Phagocytic and macropinocytic activity in MARCKS-deficient macrophages and fibroblasts.
Macrophages express high levels of the myristoylated, alanine-rich, C kinase substrate (MARCKS), an actin cross-linking protein. To investigate a possible role of MARCKS in macrophage function, fetal liver-derived macrophages were generated from wild-type and MARCKS knockout mouse embryos. No differences between the wild-type and MARCKS-deficient macrophages with respect to morphology (Wright's stain) or actin distribution (staining with rhodamine-phalloidin, under basal conditions or after treatment with phorbol esters, lipopolysaccharide, or both) were observed. We then evaluated phagocytosis mediated by different receptors: Fc receptors tested with IgG-coated sheep red blood cells, complement C3b receptors tested with C3b-coated yeast, mannose receptors tested with unopsonized zymosan, and nonspecific phagocytosis tested with latex beads. We also studied fluid phase endocytosis in macrophages and mouse embryo fibroblasts by using FITC-dextran to quantitate this process. In most cases, there were no differences between the cells derived from wild-type and MARCKS-deficient mice. However, a minor but significant and reproducible difference in rates of zymosan phagocytosis at 45-60 min was observed, with lower rates of phagocytosis in the MARCKS-deficient cells. Our data indicate that MARCKS deficiency may lead to slightly decreased rates of zymosan phagocytosis.
Carballo
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E
Office of Clinical Research and Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA.
Pitterle
D M
DM
Stumpo
D J
DJ
Sperling
R T
RT
Blackshear
P J
PJ
D000199:Actins / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D004622:Embryo, Mammalian / Q000166:cytology; D005347:Fibroblasts / Q000378:metabolism / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000166:cytology / Q000196:embryology; D008264:Macrophages / Q000378:metabolism / Q000502:physiology*; D008565:Membrane Proteins; D051379:Mice; D018345:Mice, Knockout / Q000235:genetics; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D010587:Phagocytosis / Q000502:physiology*; D010873:Pinocytosis / Q000502:physiology*; D011506:Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013194:Staining and Labeling
D000199:Actins; D047908:Intracellular Signaling Peptides and Proteins; C000619711:Marcks protein, mouse; D008565:Membrane Proteins; D011506:Proteins; D000076250:Myristoylated Alanine-Rich C Kinase Substrate