Supplement request for TIRF microscope for studies on the role of Microtubule regulators in HIV-1 infection

Microtubules (MTs) form complex intracellular networks that not only provide mechanical stability for cell structure and motility, but also form the tracks along which molecular motors traffic cargos to specific sub-cellular sites. While most MTs have a relatively short half-life, a subset of post-translationally modified MTs are highly stable and function in various biological processes. However, their role and regulation during viral infection remains poorly understood. Our screens for host factors that determine cellular susceptibility to infection, in collaboration with Gundersen (Project 1), Walsh (Project 3) and Goff (Project 4) identified a number of novel regulators of stable MT formation, highlighting the potential role of this stable subset of MTs as specialized tracks for viral trafficking. Our collaborative effort with Gundersen to explore this more directly resulted in the identification of the kinesin, Kif4 as an EB1-interacting regulator of MT stability and HIV-1 infection. Kif4 is also bound by Gag, a retroviral structural polyprotein that has been suggested to promote MT stabilization. Combined with our preliminary data showing that HIV-1 infection promotes stable MT formation and incoming viral cores colocalize with stable MT subsets, this suggests that Kif4 and EB1 form a specialized MT tip-binding complex specifically targeted by HIV-1. In this proposal we will map the domains in Kif4 and EB1 that mediate their effects on MT stability and trafficking of HIV-1 during both early stage (inward-directed) movement of viral cores and late stage (outward-directed) movement and budding of viral particles. We will determine the effects of infection or Gag expression on Kif4:EB1 complex formation and function in MT stabilization during distinct phases of infection, and define the domains in Gag that mediate interactions with Kif4:EB1 complexes to determine how this viral protein affects complex formation and/or activity. Finally, we will determine how upstream host signal pathways regulate these events and their potential role as targets for viral manipulation of MTs. This work takes advantage of working closely with members of this PPG with expertise in cytoskeletal regulation, motor-based virion movement, live imaging and cell signaling, as well as using the Imaging Core to develop a detailed real-time image of how HIV-1 exploits specific host MT subsets and their regulators to infect cells. The potent suppression of HIV-1 infection we observe by targeting highly specialized MT regulators suggests that new antiviral therapeutics for HIV-1 could be developed based on a better understanding of MT function, while our studies using viral systems will also have important implications for our general understanding of MT regulation and cargo transport.