Abstract
Unlike transport vesicles or organelles, human adenovirus (HAdV) directly binds to the microtubule minus end-directed motor dynein for transport to the nucleus. The dynein cofactor dynactin enhances nuclear transport of HAdV and boosts infection. To determine if dynactin has a specific role in cytoplasmic trafficking of incoming HAdV on microtubules, we used live cell spinning disc confocal microscopy at 25 Hz acquisition frequency and automated tracking of single virus particles at 20–50 nm spatial resolution. Computational dissection by machine-learning algorithms extracted specific motion patterns of viral trajectories. We found that unperturbed cells supported two kinds of microtubule-dependent motions, directed motions (DM) and fast drifts (FD). DM had speeds of 0.2 to 2 μm/s and run lengths of 0.4 up to 7 μm, while FD were slower and less extensive at 0.02 to 0.4 μm/s and 0.05 to 2.5 μm. Dynactin interference by overexpression of p50/dynamitin or a coiled-coil domain of p150/Glued reduced the speeds and amounts of both center- and periphery-directed DM but not FD, and inhibited infection. These results indicate that dynactin enhances adenovirus infection by increasing the speed and efficiency of dynein-mediated virus motion to the nucleus, and, surprisingly, also supports a hereto unknown motor activity for virus transport to the cell periphery.
Highlights
Viruses receive extensive assistance from the host cells for infection
In control cells we found so-called directed motion (DM) segments, which were composed of unidirectional steps and had rather high overall speeds of 0.2 to 2 μm/s and long run lengths of 0.4 up to 7 μm (Figure 2b, Figure 5c)
Both types of motors are simultaneously bound to the cargo, but only one type is active during directional motion runs, or one type of motor is more abundant on the cargo than the other
Summary
They utilize receptors for attachment and movement on the cell surface [1], or employ signaling machineries and endocytic pathways; for reviews, see [2,3,4] They escape to the cytosol by membrane fusion in the case of enveloped viruses [5], or membrane disruption in the case of nonenveloped viruses [6]. Cytoplasmic dynein is responsible for a broad range of cellular functions, including transport of organelles and regulation of mitosis [12,13,14] It is a large protein complex composed of different subunits, and moves in the range of μm/s towards microtubule minus ends, which are organized in the centrosome near the nucleus of nonpolarized or migratory cells [15]. The usage of multiple motors might be advantageous for viruses, which utilize the nucleus for genome replication. Such viruses comprise influenza viruses, herpes viruses or small DNA-tumor viruses, such as human and animal polyomaviruses, papillomaviruses and human adenoviruses (HAdV)
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