Golgi-derived MTs & Their Functions

This research direction currently includes two projects:

  1. The Golgi as a MTOC
    It is traditionally thought that all microtubules (MTs) in interphase cells are nucleated at the microtubule organizing center (MTOC) associated with the centrosome. We have recently discovered a novel, non-centrosomal microtubule-organizing activity at the Golgi membranes. We identified two important molecular players involved in this process: the MT regulator proteins, CLIP-associated proteins (CLASPs), stabilize growing MTs, while Golgin, GCC185, recruits CLASPs to the Golgi membrane (Dev Cell 2007). A few other important molecules have been detected by other groups; however, we are still far for the  comprehensive understanding of the molecular machinery driving this process.  We are currently screening for essential molecules using in vitro reconstitution techniques. We also use our super-resolution microscopy data to reconstruct the architecture of MT nucleation sites at the Golgi membranes. 
     

  2. Cell-cycle regulation of MT nucleation at the Golgi
    ​We utilize an ice recovery assay to evaluate the potential of the Golgi to nucleate microtubules as a MTOC (Methods Cell Biol 2013), which allows us to analyze this process at specific phase of the cell cycle. Importantly, we found that MT nucleation at the Golgi is tightly regulated depending on the cell cycle stage (Cytoskeleton 2013). However, the signaling pathways and molecular players responsible for this regulation are yet unknown, and are targets of our current research.
     

  3. Functions of the Golgi as a MTOC
    Previously, we found that Golgi-derived MTs are necessary for maintenance of Golgi integrity, vesicular trafficking and cell migration in interphase cells (Nat Cell Biol 2009Mol Biol Cell 2012). Additionally, we discovered that this unique MT sub-population is responsible for Golgi ribbon assembly in telophase: at the end of mitosis the Golgi mini-stacks, which are randomly spread throughout the cytoplasm, are transported along Golgi-derived MTs to reform an integral Golgi complex in each daughter cell (Cytoskeleton 2013). Currently, we are investigating the role of Golgi-derived MTs in Golgi stack redistribution upon entry into prophase. Studying the underlying mechanisms of Golgi positioning in prophase is important as it is likely to be crucial for proper Golgi inheritance by daughter cells.
  • [Project 1] MT nucleation at MTOCs after short ice recovery in an RPE cell. White arrow indicates centrosomal nucleation, yellow arrowheads indicate MTs nucleated at the Golgi. MTs are shown in red, the Golgi is shown in blue, centrosomes are highlighted by GFP-centrin.
  • [Project 2] Image of an RPE cell in interphase with a compact and asymmetrical Golgi complex. MTs are shown in red, the Golgi is shown in cyan, and the centrosomes are labeled with GFP-centrin.