human airway epithelial cells and endocytosis of ConA occurs within 1 h at 37 C, as evidenced by the obvious fluorescence-ConA appearing at the apical membrane and beneath the apical surface (Yi et al, 2001).…”