Cell and Chemical Biology of Microtubules

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Project Summary/Abstract: We will investigate the cell and chemical biology of microtubules in order to answer fundamental questions of cell organization and improve treatment of human diseases. Microtubules are dynamic, linear polymers of the protein tubulin. They physically organize the cytoplasm of most human cells, and serve as transport tracks for moving cellular components. They are particularly important during cell division, when they build mitotic spindles which separate chromosomes, and in neurons, where they provide transport tracks for supplying distant synapses with new building blocks. We will probe cell division mechanism using frog eggs as a model system. Our work may help treat infertility and understand mistakes in cell division that give rise to birth defects. We k now most of the proteins required for cell division, but we do not know how they work together to build spindles or position cleavage furrows. We will use a new tool, quantitative mass spectrometry, to simultaneously measure hundreds of proteins in mitotic spindles in frog egg extracts, and how they compete for binding sites on microtubules. We will also combine microscopy, biochemistry and mathematical modeling to learn how the spindle communicates with the cell surface to position cleavage furrows. In neurons, we will investigate how tubulin is transported down axons, and test a new hypothesis in which stathmin proteins serve as transport adapters. This work will address a fundamental question in neuronal cell biology, and may help treat motor neuron disease (ALS). Drugs that target microtubules and are used as medicines can provide important insights into microtubule biology in adult human tissues. These include paclitaxel, which is used to treat breast and lung cancer, and colchicine, which is used to treat gout and other inflammatory diseases. We understand the molecular actions of these drugs on microtubules in detail, but not how they act in the human body to treat disease. We have developed new hypothesis for the therapeutic action of both drug classes, and will test these in cell culture and rodent models. This work could lead to new uses of old drugs, for example we suspect low doses of colchicine might be useful to prevent heart attacks and slow the progression of lung cancer. It could also lead to replacement drugs that are more active and less toxic.