Antibody-dependent cellular cytotoxicity-mediated serotherapy against murine neuroblastoma

Summary The in vitro and in vivo activity has been investigated of antisera prepared against a murine (C-1300) neuroblastoma line (MNB) capable of differentiation. An antibody-dependent cellular cytotoxicity (ADCC) reaction was employed using rat spleen cells (RSC). ADCC activity in vitro (using ⁵¹Cr-release) was shown, but a maximum of only 50% of the immunologically releasable ⁵¹Cr was achieved. Nevertheless, in vivo (syngeneic mouse-tumor flank assay) significant delays were obtained in tumor onset and lethality. Under ideal circumstances, i.e., coating of tumor cells prior to inoculation and high RSC effector cell ratios, a significant number of animals could be cured of substantial tumor burdens (10⁶ cells). While close proximity of the site of injection of effector cells was required (ectopic injections of RSC were ineffective), the anti-MNB ADCC was shown to be quite active in vivo without external precoating of the cells with antisera. RCS obtained from BCG-treated rats were more numerous and slightly more effective. RSC obtained from -radiated animals retained normal activity. With appropriate antisera this approach could be useful under selected clinical circumstances.     

The evolutionarily conserved domain of Beclin 1 is required for Vps34 binding, autophagy and tumor suppressor function

Atg6/Beclin 1 is an evolutionarily conserved protein family that has been shown to function in vacuolar protein sorting (VPS) in yeast; in autophagy in yeast, Drosophila, Dictyostelium, C.elegans, and mammals; and in tumor suppression in mice. Atg6/Beclin 1 is thought to function as a VPS and autophagy protein as part of a complex with Class III phosphatidylinositol 3'-kinase (PI3K)/Vps34. However, nothing is known about which domains of Atg6/Beclin 1 are required for its functional activity and binding to Vps34. We hypothesized that the most highly conserved region of human Beclin 1 spanning from amino acids 244-337 is essential for Vps34 binding, autophagy, and tumor suppressor function. To investigate this hypothesis, we evaluated the effects of wild-type and mutant beclin 1 gene transfer in autophagy-deficient MCF7 human breast carcinoma cells. We found that, unlike wild-type Beclin 1, a Beclin 1 mutant lacking aa 244-337 (Beclin 1DeltaECD), is unable to enhance starvation-induced autophagy in low Beclin 1-expressing MCF7 human breast carcinoma cells. In contrast to wild-type Beclin 1, mutant Beclin 1DeltaECD is unable to immunoprecipitate Vps34, has no Beclin 1-associated Vps34 kinase activity, and lacks tumor suppressor function in an MCF7 scid mouse xenograft tumor model. The maturation of cathepsin D, which requires intact Vps34-dependent VPS function, is comparable in autophagy-deficient low-Beclin 1 expressing MCF7 cells, autophagy-deficient MCF7 cells transfected with Beclin 1DeltaECD, and autophagy-competent MCF7 cells transfected with wild-type Beclin 1. These findings identify an evolutionarily conserved domain of Beclin 1 that is essential for Vps34 interaction, autophagy function, and tumor suppressor function. Furthermore, they suggest a connection between Beclin 1-associated Class III PI3K/Vps34-dependent autophagy, but not VPS, function and the mechanism of Beclin 1 tumor suppressor action in human breast cancer cells.     

hVps34 is a nutrient-regulated lipid kinase required for activation of p70 S6 kinase

