Annexin 2 has an essential role in actin-based macropinocytic rocketing.
Annexin 2 is a Ca(2+) binding protein that binds to and aggregates secretory vesicles at physiological Ca(2+) levels [1] and that also associates Ca(2+) independently with early endosomes [2, 3]. These properties suggest roles in both exocytosis and endocytosis, but little is known of the dynamics of Annexin 2 distribution in live cells during these processes. We have used evanescent field microscopy to image Annexin 2-GFP in live, secreting rat basophilic leukemia cells and in cells performing pinocytosis. Although we found no evidence of Annexin 2 involvement in exocytosis, we observed an enrichment of Annexin 2-GFP in actin tails propeling macropinosomes. The association of Annexin 2-GFP with rocketing macropinosomes was specific because Annexin 2-GFP was absent from the actin tails of rocketing Listeria. This finding suggests that the association of Annexin 2 with macropinocytic rockets requires native pinosomal membrane. Annexin 2 is necessary for the formation of macropinocytic rockets since overexpression of a dominant-negative Annexin 2 construct abolished the formation of these structures. The same construct did not prevent the movement of Listeria in infected cells. These results show that recruitment of Annexin 2 to nascent macropinosome membranes 16656is an essential prerequisite for actin polymerization-dependent vesicle locomotion.
Merrifield
C J
CJ
Vollum Institute, 3181 Sam Jackson Park Road, Oregon 97201, USA.
Rescher
U
U
Almers
W
W
Proust
J
J
Gerke
V
V
Sechi
A S
AS
Moss
S E
SE
D000199:Actins / Q000502:physiology*; D000818:Animals; D017306:Annexin A2 / Q000502:physiology*; D005089:Exocytosis / Q000502:physiology; D018613:Microscopy, Confocal; D009068:Movement; D009997:Osmotic Pressure; D010873:Pinocytosis / Q000502:physiology*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000502:physiology; D014407:Tumor Cells, Cultured
D000199:Actins; D017306:Annexin A2; D011993:Recombinant Fusion Proteins