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 1995-12-1
DOI 10.1083/jcb.131.5.1205
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 8.811
Times Cited 161
Cellular slime molds S00036