Properties of SEPT9 Isoforms and the requirement for GTP binding

Members of the evolutionarily conserved septin family of genes are emerging as key components of several cellular processes including membrane trafficking, cytokinesis, and cell-cycle control events. SEPT9 has been shown to have a complex genomic architecture, such that up to 15 different isoforms are possible by the shuffling of five alternate amino termini and three alternate carboxy termini. Genomic and transcriptional alterations of SEPT9 have been associated with neoplasia. The present study has used a Sept9-specific antibody to determine the pattern of isoform expression in a range of tumour cell lines. Western blot analysis indicated considerable variation in the relative amounts and isoform content of Sept9. Immunofluorescence studies showed a range of patterns of cytoplasmic localization ranging from mainly particulate to mainly filamentous. Expression constructs were also generated for each amino terminal isoform to investigate the patterns of localization of individual isoforms and the effects on cells of ectopic expression. The present study shows that the epsilon isoform appears filamentous in this overexpression system while the remaining isoforms are particulate and cytoplasmic. Transient transfection of individual constructs into tumour cell lines results in cell-cycle perturbation with a G2/M arrest and dramatic growth suppression, which was greatest in cell lines with the lowest amounts of endogenous Sept9. Similar phenotypic observations were made with GTP-binding mutants of all five N-terminal variants of Sept9. However, dramatic differences were observed in the kinetics of accumulation of wild-type versus mutant septin protein in transfected cells. In conclusion, the present study shows that the expression patterns of Sept9 protein are very varied in a panel of tumour cell lines and the functional studies are consistent with a model of septin function as a component of a molecular scaffold that contributes to diverse cellular functions. Alterations in the levels of Sept9 protein by overexpression of individual isoforms can clearly perturb cellular behaviour and may thus provide a mechanistic explanation for observations of deranged septin expression in neoplasia. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The Right to Self-Defence in National and International Law: The Role of the Imminence Requirement

This article explores the doctrine of self-defence within the context of the challenges directed at the imminence requirement, from the perspective of both national and international law. The article will attempt to illustrate that the requirement of imminence underlines the political character of the self-defence doctrine wherein private force may only be resorted to in the absence of institutional protection. This study will argue that the imminence rule can not merely be regarded as a "proxy" for establishing necessity; rather, the elements of imminence, necessity, and proportionality are inextricably connected to ensure that defensive force is only resorted to when national or international authorities are not in a position to prevent an illegal aggression, and that the defensive lethal force is not abused.

The Contours of the Right to Self-defence: Is the Requirement of Imminence Merely a Translator for the Concept of Necessity?

The right to self-defence has lately been subjected to intense academic controversy, both at the domestic and international level. The debate is focused on the question of whether or not the requirement of imminence is merely a translator for the notion of necessity. At the domestic level, the debate has mainly been kindled by feminist scholars, who, in the context of the 'battered woman', argue that the requirement of imminence should be discarded from the contours of the self-defence doctrine. The purpose of this article is to prove the necessity of the imminence requirement as a litmus test to detect possible abuses of the self-defence doctrine.