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Published on: February 14, 2016
Poxvirus A51R Proteins Negatively Regulate Microtubule-Dependent Transport by Kinesin-1
Dahee Seo1, Yang Yue2, Shin Yamazaki3
1Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Abstract:
Microtubule (MT)-dependent transport is a critical means of intracellular movement of cellular cargo by kinesin and dynein motors. MT-dependent transport is tightly regulated by cellular MT-associated proteins (MAPs) that directly bind to MTs and either promote or impede motor protein function. Viruses have been widely shown to usurp MT-dependent transport to facilitate their virion movement to sites of replication and/or for exit from the cell. However, it is unclear if viruses also negatively regulate MT-dependent transport. Using single-molecule motility and cellular transport assays, we show that the vaccinia virus (VV)-encoded MAP, A51R, inhibits kinesin-1-dependent transport along MTs in vitro and in cells. This inhibition is selective as the function of kinesin-3 is largely unaffected by VV A51R. Interestingly, we show that A51R promotes the perinuclear accumulation of cellular cargo transported by kinesin-1 such as lysosomes and mitochondria during infection. Moreover, A51R also regulates the release of specialized VV virions that exit the cell using kinesin-1-dependent movement. Using a fluorescently tagged rigor mutant of kinesin-1, we show that these motors accumulate on A51R-stabilized MTs, suggesting these stabilized MTs may form a "kinesin-1 sink" to regulate MT-dependent transport in the cell. Collectively, our findings uncover a new mechanism by which viruses regulate host cytoskeletal processes.
Insights
The vaccinia virus protein A51R inhibits kinesin-1 transport, impacting cellular cargo movement and viral release. This viral MAP creates a "kinesin-1 sink" on microtubules, regulating intracellular transport during infection.
Area of Science:
- Cell Biology
- Virology
- Molecular Motors
Background:
- Microtubule (MT)-dependent transport is essential for intracellular cargo movement mediated by kinesin and dynein motors.
- MT-associated proteins (MAPs) regulate motor protein function, and viruses often hijack this transport system.
- It remains largely unknown if viruses actively inhibit MT-dependent transport.
Purpose of the Study:
- To investigate whether viruses can negatively regulate MT-dependent transport.
- To determine the role of the vaccinia virus (VV)-encoded MAP, A51R, in regulating intracellular transport.
Main Methods:
- Single-molecule motility assays to assess motor protein function in vitro.
- Cellular transport assays to observe cargo movement within infected cells.
- Utilized a fluorescently tagged rigor mutant of kinesin-1 to visualize motor protein behavior.
Main Results:
- VV-encoded A51R selectively inhibits kinesin-1-dependent transport along MTs, while kinesin-3 remains largely unaffected.
- A51R promotes the perinuclear accumulation of kinesin-1 transported cargo, including lysosomes and mitochondria.
- A51R regulates the release of VV virions via kinesin-1-dependent exit and causes kinesin-1 accumulation on stabilized MTs, forming a 'kinesin-1 sink'.
Conclusions:
- VV A51R acts as a viral MAP that inhibits kinesin-1 function.
- This inhibition disrupts cellular transport and viral egress.
- Viruses can employ novel mechanisms to manipulate host cytoskeletal dynamics for their benefit.
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