Dynamin A, Myosin IB and Abp1 couple phagosome maturation to F-actin binding.
The role of actin, class I myosins and dynamin in endocytic uptake processes is well characterized, but their role during endo-phagosomal membrane trafficking and maturation is less clear. In Dictyostelium, knockout of myosin IB (myoB) leads to a defect in membrane protein recycling from endosomes back to the plasma membrane. Here, we show that actin plays a central role in the morphology and function of the endocytic pathway. Indeed, latrunculin B (LatB) induces endosome tubulation, a phenotype also observed in dynamin A (dymA)-null cells. Knockout of dymA impairs phagosome acidification, whereas knockout of myoB delays reneutralization, a phenotype mimicked by a low dose of LatB. As a read out for actin-dependent processes during maturation, we monitored the capacity of purified phagosomes to bind F-actin in vitro, and correlated this with the presence of actin-binding and membrane-trafficking proteins. Phagosomes isolated from myoB-null cells showed an increased binding to F-actin, especially late phagosomes. In contrast, early phagosomes from dymA-null cells showed reduced binding to F-actin while late phagosomes were unaffected. We provide evidence that Abp1 is the main F-actin-binding protein in this assay and is central for the interplay between DymA and MyoB during phagosome maturation.
Départment de Biochimie, Faculté des Sciences, Université de Genève, Sciences II, 30 quai Ernest Ansermet, Geneva, Switzerland.
Navin
N
Gopaldass
Devang
D
Patel
Ramona
R
Kratzke
Regis
R
Dieckmann
Stéphanie
S
Hausherr
Monica
M
Hagedorn
Roger
R
Monroy
Julia
J
Krüger
Eva M
EM
Neuhaus
Eik
E
Hoffmann
Katja
K
Hille
Sergei A
SA
Kuznetsov
Thierry
T
Soldati
D000199:Actins / Q000378:metabolism*; D015153:Blotting, Western; D004023:Dictyostelium / Q000378:metabolism / Q000648:ultrastructure; D034281:Dynamins / Q000235:genetics / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism* / Q000648:ultrastructure; D055786:Gene Knockout Techniques; D008840:Microfilament Proteins / Q000378:metabolism*; D008954:Models, Biological; D024461:Myosin Type I / Q000235:genetics / Q000378:metabolism*; D010587:Phagocytosis; D010588:Phagosomes / Q000378:metabolism* / Q000648:ultrastructure; D021381:Protein Transport; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*
D000199:Actins; D008840:Microfilament Proteins; D015800:Protozoan Proteins; D024461:Myosin Type I; D034281:Dynamins; C117420:dynamin A protein, Dictyostelium discoideum