Similar molecular properties of granulocyte-macrophage colony-stimulating factors produced by different mouse organs in vitro and in vivo.

Abstract

Granulocyte-macrophage colony-stimulating factor (GM-CSF) was partially purified from post-endotoxin serum and conditioned media produced by organs from both normal and endotoxin-injected C57BL mice. The organs used to condition medium were heart, thigh muscle, salivary gland, thymus, spleen, kidney, brain, and femur shaft. The charge properties, molecular weights, and concanavalin A binding profiles of these GM-CSFs were analyzed and compared to purified mouse lung GM-CSF. All the GM-CSFs examined were shown to be gycoproteins since a proportion of the activity (80 to 100%) bound to concanavalin A-Sepharose. The organ-conditioned medium GM-CSFs were purified (3- to 13-fold) by absorption to calcium phosphate gel and chromatography on DEAE-Sepharose (further 2- to 10-fold). Analysis of the DEAE-Sepharose elution profiles indicated that there were two major charge species of GM-CSF eluting at conductivities of 10 and 14 mmho. These partially purified GM-CSFs showed considerable differences in their apparent molecular weights on Sephacryl S-200 (37,000 to 200,000). However, these differences could be eliminated by treating the GM-CSFs with neuraminidase and performing molecular sizing experiments under dissociating conditions (Sepharose CL-6B, 6 M guanidine hydrochloride). Although some of the GM-CSFs showed anomalously high molecular weights (40,000) on gel filtration columns, even under dissociating conditions, this appeared to be due to properties of the sialic acid residues. After neuraminidase treatment all of the conditioned medium GM-CSFs eluted from DEAE-Sepharose as a single peak of biological activity at a conductivity of 10 mmho and from gel filtration columns in the presence of 6 M guanidine hydrochloride as a single molecular weight species of approximately 23,000. GM-CSF from post-endotoxin serum (produced in vivo) eluted from the gel filtration column with an apparent molecular weight of 39,000, but analysis using polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate indicated that this GM-CSF also had an apparent molecular weight of 23,000.