RRC ID 28980
Author Novak KD, Peterson MD, Reedy MC, Titus MA.
Title Dictyostelium myosin I double mutants exhibit conditional defects in pinocytosis.
Journal J. Cell Biol.
Abstract The functional relationship between three Dictyostelium myosin Is, myoA, myoB, and myoC, has been examined through the creation of double mutants. Two double mutants, myoA-/B- and myoB-/C-, exhibit similar conditional defects in fluid-phase pinocytosis. Double mutants grown in suspension culture are significantly impaired in their ability to take in nutrients from the medium, whereas they are almost indistinguishable from wild-type and single mutant strains when grown on a surface. The double mutants are also found to internalize gp126, a 116-kD membrane protein, at a slower rate than either the wild-type or single mutant cells. Ultrastructural analysis reveals that both double mutants possess numerous small vesicles, in contrast to the wild-type or myosin I single mutants that exhibit several large, clear vacuoles. The alterations in fluid and membrane internalization in the suspension-grown double mutants, coupled with the altered vesicular profile, suggest that these cells may be compromised during the early stages of pinocytosis, a process that has been proposed to occur via actin-based cytoskeletal rearrangements. Scanning electron microscopy and rhodamine-phalloidin staining indicates that the myosin I double mutants appear to extend a larger number of actin-filled structures, such as filopodia and crowns, than wild-type cells. Rhodamine-phalloidin staining of the F-actin cytoskeleton of these suspension-grown cells also reveals that the double mutant cells are delayed in the rearrangement of cortical actin-rich structures upon adhesion to a substrate. We propose that myoA, myoB, and myoC play roles in controlling F-actin filled membrane projections that are required for pinosome internalization in suspension.
Volume 131(5)
Pages 1205-21
Published 1995-12
PMID 8522584
PMC PMC2120646
MeSH Actins / metabolism Animals Dictyostelium Fungal Proteins / genetics Fungal Proteins / physiology Mutagenesis Myosin Type I* Myosins / genetics Myosins / physiology* Pinocytosis / genetics Pinocytosis / physiology* Protozoan Proteins / genetics Protozoan Proteins / physiology Vacuoles / metabolism
IF 8.784
Times Cited 155
Cellular slime molds S00036