Immunoquantitation of 80 kDa diacylglycerol kinase in pig and human lymphocytes and several other cells

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Abstract
80 kDa diacylglycerol kinase (DGK) was immunoquantitated in cell homogenates and subcellular fractions. It was extremely abundant in the cytosol of various lymphocytes and comprised, in the highest case, more than 0.2% of the total soluble protein in T cell-enriched pig splenocytes. The lymphocyte membrane contained less than 10% of the total cellular DGK protein. The content of 80 kDa DGK in the human T cell leukemic cell line, Jurkat (360 ng/mg homogenate protein), was similar to those in pig and human peripheral blood lymphocytes. In contrast, the enzyme level was very low in the human promyeloblastic cell line, HL-60 (< 10 ng/mg homogenate protein), and was undetectable in human polymorphonuclear leukocytes. These findings indicate that the content of 80 kDa DGK is markedly variable depending on the type of cells, even though all these cells are known to accumulate phosphatidate rapidly upon cell stimulation.