Syntaxin is required for cell division.

We recently identified a single family member homologue of syntaxin in the sea urchin. Syntaxin is present throughout development, and in rapidly dividing cleavage stage embryos it is present on numerous vesicles at the cell cortex. We hypothesized that syntaxin mediates essential membrane fusion events during early embryogenesis, reasoning that the vesicles and/or their contents are important for development. Here we show that functional inactivation of syntaxin with either Botulinum neurotoxin C1, which specifically proteolyzes syntaxin, or antibodies against syntaxin results in an inhibition of cell division. These observations suggest that syntaxin is essential for membrane fusion events critical for cell division.

LL-E19020 alpha and beta, animal growth promoting antibiotics: taxonomy, fermentation and biological activity.

Antibacterial antibiotics LL-E19020 alpha and beta were isolated from the fermentation broth of an actinomycete strain. Based on cultural and physiological characteristics, culture LL-E19020 was identified as a new subspecies of Streptomyces lydicus. The LL-E19020 alpha and beta antibiotics were found to possess a very narrow antibacterial spectrum against human pathogens. In studies in chickens, LL-E19020 alpha demonstrated excellent growth promoting activity.

Syntaxin, VAMP, and Rab3 are selectively expressed during sea urchin embryogenesis.

SNARE and rab protein family members were originally identified in terminally differentiated cell types. These proteins are phylogenetically conserved and while compelling evidence demonstrates their involvement in the secretory pathway, their exact function is debated. We recently identified SNARE protein family members in the sea urchin egg and provided evidence that rab3 functions in the exocytosis of cortical granules. Here we tested the hypothesis that these same proteins might also be present throughout embryogenesis to mediate membrane fusion events. We provide evidence that the sea urchin possesses a low complexity of gene family members of syntaxin, VAMP, and rab3 and that these proteins are not only present during development, but are enriched in regions of the embryo with active secretory roles. We found accumulation of each family member in the apical and basal aspects of cleaving blastomeres, indicative of bidirectional secretion into the extraembryonic environment and blastocoel. Elevated levels of syntaxin, VAMP, and rab3 were also found in the mesodermally derived pigment cells that invade and move within the ectoderm. These cells likely rely on SNARE and rab proteins to enable mobility by mediating the secretion of enzymes that break adhesion to neighboring cells and the extracellular matrix. In addition, these secretory proteins are enriched in the gut following gastrulation. Thus, we conclude that VAMP, syntaxin, and rab3 mediate a variety of secretory events that is important for development.

A rab3 homolog in sea urchin functions in cell division.

Rabs are monomeric GTP binding proteins belonging to the ras superfamily that function throughout the secretory pathway. Members of the rab3 family function in the final steps of the secretory pathway, vesicle fusion with the plasma membrane. In contrast to mammalian systems with several rab3 isoforms (rab3A-D), a single family member homologue of rab3 is present in the rapidly dividing cleavage stage sea urchin embryo that localizes to numerous vesicles enriched at the cell cortex. We hypothesized that whereas the contents of these rab3-positive vesicles may contribute to the embryonic extracellular matrix, the membrane and its constituent proteins may be important for other aspects of cell division. We tested the function of rab3 in cell division by the microinjection of either antibodies or competing effector domain peptides to interfere with its function. We found that perturbing rab3 function results in cessation of cell division, whereas cells injected with either heat-inactivated antibodies or control scrambled peptides develop as normal. Moreover, neither endocytosis nor general membrane topology are affected by rab3 perturbation. Thus, we conclude that rab3-associated vesicles and/or their contents are critical for cell division.