Oral Presentation Australasian Society for Dermatological Research Annual Scientific Meeting 2017

Understanding how dynamic microtubules regulate cell migration by targeted exocytosis at cell-matrix adhesions (#11)

Samantha Stehbens 1 2 , Matthew Paszek 2 3 , Hayley Pemble 2 , Andreas Ettinger 2 , Sarah Gierke 2 4 , Torsten Wittmann 2
  1. University of Queensland, Brisbane, QLD, Australia
  2. Cell and Tissue Biology, University of California San Francisco, San Francisco, CA, USA
  3. Cornell University, Ithaca, NY, USA
  4. Genentech, Inc, South San Francisco, CA, USA

Collective cell migration is a fundamental cellular process essential for development and homeostatic processes. It is also unfortunately a mechanism exploited by tumour cells during metastatic invasion. The molecular mechanisms governing collective cell migration are poorly understood. Turnover of integrin-based focal adhesions (FAs) is essential for coordinated cell movement. In migrating keratinocytes, FAs assemble near the leading edge, maturing as a result of contractile forces, and subsequently disassemble underneath the advancing cell body in a process known as turnover. Microtubules have been implicated in FA turnover although the molecular mechanisms are incompletely understood. Here we identify the microtubule associated proteins, CLASPs, as critical molecules linking microtubules to FA turnover. Using high-resolution microscopy, we found that FA turnover and CLASP dynamics are spatio-temporally correlated. Depletion of CLASP by lentivirus-mediated shRNA in HaCaT cells resulted in larger FAs which turned over more slowly. Using Scanning Angle Interference Microscopy, a novel axial super-resolution technique (Paszek et al., Nature Methods 2012), we that CLASPs anchor microtubules at FAs. We found that CLASP-mediated microtubule-tethering at FAs establishes a Rab6a-positive vesicle transport pathway for delivery, docking and localized fusion of MT1-MMP exocytic vesicles near FAs, thereby promoting FA-associated, localized degradation of the extracellular matrix. We propose that CLASPs function as key molecules coupling microtubule organization, vesicle transport and cell interactions with the extracellular matrix, establishing a local secretion pathway that facilitates FA turnover by severing cell–matrix connections. FA-associated exocytosis may be more broadly important for ECM remodelling and play central roles in normal and pathological tissue dynamics. In addition, other exocytic cargo is likely transported along these FA-associated microtubule tracks, and it will be important to determine to what extent this pathway is involved in more physiological three-dimensional cell migration systems in which directed vesicle trafficking to the protruding cell tip depends on microtubule functions.

  1. Nat Cell Biol. 201416(6):561-73. doi: 10.1038/ncb2975. CLASPs link focal-adhesion-associated microtubule capture to localized exocytosis and adhesion site turnover. Stehbens SJ, Paszek M, Pemble H, Ettinger A, Gierke S, Wittmann T.
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