Characterization of the transport system of prostaglandin A2 in L-1210 murine leukemia cells.

Prostaglandin (PG) A2 has been shown to be actively incorporated into mammalian cells and transferred to the cell nucleus. To characterize the properties of the PGA2 transfer system, we examined the status of PGA2 in L-1210 cells with modified cellular glutathione (GSH) levels. PGA2 in the cytosol fraction of the cells existed in its free-form, the GSH conjugate-form and a macromolecule associate-form (protein bound-form). When the GSH level was lowered under culture conditions, the amount of free-form increased while that of the protein bound-form was unchanged. When PGA2-loaded cells were incubated in a salt solution, free- and conjugate-forms were emitted from the cells. A concomitant decrease and increase of protein bound PGA2 in cytosol and nuclei, respectively, were observed. Subsequent studies with isolated cellular fractions revealed that PGA2 bound to cytosolic protein was transported into the nuclear interior in a temperature-dependent manner. The binding of PGA2 to the protein and subsequent transport to the nuclei were inhibited by PGJ2 and 4-hydroxy-cyclopentenone, but not by PGB2, PGD2, PGE2, PGF2 alpha, arachidonic acid or oleic acid. N-Ethylmaleimide (NEM) and p-chloromercuribenzoate (PCMB) strongly interfered with these transfer processes, suggesting that sulfhydryl components are involved in the transport of PGA2. Subfractionation of cytosol by gel chromatography proved the presence of two proteins (100-150 kDa and 25-35 kDa) that are capable of transporting PGA2 to cell nuclei. Though 40-45 kDa proteins, which correspond to GSH S-transferases, bound to PGA2, they lacked the nuclear transport activities.