Effects of clostridium botulinum C2 toxin and cytochalasin D on in vitro invasiveness, motility and F-actin content of a murine T-lymphoma cell line.

In order to investigate the role of microfilaments in the crawling movements of lymphoid cells, we have analyzed the effects of botulinum C2 toxin and of cytochalasin D (cytoD) on the actin cytoskeleton and on the motility of a BW5147 T-lymphoma-derived cell line. Actin was ADP-ribosylated by C2 toxin in the living cells, and this resulted in a time and dose-dependent disappearance of F-actin, as assessed by staining with labeled phalloidin. CytoD did not affect the amount of polymerized actin, but rather changed its distribution from a diffuse peripheral network to focal accumulations on one side of the cell. Both treatments affected the motility of the lymphoma cells in two assay systems. Fourier analysis was used to quantify shape changes performed by the cells. C2 toxin as well as CytoD caused the cessation of pseudopodal protrusion. Invasion of the lymphoma cells through a monolayer of fibroblast-like cells was also inhibited by the treatments, in a dose-dependent way. C2 toxin significantly inhibited invasion at concentrations at which only part of the actin pool had been ADP-ribosylated. We conclude that partial depolymerization, as well as disorganization, of the microfilament network impairs the active cellular deformations that are involved in the crawling movements of the lymphoma cells. From previous work, there is evidence to state that the monolayer invasion assay to some extent mimics tissue infiltration by hematopoietic cells. The present study is the first to analyze the role of actin polymerization in a model system that is relevant for the migration of lymphoid cells in vivo.