Stimulation of cell motility by a viral fibroblast growth factor homolog: proposal for a role in viral pathogenesis.

The Autographa californica M nucleopolyhedrovirus (AcMNPV) encodes a gene (open reading frame 32) with homology to vertebrate and invertebrate fibroblast growth factors (fgfs), key regulators of developmental processes affecting the growth, differentiation, and migration of many cell types. We studied the temporal regulation of the AcMNPV fgf, vfgf, by Northern (RNA) blot hybridization; vfgf was transcribed as a 0.6-kb mRNA at early times but as part of a 1.4-kb bicistronic mRNA at late times. The product of vfgf, vFGF, exhibited a number of characteristics that have also been demonstrated for other FGF homologs. vFGF had strong affinity to heparin, a property important for FGF signaling via an FGF receptor. vFGF was secreted into the extracellular fluid when expressed in insect cells, suggesting that it acts as an extracellular ligand. Finally, vFGF was able to stimulate migration of several different types of insect cells. We discuss how this activity may be important for its function during virus infection.