cDNA structure and expression of calpactin, a peptide involved in Ca2+-dependent cell aggregation in sponges

Abstract

Aggregation of cells of the marine sponge Geodia cydonium is mediated by an aggregation factor (AF) particle of Mr 1.3 X 10(8). It is now reported that the AF particle is associated with calpactin, which was ascribed a role in the cell-adhesion process. In order to identify the sequence similarity to other members of the lipocortin family, the cDNA of sponge calpactin was cloned and found to display an 80% sequence similarity to vertebrate calpactin II but only a 47% similarity to calpactin I. The calpactin gene, which contains the consensus sequence coding for the amino acids G-T-D-E, was expressed in Escherichia coli and subsequently purified to a 37000-Mr polypeptide. Both the p32 and the p37 are provided with approximately two Ca2+ ions/molecule and the property to bind to phospholipids. The dissociation constant (calpactin-Ca2+) was in the absence of phospholipids in the range 500-700 microM-Ca2+ but in their presence about 20-30 microM-Ca2+. On the basis of (i) inhibition studies with antibodies to calelectrin and (ii) competition experiments with soluble phospholipids (both chemically defined as well as total homologous membrane lipids) we conclude that the AF-associated calpactin and plasma-membrane-bound phospholipid(s) are involved in cell-cell aggregation in sponges.

Effect of dietary fat modification on subcutaneous white adipose tissue insulin sensitivity in patients with metabolic syndrome

“…Compared to BSH diet, our study showed that LFHCC n ‐3 diet reduces Anxa2 expression after 12 wk of dietary intervention. Anxa2 is a multifunctional protein that has been shown to play a major role in membrane‐trafficking events, including exocytosis , endocitosis, and cell adhesion . To be more specific, Anxa2 facilitates the transport of cholesterol ester from caveolae to internal membranes and appears to be involved in GLUT4 translocation in a way that has not been fully defined yet .…”

Circular proteoglycans from sponges: first members of the spongican family

“…A sponge 68-kDa protein also bound to CS and HA [122]. The AF from G. cydonium is tightly associated with glycosyltransferases [131,132], lectins [88,133,134], and a series of different glycoproteins [121,135]. Polyclonal antibodies raised against purified AF from G. cydonium inhibited cell aggregation of homologous cells but not of heterologous Tethya lyncurium cells CMLS, Cell.…”

A 35-kDa Protein Is the Basic Unit of the Core from the 2 × 104-kDa Aggregation Factor Responsible for Species-specific Cell Adhesion in the Marine Sponge

“…protein components. The complexity of sponge cell aggregation is suggested by the finding of many proteins associated with the aggregation factor, among them sialyltransferases (Mü ller et al, 1977), protein kinase C (Gramzow et al, 1988b), calpactin (Robitzki et al, 1990), and other bridge proteins that seem to link the factor to the cell membrane receptors (Gramzow et al, 1986;Varner, 1995). Nevertheless, the nature of the main protein component of the aggregation factor core structure has remained elusive.…”