Actin rearrangement-inducing factor of baculoviruses is tyrosine phosphorylated and colocalizes to F-actin at the plasma membrane.
In previous studies we have identified actin rearrangement-inducing factor 1 as an early gene product of Autographa californica multicapsid nuclear polyhedrosis virus that is involved in the remodeling of the actin cytoskeleton. We have constructed viral recombinants with a mutated Arif-1 open reading frame that confirm the causal link of Arif-1 expression and the actin rearrangement observed as accumulation of F-actin at the plasma membrane at 3 to 7 h postinfection. Infection with Arif mutant viruses leads to the loss of actin accumulation at the plasma membrane in TN-368 cells, although in the course of infection, early actin cables and nuclear F-actin are observed as in wild-type-infected cells. By immunofluorescence studies, we have demonstrated the localization of Arif-1 at the plasma membrane, and confocal imaging reveals the colocalization to F-actin. Accordingly, the approximately 47-kDa Arif-1 protein is observed exclusively in membrane fractions prepared at 4 to 48 h postinfection, with a decrease at 24 h postinfection. Phosphatase treatment suggests that Arif-1 is modified by phosphorylation. Antibodies against phosphotyrosine precipitate Arif-1 from membrane fractions, indicating that Arif-1 becomes tyrosine phosphorylated during the early and late phases of infection. In summary, our results indicate that functional Arif-1 is tyrosine phosphorylated and is located at the plasma membrane as a component of the actin rearrangement-inducing complex.
Max Planck Institute for Neurological Research and Department of Neurology, University of Cologne, Cologne, Germany.
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Dreschers
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Roncarati
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Knebel-Mörsdorf
D000199:Actins / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D007150:Immunohistochemistry; D008565:Membrane Proteins; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D017924:Nucleopolyhedroviruses / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism*; D018411:Spodoptera / Q000821:virology; D013997:Time Factors; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
C108376:AcOrf-20 protein, Autographa californica nucleopolyhedrovirus; D000199:Actins; D008565:Membrane Proteins; D010750:Phosphoproteins; D014764:Viral Proteins; D019000:Phosphotyrosine