Structure, function and regulation of unidirectional microtubule based motor proteins

The Pfister lab investigates the mechanisms that underlie intracellular transport, in particular the microtubule-based movements driven by the motor protein cytoplasmic dynein.   Defects in dynein function have a role in the development of cancer.  They can result in a failure to properly assemble the mitotic spindle, to properly regulate the spindle checkpoint, or to separate chromosomes which lead to chromosome loss and polyploidy, and the development of tumorogenesis.  Dynein is responsible for the proper localization of the tumor suppressor protein p53.  In addition to its roles in mitosis, dynein is responsible for the positioning of the nucleus during cell migration; the movement of membranous organelles; and the transport or localization of many signal transduction proteins, mRNAs, and viruses.  Dynein is the motor which moves growth factors and their receptors (Trks) from the synapse to the nucleus, an important step in neuronal and synaptic differentiation and maintenance. 

The lab uses two model systems, the mitotic spindle and mammalian axonal transport to understand how dynein is regulated to accomplish its many functions.  The lab has found that there are multiple gene products for 4 of the dynein subunits which are involved in cargo binding (there is only one gene for the motor domain).  These studies have identified specific roles for the some of the subunit isoforms.  One dynein subunit binds the spindle checkpoint protein Bub3 and that led to an investigation of dynein's role in the inactivation of the checkpoint and the transport of checkpoint proteins from the kinetochore to the spindle pole.  The lab has developed cell lines with the stable expression of GFP-dynein.  Thus for the first time the properties of mammalian dynein can be directly studied in vivo.   A collaboration has been established to use purified GFP-dynein to study the properties of single dynein molecules in vitro.   Phosphorylation of several of the subunits in vivo has been characterized, including those of the cargo binding domain and the motor subunit.  In another collaboration, the role of dynein in the transport of Adenovirus to the nucleus is being investigated, work important for understanding basic mechanisms utilized in viral mediated gene therapy.