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J. Exp. Med.,
Volume 186, Number 9, November 3, 1997 1487-1494
By

From the * Pulmonary Division, Department of Medicine, Columbia University College of Physicians
and Surgeons, New York 10032; and Specific pathways linking heterotrimeric G proteins and Fc
Department of Immunology and Department of Cell Biology,
Scripps Research Institute, La Jolla, California 92037
receptors to the actin-based cytoskeleton are poorly understood. To test a requirement for Rho family members in cytoskeletal
events mediated by structurally diverse receptors in leukocytes, we transfected the full-length
human chemotactic peptide receptor in RAW 264.7 cells and examined cytoskeletal alterations
in response to the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (FMLP), colony stimulating factor-1 (CSF-1), IgG-coated particles, and phorbol 12-myristate 13-acetate
(PMA). Expression of Rac1 N17, Cdc42 N17, or the GAP domain of n-chimaerin inhibited
cytoskeletal responses to FMLP and CSF-1, and blocked phagocytosis. Accumulation of F-actin-
rich "phagocytic cups" was partially inhibited by expression of Rac1 N17 or Cdc42 N17. In
contrast, PMA-induced ruffling was not inhibited by expression of Rac1 N17, but was blocked
by expression of Cdc42 N17, indicating that cytoskeletal inhibition by these constructs was
nonoverlapping. These results demonstrate differential requirements for Rho family GTPases
in leukocyte motility, and indicate that both Rac1 and Cdc42 are required for Fc
receptor-
mediated phagocytosis and for membrane ruffling mediated by structurally distinct receptors in
macrophages.
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