Intracellular translocation of phosphatidate phosphatase in maturing safflower seeds: a possible mechanism of feedforward control of triacylglycerol synthesis by fatty acids.

Phosphatidate phosphatase activity was found both in the cytosol and in the microsomal membrane of maturing safflower seeds. The combined and relative activities of these two forms varied with seed maturation. During the period of rapid triacylglycerol accumulation in the cell, most of the phosphatidate phosphatase activity was membrane-bound; at the initial and last stages of seed development when triacylglycerol synthesis was at an insignificant level, the majority of the activity was soluble. The potassium salts of palmitic, stearic and oleic acids, which are the fatty acid products of proplastids, caused the translocation of the cytosolic phosphatidate phosphatase to the microsomal membrane, while laurate and linoleate, which are not products of proplastids, showed no effect. Oleoyl-CoA did not convert the soluble form of the enzyme into the membrane-bound form. The translocation induced by oleate was reversible. The cytosolic phosphatidate phosphatase of safflower seeds was not transferred to the microsomal membranes prepared from soybean, a plant species of Leguminosae, and from rapeseed, a species of Cruciferae, but was transferred to that from sunflower, which belongs to the same family as safflower, Compositae. These observations suggest that in maturing oil seeds the rate of fatty acid synthesis in proplastids may regulate the species-specific translocation of phosphatidate phosphatase between the cytosol and the endoplasmic reticulum membrane where triacylglycerol synthesis occurs and that in turn the translocation of this ambiquitous enzyme could control the rate of triacylglycerol synthesis in the cell.

Interleukin 2 defect in the peripheral blood and the lung in patients with Sjögren's syndrome.

We studied interleukin 2 (IL-2) production both in the peripheral blood and the lung in patients with Sjögren's syndrome (SS). IL-2 production of the peripheral blood mononuclear cells (PBMC) was significantly impaired in patients with SS (P less than 0.001). The patients with extraglandular disease and with associated connective tissue disease were more defective in IL-2 production. The defect could not be attributable to culture conditions. Both OKT4+ and OKT8+ T cells were deficient in producing IL-2. However, impaired IL-2 production could be partly restored by either (1) adding PMA to the PHA-stimulated culture, or (2) supplementing indomethacin (IM) from the initiation of the culture, or (3) depletion of adherent cells from PBMC. Furthermore, SS T cells were more sensitive to PGE1 than normal controls. In contrast, the response of PBMC to IL-2 was not disturbed in SS. IL-1 production of SS PBMC was not defective although there seemed to be suppressive factor(s) produced by SS adherent cells. In addition, IL-2 production of SS pulmonary lymphocytes was also decreased, suggesting that IL-2 producing cells might not be sequestrated in the lung. These data suggest that qualitative T cell defects and suppressor macrophages might be responsible for defective IL-2 production in SS and that IL-2 deficiency may contribute to the disordered immunoregulation in SS.