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.
Office of Clinical Research and Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA.
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Carballo
D M
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Pitterle
D J
DJ
Stumpo
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RT
Sperling
P J
PJ
Blackshear
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