A class VII unconventional myosin is required for phagocytosis.
BACKGROUND
Phagocytosis, the process by which cells internalize particles, is essential for the defense of multicellular organisms against invading pathogens and is the major means by which many unicellular organisms obtain nutrients. The actin cytoskeleton plays a critical role in phagocytosis and the observation that a significant amount of force (10-20 nN) is generated during internalization, suggests that a myosin participates in the process. Although more than 15 distinct classes of myosin have been identified, their roles in phagocytosis are unknown.


RESULTS
The identification of a class VII unconventional myosin (DdMVII) in the Dictyostelium discoideum amoeba, which is a model for phagocytosis, is reported here. Mutant cells lacking DdMVII exhibited an 80% decrease in the uptake of particles whereas all other actin-based behaviors that were tested, including pinocytosis, exocytosis, cytokinesis and morphogenesis, proceeded normally. The defect in phagocytosis was neither because of altered particle binding nor inability to form actin-filled phagocytic cups.


CONCLUSIONS
Molecular genetic analysis of Dictyostelium myosin VII reveals that this motor protein plays a specific and significant role in phagocytosis.
Titus
M A
MA
Department of Genetics, University of Minnesota, Minneapolis, 55455, USA. titus@lenti.med.umn.edu
D000199:Actins / Q000502:physiology; D000818:Animals; D001422:Bacterial Adhesion; D001704:Biopolymers; D004023:Dictyostelium / Q000235:genetics / Q000502:physiology*; D011992:Endosomes / Q000502:physiology; D005089:Exocytosis; D018390:Gene Targeting; D017125:Genes, Protozoan; D008247:Lysosomes / Q000502:physiology; D020409:Molecular Motor Proteins / Q000502:physiology*; D009218:Myosins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D010587:Phagocytosis / Q000502:physiology*; D010588:Phagosomes / Q000502:physiology; D010873:Pinocytosis; D015800:Protozoan Proteins / Q000235:genetics / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D012441:Saccharomyces cerevisiae; D012475:Salmonella / Q000502:physiology; D013314:Stress, Mechanical
D000199:Actins; D001704:Biopolymers; D020409:Molecular Motor Proteins; D015800:Protozoan Proteins; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; C407348:myosin VII protein, Dictyostelium discoideum; D009218:Myosins