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Molecular and Cellular Biology, August 2000, p. 5998-6007, Vol. 20, No. 16
Laboratory of Cell Biology, National Heart,
Lung, and Blood Institute, National Institutes of Health, Bethesda,
Maryland 20892
Received 21 December 1999/Returned for modification 9 February
2000/Accepted 15 May 2000
The ADP-ribosylation factor 6 (ARF6) GTPase has a dual function in
cells, regulating membrane traffic and organizing cortical actin. ARF6
activation is required for recycling of the endosomal membrane back
to the plasma membrane (PM) and also for ruffling at the
PM induced by Rac. Additionally, ARF6 at the PM induces the formation
of actin-containing protrusions. To identify sequences in ARF6 that are
necessary for these distinct functions, we examined the behavior of a
chimeric protein of ARF1 and ARF6. The 1-6 chimera (with the amino half
of ARF1 and the carboxyl half of ARF6) localized like ARF6 in HeLa
cells and moved between the endosome and PM, but it did not form
protrusions, an ARF6 effector function. Two residues in the
amino-terminal half of ARF6, Q37 and S38, when substituted into the
1-6 chimera allowed protrusion formation, whereas removal of these
residues from ARF6 resulted in an inability to form protrusions.
Interestingly, expression of 1-6 in cells selectively inhibited
protrusions induced by wild-type ARF6 but had no effect on
ARF6-regulated membrane movement or Rac-induced ruffling. Thus, we have
uncoupled two functions of ARF6, one involved in membrane trafficking,
which is necessary for Rac ruffling, and another involved in protrusion formation.
0270-7306/00/$04.00+0
Separation of Membrane Trafficking and Actin
Remodeling Functions of ARF6 with an Effector Domain Mutant

*
Corresponding author. Mailing address: Center Dr. MSC
0301, Bldg. 3, Room B1-22, Bethesda, MD 20892. Phone: (301) 402-2907. Fax: (301) 402-1519. E-mail: jdonalds{at}helix.nih.gov.
Present address: School of Biology, Georgia Institute of
Technology, Atlanta, GA 30332-0363.
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