Identification and isolation of the primary aggregation factor from the cell membrane of the sponge Geodia cydonium

Abstract

The primary aggregation factor (pAF) of sponge cells is a glycoprotein that is firmly associated with the cell membrane. Polyspecific antibodies (anti-GM) prepared from sera raised against membranes of cells from the siliceous sponge Geodia cydonium were found to inhibit initial aggregation of homologous cells. The inhibition of aggregation, caused by anti-GM was neutralized by pAF. The pAF had been successfully solubilized and enriched by affinity chromatography, gel filtration and density gradient centrifugation, if checked by polyacrylamide gel electrophoresis in the presence of urea. The Mr of the native pAF was approximately 40 000 as estimated by gel filtration; under denaturing conditions three protein species (Mr: 16 500, 15 500 and 13 500) were identified in the pAF preparation. The pAF was precipitable by Ca++ and did not cross-react with antisera against homologous purified secondary aggregation factor and lectin. It is mainly composed of protein (48.0%) and carbohydrate (50.2%). The isolated pAF restored the aggregation potency not only of factor-depleted Geodia cells but also of cells from other Demospongiae. However, the pAF displayed no aggregation enhancing effect on urea-treated cells from species belonging to the Calcispongiae or Hexactinellida. We hypothesize that in contrast to the secondary aggregation, the initial aggregation of Geodia cells is mediated by the one-component system, the bivalent and bifunctional pAF.

Circular proteoglycans from sponges: first members of the spongican family

“…Each of the 20 arms is attached to one of the 20 globular structures in the ring in a 1:1 stoichiometry, with an estimated molecular mass for the whole molecule of 2 ¥10 7 Da [76,77]. The structure of the AF from G. cydonium has also been investigated, and found to be equivalent to that of M. prolifera in the dimensions and sunburst-like appearance [99], core proteins sequence [123], glycosylation [124], and role in specific sponge cell adhesion [99]. AFs extracted from Halichondria bowerbankii, Terpios zeteki, H. occulata, and Halichondria panicea have a very similar size and structure, but with a linear backbone [103,122] that strongly resembles the classical image of hyalectans ( fig.…”

Porifera Lectins: Diversity, Physiological Roles and Biotechnological Potential

“…The most studied lectin in this physiological context was the G. cydonium galectin. GCG was involved in a complex system linking sponge cells via an aggregation factor (AF), which was formed by selectin-related molecules (86 kDa) and aggregation factor proteins (36 kDa) [ 90 , 91 , 92 ]. This complex was linked to an aggregation receptor (scavenger receptor cysteine-rich/short consensus repeat), localized on the membrane of the sponge cells [ 93 ].…”

Inhibitory effect of nonviable preparations from human immunodeficiency virus 1 on inositol phospholipid metabolism

“…Pokeweed mitogen was radioiodinated following the chloramine T procedure, using Na1251 [16]. Lymphocytes were centrifuged (1000 x g , 5 min, 25°C) and resuspended in RPMI medium without serum at a concentration of 5 x lo6 cells/ml.…”