Assembling complex cytoskeletal architectures from simple building blocks.

For a living cell to function properly, its cellular processes must be strictly controlled not only in time but also in space. We are interested in how intracellular spatial organization on the micron-length scale is achieved by nanometer-sized proteins.  

We investigate this problem in the context of specialized microtubule-based machineries that are required for two cellular processes: (i) cell division and (ii) intercellular signaling through the cilium.  Increasingly sophisticated genomic and proteomic analyses have now provided us with a near-complete ‘parts-list’ of the proteins involved in assembling the microtubule-based structures required for these processes. However, the molecular mechanisms underlying the proper formation and activity of even the minimal functional units of these structures still remain poorly understood. We aim to bridge this knowledge gap by ‘building’ or reconstituting microtubule-based architectures from the individual components.

We use a diverse set of experimental tools in our endeavor. X-ray crystallography and single-molecule visualization techniques are used for interrogating the reactions occurring on the angstrom and nanometer-length scale. These methods are complemented with fluorescence microscopy-based in vitro reconstitution assays that provide information on the micron-length scale, and integrated with cell-biological analyses.

Selected Publications:

He, M., Subramanian, R., Bangs, F., Omelchenko, T., Liem, K.F., Kapoor, T.M., and Anderson, K.V.  (2014) The kinesin-4 protein Kif7 regulates mammalian Hedgehog signalling by organizing the cilium tip compartment. Nat. Cell Biol. 16(7):663-72.

Subramanian, R., and Kapoor, T.M. (2013)  Slipping past the spindle assembly checkpoint. Nat. Cell Biol. 15(11):1261-3.

Subramanian, R., Ti, S.C., Tan, L., Darst, S.A., and Kapoor, T.M. (2013)  Marking and measuring single microtubules by PRC1 and kinesin-4. Cell 154(2):377-90.

Subramanian, R., and Kapoor, T.M.  (2012) Building complexity: insights into self-organized assembly of microtubule-based architectures. Dev. Cell 23(5):874-85.