Cortactin promotes cell motility by enhancing lamellipodial persistence.
BACKGROUND
Lamellipodial protrusion, which is the first step in cell movement, is driven by actin assembly and requires activity of the Arp2/3 actin-nucleating complex. However, it is unclear how actin assembly is dynamically regulated to support effective cell migration.


RESULTS
Cells deficient in cortactin have impaired cell migration and invasion. Kymography analyses of live-cell imaging studies demonstrate that cortactin-knockdown cells have a selective defect in the persistence of lamellipodial protrusions. The motility and protrusion defects are fully rescued by cortactin molecules, provided both the Arp2/3 complex and F-actin binding sites are intact. Consistent with this requirement for simultaneous contacts with Arp2/3 and F-actin, cortactin is recruited by Arp2/3 complex to lamellipodia and binds with a higher affinity to ATP/ADP-Pi-F-actin than to ADP-F-actin. In situ labeling of lamellipodia revealed that the relative levels of free barbed ends of actin filaments are reduced by over 30% in the cortactin-knockdown cells; however, there is no change in Arp2/3-complex localization to lamellipodia. Cortactin-knockdown cells also have a selective defect in the assembly of new adhesions in protrusions, as assessed by analysis of GFP-paxillin dynamics in living cells.


CONCLUSIONS
Cortactin enhances lamellipodial persistence, at least in part through regulation of Arp2/3 complex. The presence of cortactin also enhances the rate of new adhesion formation in lamellipodia. In vivo, these functions may be important during directed cell motility.
Bryce
Nicole S
NS
Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
Clark
Emily S
ES
Leysath
Ja'Mes L
JL
Currie
Joshua D
JD
Webb
Donna J
DJ
Weaver
Alissa M
AM
D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001483:Base Sequence; D015153:Blotting, Western; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology*; D051356:Cortactin; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D006801:Humans; D007734:Kymography; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D011485:Protein Binding; D011554:Pseudopodia / Q000378:metabolism*
C495926:ACTR2 protein, human; C495928:ACTR3 protein, human; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; C495868:CTTN protein, human; D051356:Cortactin; D003598:Cytoskeletal Proteins; D008840:Microfilament Proteins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate