Cell growth and differentiation in vitro in mouse macrophages transformed by a tsA mutant of simian virus40. I. Cellular response in proliferative and phagocytic activities to the shift of temperature differs depending on the culture state in mouse bone marrow cells transformed by the tsA640 mutant of simian virus 40

Abstract

It was shown previously that mouse bone marrow cells transformed by simian virus 40 (SV40) show a reversible cell density-dependent phenotypic transition between the nonmacrophage (rapidly growing) and the macrophage (stationary) states; cells in low-density cultures are in the growing phase, express SV40 T antigen strongly as revealed by immunofluorescence, and lose typical macrophage properties such as immune phagocytosis; whereas cells in high-density cultures are in the stationary (nongrowing) phase, express SV40 T antigen weakly, and recover their macrophage properties (Takayama, 1980). In the hope of clarifying the relationship between T antigen, cell growth, and macrophage-specific cellular function, we examined the behavior at 33 and 39 degrees C of mouse bone marrow cells transformed by an SV40 gene A mutant (tsA640) whose mutation renders the molecular weight of 90K (large) T antigen temperature sensitive. The results presented in this paper suggest that functional large T antigen is required for cells in the stationary phase to initiate multiplication when transferred at lower density and is not necessary for a majority of them to maintain the nongrowing state (viability) at both high and lower cell densities, whereas it is required for cells in the growing phase to keep multiplying without losing their viability. The results also suggest that the functional large T antigen does not play a direct role in maintaining the cells as either phagocytic or nonphagocytic. It is also suggested that the physiological or tsA mutation-mediated arrest of growth may or may not be accompanied by induction and/or maintenance of cellular phagocytic activity depending on the culture state.

Cell growth and differentiation in vitro in mouse macrophages transformed by a tsA mutant of simian virus 40. II. Changes in the distribution of DNA content during the reversible transition between macrophage and nonmacrophage states in the cultures of tsA 640‐transformed macrophages

“…Cells lost their phagocytic ability as they resumed proliferation and became phagocytic again after their proliferation stopped at saturation density (3 x lo6 cells per 35-mm dish) (Fig. lB), as was reported in detail previously (Takayama, 1980;Tanigawa et al, 1983). Taking the mean DNA content of mouse peritoneal macrophages as 1 unit in the scale of fluorescence intensity in the flow cytogram, the cultures showed two distinct peaks-one located around the 1.0-unit position (peak 1.0) and the other around the 1.6-unit position (peak 1.61, and a plateau distribution continuing to 3.2 units.…”

Cell growth and differentiation in vitro in mouse macrophages transformed by a tsA mutant of simian virus 40. III. Large T antigen level and cell proliferation and survival in an SV40 tsA640‐transformed macrophage line

“…The A64O-transformed macrophages proliferating a t 33°C die when they are exposed to 39°C (Tanigawa et al, 1983). In this case, the amount of large T antigen per cell was not reduced to the level seen in the confluent cells when shifted to 39°C.…”

“…Although the number of cells in the culture remains constant at confluence at 33°C in both WT SV40-transformed and A64O-transformed macrophage lines (Tanigawa et al, 1983), the confluent culture of A640-BB-1 contained a considerable fraction of DNA-synthesizing cells. We assume that the confluent cells are not strictly quiescent but are slowly proliferating, with a balance of proliferation and death.…”

Alteration in cyclic adenosine 3′:5′‐monophosphate binding proteins during the phenotypic change of mouse macrophages transformed by a temperature‐sensitive mutant (tsA640) of SV40

“…[3H]TdR-labeled cells did not appear in the parallel cultures of tsA640-transformants that were incubated at 39.0"C for 5 days (data not shown) (Tanigawa et al, 1983).…”