Identification, localization, and functional implications of an abundant nematode annexin.

Abstract

Abstract. Cultures of the nematode C. elegans were examined for the presence of calcium-dependent, phospholipid-binding proteins of the annexin class. A single protein of apparent mass on SDS-polyacrylamide gels of 32 kD was isolated from soluble extracts of nematode cultures on the basis of its ability to bind to phospholipids in a calcium-dependent manner. After verification of the protein as an annexin by peptide sequencing, an antiserum to the protein was prepared and used to isolate a corresponding cDNA from an expression library in phage k gtll. The encoded protein, herein referred to as the nex-1 annexin, has a mass of 35 kD and is 36-42% identical in sequence to 10 known mammalian annexins. Several unique modifications were found in the portions of the sequence corresponding to calcium-binding sites. Possible phosphorylation sites in the NH2-terminal domain of the nematode annexin correspond to those of mammalian annexins. The gene for this annexin (nex-1) was physically mapped to chromosome III in the vicinity of the dpy-17 genetic marker. Two other annexin genes (nex-2 and nex-3)were also identified in chromosome III sequences reported by the nematode genomic sequencing project (Sulston, J., Z. Du, K. Thomas, R. Wilson, L. Hillier, R. Staden, N. Halloran, P. Green, J. Thierry-Mieg, L. Qiu, et al. 1992. Nature (Lond.). 356:37-41). The nex-1 annexin was localized in the nematode by immunofluorescence and by electron microscopy using immunogold labeling. The protein is associated with membrane systems of the secretory gland cells of the pharynx, with sites of cuticle formation in the grinder in the pharynx, with yolk granules in oocytes, with the uterine wall and vulva, and with membrane systems in the spermathecal valve. The presence of the annexin in association with the membranes of the spermathecal valve suggests a novel function of the protein in the folding and unfolding of these membranes as eggs pass through the valve. The localizations also indicate roles for the annexin corresponding to those proposed in mammalian systems in membrane trafficking, collagen deposition, and extracellular matrix formation.

Lipocortin V May Function as a Signaling Protein for Vascular Endothelial Growth Factor Receptor-2/Flk-1

“…Lipocortins (annexins) are a family of at least 18 structurally related cytoplasmic proteins in mammals, which exhibit Ca 2ϩ -dependent binding to phospholipids (35,36). These proteins are widely distributed in eukaryotic cells and are characterized by a similar structure, with four or eight repeats of a 70-amino acid conserved core, and differ by a variable N-terminal domain.…”

Parasite annexins – New molecules with potential for drug and vaccine development

“…While nex-1 and nex-3 are expressed continuously in the developmental stages of C. elegans, the expression of nex-2 and nex-4 was reported to be only temporal [32]. The highest expressed member of this protein family, nex-1, is present in many structures in the worm [33]. Ultrastructural studies of nex-1 showed it to be localized to the spermathecal valve, a structure that represents the final gate for the egg on its passage from the ovary to the spermathecal chamber.…”

Identification and Functional Analysis of Salmon Annexin 1 Induced by a Virus Infection in a Fish Cell Line

“…Annexins have been found in many species of eukaryotes, including Xenopus (22), Drosophila melanogaster (23), Dictyostelium (11), Caenorhabditis elegans (8), Neurospora (1), Giardia (15), zebrafish (13), and all of the plant types (9) so far examined. Structurally annexins can be characterized as having a core of either four or eight conserved domains, each containing about 70 amino acids.…”