Abstract
The baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV), a pathogen of lepidopteran insects, has a striking dependence on the host cell actin cytoskeleton during infection. During the delayed-early stage of AcMNPV infection, the virus was shown to induce the accumulation of filamentous actin at the cortex of infected cells. However, the dynamics and molecular mechanism of cortical actin assembly remained unknown. Using live cell imaging, we show that AcMNPV induces the formation of dynamic dot-like actin structures that are arranged in clusters, resembling clusters of invadosomes in mammalian cells. Furthermore, we find that the AcMNPV protein actin-rearrangement-inducing factor-1 (ARIF-1), which was previously shown to be necessary and sufficient for assembly of cortical actin and efficient viral infection in insect hosts, is both necessary and sufficient for invadosome-like structure formation. We mapped the regions of ARIF-1 required for invadosome-like structure formation to a segment of the predicted C-terminal cytoplasmic region, and further identified residues tyrosine 332 and proline 335 as being required for organizing clusters of invadosome-like structures. Additionally, we found that ARIF-1 and the invadosome-associated proteins cortactin and the Arp2/3 complex localize to invadosome-like structures, and structure formation requires Arp2/3 complex activity. The resemblance of ARIF-1-induced structures to invadosomes in mammalian cells, and the known role of such structures in extracellular matrix degradation, suggests that AcMNPV-induced invadosome-like structures accelerate viral spread through the insect body by degrading extracellular matrix barriers during infection.
Competing Interest Statement
The authors have declared no competing interest.
