Investigations on the lectin-producing cells in the sponge Axinella polypoides (Schmidt)

Abstract

The localization of two carohydrate binding proteins, so-called lectins, was studied in the sponge tissue of Axinella polypoides by light and immunofluorescence microscopy. They do not occur at the cellular surface of any cell type, but they are stored in vesicles of the "spherulous cells". After short formaldehyde fixation spherulous cells can be isolated and they release the active lectins upon lysis in distilled water. Electron microscopical studies of spherulous cells show that they contain almost nothing else but a small nucleus and vesicles of different size and number. Small vesicles are full of an electron dense material, whereas the content of large vesicles has a fluffy and fibrillar structure. Spherulous cells are large and tightly packed in the outer layer of the ectosome and in the meshwork of the spongin fibres of the central axis. The are small and scattered in the inner layer of the ectosome, and they are found throughout the choanosome. The function of the lectins is not clearly defined, and different alternatives such as participation in glycoprotein synthesis, immunological defense, or carbohydrate transport are possible.

Mechanical adaptability of a sponge extracellular matrix: evidence for cellular control of mesohyl stiffness inChondrosia reniformisNardo

“…These include cells with membrane-bounded cytoplasmic vesicles that in other sponges release their contents into the extracellular compartment. Amongst the materials thus released are lectins (Bretting and Königsmann, 1979), a class of small molecules that may have a structural role in mammalian collagenous structures (Tidball, 1994;Ozeki et al, 1995). Lectins are stored in the vesicles of I. C. Wilkie and others spherulous cells (Bretting and Königsmann, 1979;Bretting et al, 1983), which in C. reniformis are particularly abundant in the ectosome (Bonasoro et al, 2001).…”

New light on the cell location of avarol within the sponge Dysidea avara (Dendroceratida)

“…Young et al 1980) and of their metabolic pathways (e. g. Cimino and Sodano 1993). In sponges, studies of bioactivity at the cellular level or of particular bioactive metabolites have rarely been accomplished (Bretting and Königsmann 1979;Thompson et al 1983;Müller et al 1986;Garson et al 1992;Uriz et al 1995).…”

Cellular Defense Systems of the Porifera

“…These particular lectins are not present as cell-membrane-bound molecules and are therefore unlikely to participate in normal cell-to-cell contact and recognition. Instead, they are found in secretory vacuoles within spherulous cells of the mesohyl (Bretting and Konigsmann, 1979). In an unnamed species of Axinella, MacLennan (1974) described a similar galactose-specific component that had no effect when assayed for agglutination with conspecific sponge cells.…”