The Dynactin Complex Enhances the Speed of Microtubule-Dependent Motions of Adenovirus Both Towards and Away from the Nucleus

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.

Endosomophagy clears disrupted early endosomes but not virus particles during virus entry into cells     

“…1D). These results were in agreement with earlier notions that HAdV escapes quickly from endosomes and is transported by dynein/dynactin mediated processes toward the nucleus [50] [51] [52]. Protein VI on the other hand likely remains membrane associated, and may be sorted separately for degradation [26] [53].…”

The nuclear export factor CRM1 controls juxta-nuclear microtubule-dependent virus transport

“…They enter epithelial cells by receptor-mediated endocytosis (Meier et al, 2002;Wolfrum and Greber, 2013), disrupt the endosomal membrane and escape as membrane-free particles into the cytosol (Luisoni et al, 2015;Moyer et al, 2011). The transport of adenovirus towards the microtubule-organizing center (MTOC, often located near the nucleus) depends on the dynein-dynactin motor complex (Bremner et al, 2009;Engelke et al, 2011;Kelkar et al, 2006Kelkar et al, , 2004Leopold et al, 2000;Suomalainen et al, 1999). It is enhanced by cell signaling, such as p38 MAPK family signaling and protein kinase A (PKA) signaling pathways, which are activated by incoming virions (Wolfrum and Greber, 2013), together with the ERK1 and ERK2 pathway (ERK1/2, also known as MAPK3 and MAPK1, respectively) (Bruder and Kovesdi, 1997).…”

Uncoating of non-enveloped viruses

“…It engages microtubule-associated motors for movement to the nuclear envelope [69][70][71][72]. Virus docks at the cytoplasmic side of the nuclear pore complex (NPC) by binding to the nucleoporin Nup214, and undergoes final disassembly [58,73].…”