CSF‐1 stimulates nucleoside transport in S1 macrophages

Abstract

We have examined nucleoside transport (NT) in a cell line derived from primary day 7 murine bone marrow macrophages (S1 macrophages) in response to the macrophage growth factor, colony-stimulating factor 1 (CSF-1). Adenosine and uridine transport in quiescent S1 macrophages occurred primarily by two facilitated diffusional routes, one that was sensitive and one that was relatively resistant to the inhibitor nitrobenzylthioinosine (NBMPR). Addition of CSF-1 to quiescent cultures resulted in increased adenosine and uridine transport with biphasic kinetics with respect to the cell cycle. Basal NT activity was elevated (about twofold) within 15 min of CSF-1 addition, returned to near basal levels by 1 h, and then increased again (three- to fourfold) 8-12 h later, returning again to basal levels by 48 h post CSF-1 stimulation. We propose that the large increase in NT activity at 8-12 h corresponded with the time when cultures synchronously began to enter the S phase of the cell cycle. In addition to these changes in the absolute rates, the proportions of NBMPR-sensitive and NBMPR-insensitive transport also change after CSF-1 addition. Quiescent cultures exhibited primarily NBMPR-insensitive transport while logrithmically growing cultures exhibited primarily NBMPR-sensitive nucleoside transport activity. The increase in the NBMPR-sensitive component of the transport process paralleled a similar increase in the number of high-affinity NBMPR binding sites, suggesting that the mechanism for upregulating NBMPR-sensitive NT activity involves increases in the number of NBMPR-sensitive transporter sites. Interestingly, we were unable to detect Na(+)-dependent concentrative uptake of adenosine, uridine, or formycin-B either in the S1 macrophage cell line or in primary (day 7) murine macrophages. Thus these bone marrow derived macrophages did not display the characteristically large Na(+)-dependent transport systems observed by others in peritoneal macrophages, implying that these two populations of macrophages are, indeed, functionally distinct.

The equilibrative nucleoside transporter family, SLC29

“…Although expression of the mouse HNP36 splice variant is greatly enhanced by treatment of quiescent fibroblasts with serum or growth factors as part of the delayed-early response [49], similar regulation of hENT2 has not been detected [9]. Moreover, while colony stimulating factor has been reported to stimulate es-type transport activity, presumably mediated by mENT1, in a mouse macrophage cell line no changes in ei-type activity were observed [27], and so a role for ENT2 in the proliferative response remains unclear.…”

Cloning of the Human Equilibrative, Nitrobenzylmercaptopurine Riboside (NBMPR)-insensitive Nucleoside Transporter ei by Functional Expression in a Transport-deficient Cell Line

“…2 We have also been unable to detect regulation of ENT2 in phytohemagglutinin/interleukin-2-stimulated peripheral blood lymphocytes. Furthermore, previous studies of nucleoside transport in a bone marrow-derived murine macrophage cell line have demonstrated colony stimulating factor 1 stimulation of es transport activity (ENT1) with no change in ei transport activity (ENT2) (25). Thus, a role for the ENT2 nucleoside transporter in the proliferative response is unclear and will require further study.…”

Characterization of a Novel Na+-dependent, Guanosine-specific, Nitrobenzylthioinosine-sensitive Transporter in Acute Promyelocytic Leukemia Cells

“…Other cell lines such as L1210 murine leukemia cells and IEC-6 mouse intestinal epithelial cells, express multiple transporters, including equilibrative and concentrative transporters, simultaneously (18,15). As well, NT activities within the same cell type have been observed to change with changes in growth state (26,27), differentiation (21,(32)(33)(34)(35)(36)(37), and neoplastic transformation (28). For example, induction of monocytic (21,35) or neutrophilic differentiation (33,34) of HL-60 human leukemia cells leads to a decrease in es nucleoside transport activity and increased Na ϩ -dependent nucleoside transport activity (33)(34)(35).…”