Christopher J. Westlake, Ph.D.
Dr. Westlake’s laboratory uses advanced fluorescence and electron microscopy imaging techniques, biochemical approaches and zebrafish models to investigate membrane trafficking processes regulated by the Rab small GTPase family that are important in development and disease. His current work focuses on a Rab11-Rab8 cascade which functions in primary cilium formation and apical membrane formation in polarized cells. His lab is also investigating the role of Rabs in the regulation of ciliary Hedgehog signaling. Defects in primary cilium formation and function are important in ciliopathy, diseases linked to primary cilia dysfunction, and cancer.
The transmission of cellular signals via membrane transport is important for cell homeostasis, growth, motility, and communication. More than 60 Rabs and their associated effectors and modulators regulate membrane vesicle formation, transport, and fusion. Defects in Rab-dependent trafficking are associated with degenerative and neurological disorders and cancer.
Rabs are activated to the GTP-bound state by guanine nucleotide exchange factors (GEF), which catalyze GDP release and reloading of GTP, and inactivated by GTPase-activating proteins (GAPs). In the active state, Rabs associate with effector proteins that are important for regulating membrane transport. Interestingly, Rabs have also been shown to bind GEFs and GAPs as effectors and this appears to be important for regulating downstream membrane trafficking steps. The overall focus of Dr. Westlake's research is on understanding the mechanisms that regulate Rab-dependent membrane transport important in signaling and disease.
One focus of the lab is to understand the molecular mechanism of the Rab11-Rab8 cascade important for primary cilium formation, termed ciliogenesis, and apical membrane formation in polarized cells. Rab8 was previously identified as a regulator of ciliogenesis following the discovery that Rabin8, the Rab8 GEF, associates with the BBSome, a core group of Bardet-Biedl syndrome (BBS) proteins. The primary cilium is present on most cells and defects associated with ciliary signaling, including the Sonic hedgehog pathway, have been linked to BBS and a growing list of genetic diseases and certain cancers.
Our prior work suggests that ciliogenesis initiation is preceded by the signaling-dependent binding of Rabin8 to Rab11. Rabin8 is transported via Rab11-recycling endosomes to the centrosome where Rab8 is activated to assemble the primary cilium membrane. We have developed advanced microscopy techniques to monitor in real-time the assembly of the primary cilium - a process completed in approximately 100 minutes.
Cell biology, proteomics, biochemistry and genetics approaches are being used to indentify and characterize associated factors in this pathway. As an example of this approach, mass spectrometry analysis of purified LAP (localization and affinity purification)-tagged Rabin8 was used to identify interactions with the TRAPPII complex, found to be required for Rabin8 centrosomal targeting and ciliogenesis. We are also investigating the roles of these and other membrane transport pathways in the sorting of receptors to the cilia and in the transmission of ciliary signals within the cell.
Selected Key Publications
- Nat. Cell Biol. 17: 228-40, 2015. [ Journal Article ]
- Proc. Natl. Acad. Sci. U.S.A. 104: 1236-41, 2007. [ Journal Article ]
Primary cilia membrane assembly is initiated by Rab11 and transport protein particle II (TRAPPII) complex-dependent trafficking of Rabin8 to the centrosome.Proc. Natl. Acad. Sci. U.S.A. 108: 2759-64, 2011. [ Journal Article ]
A role for the Golgi matrix protein giantin in ciliogenesis through control of the localization of dynein-2.J. Cell. Sci. 126: 5189-97, 2013. [ Journal Article ]
- Mol. Biol. Cell. 25: 1629-40, 2014. [ Journal Article ]
In 2004, Dr. Westlake obtained his Ph.D. in Biochemistry under the supervision of Dr. Roger Deeley at Queen's University in Canada. While there, he investigated the structure/function and trafficking of multidrug resistance proteins (MRP) that are important in resistance to chemotherapeutics. He then joined Dr. Richard Scheller at Genentech as a postdoctoral fellow investigating membrane trafficking regulation by the Rab small GTPase family. In 2011, Dr. Westlake joined the Laboratory of Cell and Developmental Signaling at the Center for Cancer Research where he studies membrane trafficking pathways important in ciliopathy, diseases linked to primary cilia dysfunction, and cancer.
|Adrian Cuenca Ph.D.||Postdoctoral Fellow (CRTA)|
|Christine Kettenhofen Ph.D.||Postdoctoral Fellow (CRTA)|
|Quanlong Lu Ph.D.||Postdoctoral Fellow (Visiting)|
|Elizabeth Semler||Postbaccalaureate Fellow (CRTA)|
|Jimmy Stauffer Ph.D.||Research Biologist|
|Huijie Zhao Ph.D.||Postdoctoral Fellow (Visiting)|