Distinct acto/myosin-I structures associate with endocytic profiles at the plasma membrane.
Endocytosis in yeast requires actin and clathrin. Live cell imaging has previously shown that massive actin polymerization occurs concomitant with a slow 200-nm inward movement of the endocytic coat (Kaksonen, M., Y. Sun, and D.G. Drubin. 2003. Cell. 115:475-487). However, the nature of the primary endocytic profile in yeast and how clathrin and actin cooperate to generate an endocytic vesicle is unknown. In this study, we analyze the distribution of nine different proteins involved in endocytic uptake along plasma membrane invaginations using immunoelectron microscopy. We find that the primary endocytic profiles are tubular invaginations of up to 50 nm in diameter and 180 nm in length, which accumulate the endocytic coat components at the tip. Interestingly, significant actin labeling is only observed on invaginations longer than 50 nm, suggesting that initial membrane bending occurs before initiation of the slow inward movement. We also find that in the longest profiles, actin and the myosin-I Myo5p form two distinct structures that might be implicated in vesicle fission.
Idrissi
Fatima-Zahra
FZ
Instituto de Biología Molecular de Barcelona, Consejo Superior de Investigaciones Científicas, 08028 Barcelona, Spain.
Grötsch
Helga
H
Fernández-Golbano
Isabel M
IM
Presciatto-Baschong
Cristina
C
Riezman
Howard
H
Geli
María-Isabel
MI
D008841:Actin Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D000199:Actins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D003599:Cytoskeleton / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology; D016253:Microscopy, Immunoelectron; D024461:Myosin Type I / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000378:metabolism* / Q000648:ultrastructure; D022161:Transport Vesicles / Q000378:metabolism* / Q000648:ultrastructure
D000199:Actins; D024461:Myosin Type I