Inactivation of the small GTP binding protein Rho induces multinucleate cell formation and apoptosis in murine T lymphoma EL4
Moorman, J.P.; Bobak, D.A.; Hahn, C.S.
Journal of Immunology 156(11): 4146-4153
1996
ISSN/ISBN: 0022-1767 PMID: 8666781 Document Number: 459631
The small G-protein Rho regulates the actin microfilament-dependent cytoskeleton. Exoenzyme C3 of Clostridium botulinum ADP-ribosylates Rho at Asn-41, a modification that functionally inactivates Rho. Using a Sindbis virus-based transient gene expression system, we studied the role of Rho in murine EL4 T lymphoma cells. We generated a double subgenomic infectious Sindbis virus (dsSIN:C3) recombinant which expressed C3 in gt 95% of EL4 cells. This intracellular C3 resulted in modification and inactivation of virtually all endogenous Rho. dsSIN:C3 infection led to the formation of multinucleate cells, likely by inhibiting the actin microfilament-dependent step of cytokinesis. intriguingly, in spite of the inhibition of cytokinesis, karyokinesis continued, with the result that cells containing a nuclear DNA content as high as 16N (eight nuclei) were observed. In addition, dsSIN:C3-mediated inactivation of Rho was a potent activator of apoptosis in EL4 cells. To discern whether the formation of multinucleate cells was responsible for the activation of apoptosis, 5-fluorouracil (5-FUra) was used to induce cell cycle arrest. As expected, EL4 cells treated with 5-FUra were prevented from forming multinucleate cells upon infection with dsSIN:C3. dsSIN:C3 infection, however, still caused marked apoptosis in 5-FUra-treated cells, indicating that this activation of apoptosis was independent of multinucleate cell formation.