A NOVEL FUNCTION OF ENOLASE FROM RABBIT MUSCLE - AN IMMUNOGLOBULIN PRODUCTION STIMULATING FACTOR

Rabbit muscle enolase stimulates immunoglobulin production by a human hybridoma line, HB4C5 cells under serum-free condition. IgM productivi ty of HB4C5 cells was enhanced more than 20-fold by this enzyme at 220 mu g/ml. Human peripheral blood lymphocytes were also facilitated the ir IgM and IgG productivity in the serum-free medium. However, baker's yeast enolase was ineffective to accelerate immunoglobulin production by HB4C5 cells, in spite of the same specific enzymatic activity as r abbit muscle enolase. There were differences in sensitivities against heat treatment and trypsin digestion between IPSF and enzymatic activi ties of enolase. These results imply that the immunoglobulin productio n stimulating effect of rabbit muscle enolase is irrelevant to its enz ymatic function and reaction products. This fact also means that this enzyme has another function other than enzymatic one in glycolysis. Ra bbit muscle enolase enhanced IgM production of transcription-suppresse d HB4C5 cells treated with actinomycin D. Cycloheximide treatment of H B4C5 cells was useless to inhibit the expression of immunoglobulin pro duction stimulating activity. However, inhibition of post-transcriptio nal process by monensin invalidated the activity of enolase. These fin dings suggest that enolase from rabbit muscle accelerates the steps be tween translation and post-translational processes to enhance immunogl obulin productivity. In addition, laser confocal microscopic analysis revealed that enolase from rabbit muscle was subsequently incorporated by HB4C5 cells. (C) 1998 Elsevier Science B.V.