Mammalian cells respond to nutrient deprivation by inhibiting energy consuming processes, such as proliferation and protein synthesis, and by stimulating catabolic processes, such as autophagy. p70 S6 kinase (S6K1) plays a central role during nutritional regulation of translation. S6K1 is activated by growth factors such as insulin, and by mammalian target of rapamycin (mTOR), which is itself regulated by amino acids. The Class IA phosphatidylinositol (PI) 3-kinase plays a well recognized role in the regulation of S6K1. We now present evidence that the Class III PI 3-kinase, hVps34, also regulates S6K1, and is a critical component of the nutrient sensing apparatus. Overexpression of hVps34 or the associated hVps15 kinase activates S6K1, and insulin stimulation of S6K1 is blocked by microinjection of inhibitory anti-hVps34 antibodies, overexpression of a FYVE domain construct that sequesters the hVps34 product PI3P, or small interfering RNA-mediated knock-down of hVps34. hVps34 is not part of the insulin input to S6K1, as it is not stimulated by insulin, and inhibition of hVps34 has no effect on phosphorylation of Akt or TSC2 in insulin-stimulated cells. However, hVps34 is inhibited by amino acid or glucose starvation, suggesting that it lies on the nutrient-regulated pathway to S6K1. Consistent with this, hVps34 is also inhibited by activation of the AMP-activated kinase, which inhibits mTOR/S6K1 in glucose-starved cells. hVps34 appears to lie upstream of mTOR, as small interfering RNA knock-down of hVps34 inhibits the phosphorylation of another mTOR substrate, eIF4E-binding protein-1 (4EBP1). Our data suggest that hVps34 is a nutrient-regulated lipid kinase that integrates amino acid and glucose inputs to mTOR and S6K1.     

Extracellular gelsolin binds lipoteichoic acid and modulates cellular response to proinflammatory bacterial wall components

The various functions of gelsolin in extracellular compartments are not yet clearly defined but include actin scavenging and antiinflammatory effects. Gelsolin was recently reported to bind endotoxin (LPS) from various Gram-negative bacteria with high affinity. In this study we investigate whether gelsolin also interacts with bacterial wall molecules of Gram-positive bacteria such as lipoteichoic acid (LTA) and whether gelsolin's interaction with bacterial lipids from Gram-negative or Gram-positive bacteria affects their cellular inflammatory responses. A peptide based on the PPI binding site of gelsolin (160-169) binds purified LTA at the same molecular ratio that it binds phosphatidylinositol 4,5-bisphosphate. The OD of recombinant human plasma gelsolin was found to decrease following the addition of purified LTA, and the binding of gelsolin to LTA inhibits F-actin depolymerization by gelsolin. Simultaneously, the ability of LTA to activate translocation of NF-kappaB, E-selectin expression, and adhesion of neutrophils to LTA-treated human aortic endothelial cells was compromised by gelsolin. Gelsolin was able to partially inhibit LPS- or LTA-induced release of IL-8 from human neutrophils but was unable to prevent Gram-positive Bacillus subtilis or Gram-negative Pseudomonas aeruginosa growth and had no effect on the antibacterial activity of the cathelicidin-derived antibacterial peptide LL37. These data suggest that extracellular gelsolin is involved in the host immune recognition of LTA or LPS following release of these molecules from the bacterial outer membrane during cell division or attack by drugs and immune components.     

93 Progress in characterizing the symbiodinium sp. in soritid foraminifera

Our research seeks to clarify the phylogeny of the Caulerpales through analyses of rbcL (large subunit of ribulose 1,5 biphosphate carboxylase/oxygenase) gene sequences. In a review of caulerpalean taxonomy, Hillis-Colinvaux (1984) recognized two suborders (Bryopsidineae and Halimedineae) on the basis of anatomical, physiological, and habitat characteristics. The Bryopsidineae (including the genera Bryopsis, Derbesia , and Codium ) have cosmopolitan distributions, non-holocarpic reproduction, and homoplasty, while the Halimedineae (including Caulerpa, Halimeda, and Udotea) have tropical to subtropical distributions, holocarpic reproduction, and heteroplasty. Previous phylogenetic analyses based on 18S rRNA sequence data supported the hypothesis of two monophyletic suborders within the Caulerpales (Zechman et al 1990). However, cladistic analyses of morphological characters (Vroom 1998) suggested that only the Halimedineae was monophyletic. Preliminary maximum likelihood and Bayesian analyses suggest the Halimedineae and Bryopsidineae form separate monophyletic groups, with robust support (bootstrap and posterior probabilities) for the former and moderate to poor support for the latter. The families of the Halimedineae (Caulerpaceae, Udoteaceae) form monophyletic sister groups with robust support. The freshwater family Dichotomosiphonaceae was inferred to be basal to the marine Halimedineae clade. The families within the Bryopsidineae (Derbesiaceae, Bryopsidaceae, Codiaceae) each form distinct monophyletic groups. The Codiaceae forms a basal monophyletic group to the sister clade of Bryopsidaceae and Derbeseaceae. This research was partially supported from a NSF grant (DEB-0128977 to FWZ).