Abstract 1219: Tubulin binding to mitochondrial VDAC: A new regulator of oxidative metabolism and apoptosis? A new role for tubulin

Abstract Tubulin binding to the outer mitochondrial membrane (OMM) was first reported many years ago but the function was unknown; we showed recently that dimeric tubulin binds to VDAC, the major metabolite channel in the OMM, and that this results in closing the channel to ATP-ADP exchange, with a consequent drop in oxidative phosphorylation. This could act as a regulator of normal oxidative metabolism, but excess tubulin binding could also lead to changes in the inner membrane potential, and possibly lead to mitochondrial swelling and triggering of apoptosis. To evaluate the plausibility of this mechanism for either regulation of normal metabolism or induction of apoptosis, the concentrations of tubulin and VDAC in the cell need to be known, as a huge discrepancy in either direction could make the mechanism unlikely. We have used semiquantitative Western blots to measure the concentrations of tubulin and VDAC in total cell extracts from a number of cancer cell lines. As expected, we found tubulin to be an abundant protein (∼0.5 % of total protein), but we also found VDAC to be more abundant than perhaps commonly thought (∼0.2 % of total protein). Thus we conclude that tubulin regulation of VDAC permeability is a plausible mechanism. Further experiments are underway to test this mechanism and its role in induction of apoptosis by chemotherapy agents, especially microtubule-directed ones. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1219.</jats:p

Abstract 2790: Localization of the binding site for Peloruside A and Laulimalide on beta-tubulin by physical and biological means

Abstract Peloruside A (Pel) and laulimalide (Laul) are microtubule-stabilizing natural products that were discovered recently compared to more established agents such as the taxanes and the epothilones. The activities of Pel and Laul are synergistic with taxanes or epothilones but not with each other, indicating separate binding sites and distinct mechanisms for Pel and Laul compared to taxanes and epothilones. Hence the location and nature of the Pel / Laul binding site is of interest. We have identified this site by a physical method (mass spec H-D footprinting) and a biological one: isolating Pel-resistant mutants of human ovarian carcinoma cells (A2780 (1A9)). Four Pel-resistant lines were obtained with single-base mutations in class I β-tubulin which resulted in the following substitutions: R306H, Y340S, N337D, and A296S in various combinations. The mutations localize to the peptides identified by the mass spec method, and center on a cleft in which modeling indicates that the Pel and Laul side chains dock. The site is accessible from the outside of the microtubule and does not overlap the Taxol site on β-tubulin. The Pel resistant lines are cross resistant to Laul, but not to any other microtubule stabilizing drug, and show no cross-sensitivity to microtubule destabilizing drugs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2790. doi:1538-7445.AM2012-2790</jats:p

Total Synthesis and Biological Evaluation of Tubulysin U, Tubulysin V, and Their Analogues

A stereoselective total synthesis of the cytotoxic natural products tubulysin U, tubulysin V, and its unnatural epimer epi-tubulysin V, is reported. Simplified analogues containing N,N-dimethyl-d-alanine as a replacement for the N-terminal N-Me-pipecolinic acid residue of the tubulysins are also disclosed. Biological evaluation of these natural products and analogues provided key information with regard to structural and stereochemical requirements for antiproliferative activity and tubulin polymerization inhibition

Leukotriene B ₄ antagonism ameliorates experimental lymphedema

Lymphedema is a common debilitating condition with very limited treatment options, and leukotriene B 4 may be a key pathogenic molecule and therapeutic target. </jats:p