Stehbens Group Research Impact
Regulation of Cell-Cell Adhesions by Microtubules
It has long been recognized that cadherins function in close cooperation with the cytoskeleton, particularly with actin. Less appreciated is the capacity for cadherins to also interact functionally and biochemically with microtubules and their associated proteins. Using molecular biology approaches coupled with, immunofluorescence, live-cell microscopy and biosensors, I elucidated the mechanisms in which dynamic microtubules target cadherin-based adhesions to regulate cortical contractility to reinforce junctions (Stehbens et al., Journal of Cell Science 2006). I discovered that microtubules in regulate junctional actomyosin contractility via the GTPase, Rho. This work was the first identification of a non-mitotic role of the centralspindlin complex which is mostly studied in the context of cytokinesis (Ratheesh et al., Nature Cell Biology 2012). The resulting publications together defined a new role for the microtubule cytoskeleton in regulating cell-cell adhesion, reflected by their citation number and quality.
Microtubule-Targeting of Cell-Matrix Adhesions
Migration requires the integration of cell signalling pathways to regulate polarity and dynamic reorganization of the cytoskeleton. This in turn is coordinated with the turnover of specialised tension-sensing membrane domains called focal-adhesions which act as traction points to mediate forward membrane protrusion. While focal adhesions assemble and mature at the cell front in response to tensile stress, little is known about the mechanisms that determine focal adhesion turnover underneath the protruding cell edge. It has been known for years that microtubules were implicated in this process: microtubule targeting of focal adhesions promoted turnover, and de novo microtubule polymerization after wash-out of microtubule-depolymerizing drugs induced focal adhesion disassembly however the molecular mechanism by which microtubules promoted focal adhesion disassembly was known. It was proposed that microtubules target adhesions to release a focal adhesion “disassembly factor”. My study (Stehbens et al., Nature Cell Biology 2014) identified that microtubule-dependent targeting and tethering at focal adhesions was mediated through CLASPs to induce adhesion turnover and establish a local exocytosis pathway of MT1-MMP to degrade matrix during cell migration. Our work pioneered the combined application of quantitative live-cell protein dynamics by both spinning disc confocal and TIRF-M (Total Internal Reflection Microscopy) and the novel super resolution imaging technique, SAIM (Scanning Angle Interference Microscopy). It involved the development of novel analysis methods in combination with custom live-cell imaging set ups. My expertise was recognised by an invited review (Stehbens et al., Journal of Cell Biology 2012) and two requests to collaborate on cell migration projects (Huang et al., Nature Neuroscience 2015 and Kenific et al., Journal of Cell Biology 2016). I designed and performed 95% of the experiments in the first-author papers resulting from this work, and managed the indispensable collaborators including: Matthew Paszek (now UPenn) and Valerie Weaver UCSF, experts on SAIM and cell mechanics, Xi Huang (now at UToronto), Lilly and Yuh Jan (HHMI Investigators) UCSF, neuronal development experts, Jay Debnath Lab UCSF, autophagy expert.
Cell migration and survival in crowded tissue environments
Cells naturally exist in 3D confined environments, where they display unique migration mechanisms not seen in 2D settings. Tumour cells undergo significant deformation in 3D to move through narrow pores in the surrounding matrix or tight spaces within the tumour’s microenvironment. The mechanisms enabling cancer cells to cope with excessive deformations of their body and internal organelles, that are normally incompatible with cell survival, remain unclear. We have uncovered tumour cell specific mechanisms conferring resistance to mechanical stresses (Ju et al., Nature Cell Biology 2024) and mechanisms of cell death in response to sustained mechanical stress (Zhou et al., Nature Communications 2026). Our recent efforts in developing novel 3D ‘mechanically tuneable’ hydrogel models have revealed how cancer cells and fibroblasts respond to changes in the nonlinear elasticity of collagen (Enriquez et al., Science Advances 2025).