Macrophage colony-stimulating factor (rM-CSF) stimulates pinocytosis in bone marrow-derived macrophages.
Incubation of murine bone marrow-derived macrophages (BMM) in medium containing recombinant macrophage colony-stimulating factor (rM-CSF) stimulated influx, efflux, and the net accumulation of the fluid-phase pinocytic marker, lucifer yellow (LY). Stimulation was dose dependent, occurred within 5 min of addition of the growth factor, and was sustained. Previous experiments had shown that BMM treated with PMA were stimulated to accumulate LY, but compared with rM-CSF-treated cells, the onset of stimulation in PMA-treated macrophages was slower. In further comparisons of rM-CSF- and PMA-stimulated LY accumulation, it was found that rM-CSF-stimulated pinocytosis could be abolished by pretreatment with 0.5 mg/ml trypsin, whereas neither unstimulated nor PMA-stimulated LY accumulation was affected by trypsin pretreatment. These findings indicate that the rM-CSF response was initiated at the cell surface, while the PMA response occurred via intracellular (or trypsin-resistant) receptors. However, once initiated, the pinocytic responses elicited by either agent were very similar. First, rM-CSF-treated cells, like PMA-treated cells, showed extensive ruffling and formation of large phase-bright pinosomes. Second, both rM-CSF- and PMA-stimulated LY accumulation could be inhibited by treatment of cells with the cytoskeleton destabilizing drugs nocodazole, colchicine, or cytochalasin D. Finally, rM-CSF, like PMA, was found to stimulate efflux of LY from cells preloaded with the dye. Thus, both rM-CSF and PMA stimulate the net rate of solute flow through the macrophage endocytic compartment.
Racoosin
E L
EL
Department of Anatomy and Cellular Biology, Harvard Medical School, Boston, Massachusetts 02115.
Swanson
J A
JA
D008841:Actin Cytoskeleton / Q000187:drug effects; D000818:Animals; D001854:Bone Marrow Cells; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D003115:Colony-Stimulating Factors / Q000494:pharmacology*; D066298:In Vitro Techniques; D007546:Isoquinolines; D016173:Macrophage Colony-Stimulating Factor; D008264:Macrophages / Q000166:cytology / Q000502:physiology*; D051379:Mice; D008809:Mice, Inbred C3H; D008870:Microtubules / Q000187:drug effects; D010873:Pinocytosis / Q000187:drug effects*; D011994:Recombinant Proteins; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014357:Trypsin / Q000494:pharmacology
D003115:Colony-Stimulating Factors; D007546:Isoquinolines; D011994:Recombinant Proteins; D016173:Macrophage Colony-Stimulating Factor; C017475:lucifer yellow; D014357:Trypsin; D013755:Tetradecanoylphorbol Acetate