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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.
Max A. Tischfield, Gustav Y. Cederquist, Mohan L. Gupta, Jr., and Elizabeth C. Engle. (2011). Phenotypic spectrum of the tubulin-related disorders and functional implications of disease-causing mutations. Curr Opin Genet Dev 21, 286-94. (PubMed)
Max A. Tischfield, …(44 additional authors)… Alfons Meindl, Mohan L. Gupta, Jr., David Pellman, and Elizabeth C. Engle. (2010). Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance. Cell 140, 74-87. (PubMed)
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)
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