Research Summary

Interaction between microtubules and target sites (e.g. kinetochores) is critical for cellular processes such as mitosis, development, and stem cell maintenance. To function in these diverse roles, the dynamic behavior of microtubules must be properly regulated. For example, disruption of microtubule function/organization has been linked to neurodegenerative disease. Alternately, inhibiting microtubule dynamics is among the most effective strategies for cancer therapeutics. Thus, understanding these processes represents a major challenge for cell biology with potential to have significant impact on issues of human health.

Microtubules are regulated by a large and diverse group of proteins. However, due to the transient and dynamic nature of the interactions, the mechanisms involved have been elusive. My lab uses the model organism S. cerevisiae to address fundamental questions about the mechanisms that regulate microtubule function and microtubule interactions within the cell. We utilize various approaches; high-resolution and quantitative microscopy, cell biological approaches in living cells, molecular biology, protein biochemistry, and in-vitro reconstitution assays.

Kinesin motor proteins generally power movement along microtubules. We recently discovered that the important, but poorly understood Kinesin-8 family represents a ‘hybrid’ motor that combines walking and depolymerase activity in the same molecule. Furthermore, we demonstrated that Kinesin-8 operates at the interface between dynamic microtubules and their interaction sites.

Currently, we are working to elucidate the molecular mechanisms and regulation of Kinesin-8 in the context of microtubule interactions. Kinesin-8s are highly conserved and function in critical processes such as spindle positioning, chromosome segregation, and spindle morphogenesis. Thus, Kinesin-8 is an ideal ‘molecular handle’ to leverage against understanding the mechanisms that govern dynamic microtubule interactions.

Figure: Novel mechanisms by which kinesin motor proteins regulate microtubule (MT) function. A) Kinesin-8 uses conventional motility to travel to the MT end where it uses intrinsic depolymerase activity to destabilize the MT. B) Kip2 uses conventional motility to transport the MT stabilizer Bik1 to the MT end.

Selected Publications

Austin, K. M., Gupta, M. L., Jr., Coats, S., Tulpule, A., Mostoslavsky, G., Balazs, A. B., Mulligan, R. C., Daley, G., Pellman, D., and Shimamura, A. (2008). Mitotic spindle destabilization and genomic instability in Shwachman-Diamond syndrome. J Clin Invest., 118:1511-8. (PubMed)

Gupta, M. L., Jr., Carvalho, P., Roof. D. M., and Pellman, D. (2006). Plus end-specific depolymerase activity of Kip3, a kinesin-8 protein, explains its role in positioning the yeast mitotic spindle. Nat Cell Biol. 8:913-23. (PubMed)

Carvalho, P., Gupta, M. L., Jr., Hoyt, M. A., and Pellman, D. (2004). Cell cycle control of kinesin-mediated transport of Bik1 (CLIP-170) regulates microtubule stability and dynein activation. Dev Cell, 6:815-29. (PubMed)

Gupta, M. L., Jr., Bode, C. J., Georg, G. I., and Himes, R. H. (2003). Understanding tubulin-Taxol interactions: mutations that impart Taxol binding to yeast tubulin. Proc Natl Acad Sci USA, 100:6394-7. (PubMed)

Gupta, M. L., Jr., Bode, C. J., Thrower, D. A., Pearson, C. G., Suprenant, K. A., Bloom, K. S., and Himes, R. H. (2002). b-Tubulin C354 mutations that severely decrease microtubule dynamics do not prevent nuclear migration in yeast. Mol Biol Cell. 13:2919-32. (PubMed)

Gupta, M. L., Jr., Bode, C. J., Dougherty, C. A., Marquez, R. T., and Himes, R. H. (2001). Mutagenesis of b-tubulin cysteine residues in Saccharomyces cerevisiae: mutation of cysteine 354 results in cold-stable microtubules. Cell Motil Cytoskeleton, 49:67-77. (PubMed)