Macrophage colony-stimulating factor (rM-CSF) stimulates pinocytosis in bone marrow-derived macrophages.

Abstract

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.

Acidosis Improves Uptake of Antigens and MHC Class I-Restricted Presentation by Dendritic Cells

“…These contrasting results could be explained considering that the mechanisms that regulate endocytosis might differ in different cells. Supporting this possibility it has been described that, not only the routes for macropinocytosed Ags, but also the sensitivity of macropinocytosis to microtubule and microfilament destabilizing drugs differ between professional phagocytes and other cell types (38,59,(61)(62)(63). However, our observations made in bicarbonate-free medium support that, as observed in other cell types, acidification of cytosol exerts an inhibitory effect on DC endocytosis.…”

CD4+CD25+ Treg induction by an HSP60‐derived peptide SJMHE1 from Schistosoma japonicum is TLR2 dependent

“…The BMMf were derived by culturing BM cells in complete DMEM containing 2 mM glutamine, 50 U/mL penicillin, 50 mg/mL streptomycin, 10% FCS (Gibco, Gaithersburg, MD, USA) and 1 ng/mL recombinant macrophage colony stimulating factor (Peprotech, Rocky Hill, NJ, USA). BMDC were derived by culturing in complete RPMI 1640 supplemented with 1 ng/mL recombinant granulocyte/monocyte-colony-stimulating factor and 1 ng/mL rIL-4 (Peprotech), as described previously [59,60]. Differentiation to DC and Mf was assessed by morphologic observation and detection of specific surface markers by FCM.…”

Targeting of Salmonella typhimurium to vesicles containing lysosomal membrane glycoproteins bypasses compartments with mannose 6-phosphate receptors.

“…Macropinosomes are large vacuoles formed as a result of massive uptake of the extracellular fluid. Macropinosomes can be induced by cell activation with macrophage colony-stimulating factor (MCS-F) or phorbol myristate (Racoosin and Swanson, 1989), or during S. typhimurium invasion of phagocytic and non-phagocytic cells (Alpuche-Aranda et al, 1994;Garcia-del Portillo and Finlay, 1994a). The recent study of Racoosin and Swanson (1993) has shown that fusion of macropinosomes with lgpcontaining compartments in macrophages is initiated as early as 4 min after macropinosome formation.…”