Gadkin negatively regulates cell spreading and motility via sequestration of the actin-nucleating ARP2/3 complex.
Regulation of actin dynamics is key to many cell physiological processes, ranging from protrusion formation and control of cell shape to cellular motility, endocytosis, and vesicle movement. The actin-related protein (ARP)2/3 complex is a major actin nucleator organizing branched filament networks in lamellipodial protrusions and during cell migration downstream of nucleation-promoting factors (NPFs). Although many NPFs have been characterized in detail, only few ARP2/3 inhibitors are known. Here, we identify the trans-Golgi network (TGN)/endosomally localized adaptor protein (AP)-1-associated adaptor protein Gadkin as a negative regulator of ARP2/3 function. Loss of Gadkin is associated with a partial redistribution of ARP2/3 to the plasma membrane and with increased cell spreading and migration, phenotypes that depend on the presence of a functional ARP2/3 complex. Gadkin directly binds to ARP2/3 via a conserved tryptophan-based acidic cluster motif reminiscent of ARP2/3-binding sequences of NPFs but fails to facilitate ARP2/3-mediated actin assembly. Consistent with an inhibitory role of Gadkin on ARP2/3 function, ARP2/3 is found on motile Gadkin-containing endosomal vesicles under migration-inhibiting conditions from where it relocalizes to the plasma membrane following activation of NPFs. Together with the observation that Gadkin-mediated inhibition of cell spreading requires its binding to ARP2/3, these data indicate that Gadkin is a negative regulator of ARP2/3 function present on intracellular membranes.
Laboratory of Membrane Biochemistry, Institute of Chemistry and Biochemistry, Freie Universität Berlin and NeuroCure Cluster of Excellence, 14195 Berlin, Germany. tmaritzen@googlemail.com
Tanja
T
Maritzen
Tobias
T
Zech
Michael R
MR
Schmidt
Eberhard
E
Krause
Laura M
LM
Machesky
Volker
V
Haucke
D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology*; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid
D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D008565:Membrane Proteins; C574966:gadkin protein, mouse