Myosin-1c couples assembling actin to membranes to drive compensatory endocytosis.
Compensatory endocytosis follows regulated exocytosis in cells ranging from eggs to neurons, but the means by which it is accomplished are unclear. In Xenopus eggs, compensatory endocytosis is driven by dynamic coats of assembling actin that surround and compress exocytosing cortical granules (CGs). We have identified Xenopus laevis myosin-1c (XlMyo1c) as a myosin that is upregulated by polyadenylation during meiotic maturation, the developmental interval that prepares eggs for fertilization and regulated CG exocytosis. Upon calcium-induced exocytosis, XlMyo1c is recruited to exocytosing CG membranes where actin coats then assemble. When XlMyo1c function is disrupted, actin coats assemble, but dynamic actin filaments are uncoupled from the exocytosing CG membranes such that coats do not compress, and compensatory endocytosis fails. Remarkably, there is also an increase in polymerized actin at membranes throughout the cell. We conclude that XlMyo1c couples polymerizing actin to membranes and so mediates force production during compensatory endocytosis.
Sokac
Anna M
AM
Program in Cellular and Molecular Biology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Schietroma
Cataldo
C
Gundersen
Cameron B
CB
Bement
William M
WM
D000199:Actins / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D004705:Endocytosis; D005089:Exocytosis; D005260:Female; D066298:In Vitro Techniques; D008540:Meiosis; D008969:Molecular Sequence Data; D024461:Myosin Type I / Q000502:physiology*; D009218:Myosins / Q000378:metabolism / Q000502:physiology*; D009865:Oocytes / Q000378:metabolism; D026723:Polyadenylation; D011485:Protein Binding; D022142:Secretory Vesicles / Q000378:metabolism; D015854:Up-Regulation; D029867:Xenopus Proteins / Q000378:metabolism / Q000502:physiology*; D014982:Xenopus laevis / Q000378:metabolism / Q000502:physiology*
D000199:Actins; D029867:Xenopus Proteins; C515861:myosin-1c, Xenopus; D024461:Myosin Type I; D009218:Myosins; D002118:Calcium