| Co-Investigator(Kenkyū-buntansha) |
山内 保生 九州大学, 医学部, 医員
YAMAUCHI Yasuo Faculty of Medicine, Kyushu University, Resident
山内 保夫 九州大学, 医学部, 医員
久志本 孝一 九州大学, 医学部, 医員
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| Research Abstract |
To examine the mechanism of induction of differentiation in the human malignant T-lymphoblastic cell line, MOLT-3, by 12-o-tetradecanoylphorbol-13-acetate (TPA), the role of receptors for phorbol esters, the activation of protein kinase C (PKC) and of the Ca^<2+>- modilization was investigated. Binding of ^3H -phorbol-12,13- dibutyrate (PDB) to TPA-resistant subclones (R01-R05) derived from MOLT-3 was less than 50 % of that of the parental MOLT-3. Scatchard analysis showed that the concentration of phorbol ester receptors in a TPA-resistant subclone (R01) was about 50 % of that in the parental MOLT-3, but affinities of binding were similar, indicating that more than a certain number of phorbol ester receptors is required to induce differentiation by TPA in MOLT-3.
PKC activities were also assayed in MOLT-3 and its 5 subclones (R01-R05) resistant to TPA-induced cell differentiation. The cytosolic PKC activities of R01-R05 cells were 40-50 % of that of the parental MOLT-3. TPA treatment led to a rapid decrease in PKC activities in the cytosol, together with a concomitant increase in PKC activities in the particulate fraction, in both MOLT-3 and a TPA-resistant subclone, R01. Thus, translocation of PKC from the cytosol to the membrane occurred following TPA stimulation in both cell lines. However, the amount of PKC translocated from the cytosol to the particulate fraction in R01 was only 20 % of that of the parental MOLT-3. These findings suggest that the quantity of cytosolic PKC activity and the extent of translocation may relate to responses to TPA-induced cell differentiation in MOLT-3.
Ionomycin, which mobilizes cytoplsmic Ca^<2+>, when added together with TPA to MOLT-3, could enhance the induction effect of TPA in terms of cell proliferation, size and morphology. These results suggest that cytoplasmic mobilization of Ca^<2+> plays an assistant role in induction of differentiation in MOLT-3 cells.
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