Ina Y, Koide Y, Nezu N, Yoshida T O
J Immunol. 1987 Sep 1;139(5):1711-7.
The cross-linking of Fc receptors (FcR) on HL-60 cells inhibited the ability of recombinant IFN-gamma to induce HLA class II antigens. This appeared to be correlated with intracellular mRNA level. HL-60 lacked detectable HLA class II mRNA. IFN-gamma led to appearance of these transcripts, which were canceled by the cross-linking of FcR. Therefore, experiments were designed to investigate the intracellular signaling molecules regulating the appearance of HLA class II molecules or transcripts. The expression of HLA class II antigen induced by IFN-gamma was blocked by a calmodulin antagonist, W-7, but not by a protein kinase C (PKC) inhibitor, H-7. Furthermore, a direct activator of PKC, phorbol myristate acetate, was not able to induce the HLA class II antigen expression. These results suggest that IFN-gamma induces HLA class II antigens on HL-60 cells via a calcium-calmodulin pathway and not via a PKC pathway. Calmodulin is activated by a transient rise in the cytosolic free calcium. In fact, the measurement of calcium influx into HL-60 cells showed that a remarkable and time-dependent calcium accumulation was caused by IFN-gamma, and that depletion of Ca2+ from culture medium resulted in failure of IFN-gamma to induce class II antigen expression. Furthermore, calcium ionophore, A23187, by itself induced HLA class II antigen expression. These results suggest that IFN-gamma stimulates calcium influx and activates the calmodulin branch of the calcium messenger system, resulting in the induction of class II antigen expression on HL-60 cells. On the other hand, cross-linking of FcR elicited the accumulation of intracellular cAMP, which appeared to suppress the IFN-gamma-induced calcium influx, resulting in annulling HLA class II antigen-inducing activity of IFN-gamma. These intracellular events of HL-60 regulate the expression of HLA class II transcripts and molecules.
HL-60细胞上Fc受体（FcR）的交联抑制了重组干扰素-γ诱导HLA II类抗原的能力。这似乎与细胞内mRNA水平相关。HL-60缺乏可检测到的HLA II类mRNA。干扰素-γ导致这些转录本出现，而FcR的交联可使其消失。因此，设计实验来研究调节HLA II类分子或转录本出现的细胞内信号分子。干扰素-γ诱导的HLA II类抗原表达被钙调蛋白拮抗剂W-7阻断，但未被蛋白激酶C（PKC）抑制剂H-7阻断。此外，PKC的直接激活剂佛波醇肉豆蔻酸酯乙酸盐不能诱导HLA II类抗原表达。这些结果表明，干扰素-γ通过钙-钙调蛋白途径而非PKC途径诱导HL-60细胞上的HLA II类抗原。钙调蛋白由胞质游离钙的短暂升高激活。事实上，对HL-60细胞钙内流的测量表明，干扰素-γ引起显著的、时间依赖性的钙积累，并且培养基中Ca2+的耗尽导致干扰素-γ无法诱导II类抗原表达。此外，钙离子载体A23187自身可诱导HLA II类抗原表达。这些结果表明，干扰素-γ刺激钙内流并激活钙信使系统的钙调蛋白分支，从而导致HL-60细胞上II类抗原表达的诱导。另一方面，FcR的交联引起细胞内cAMP积累，这似乎抑制了干扰素-γ诱导的钙内流，导致干扰素-γ的HLA II类抗原诱导活性丧失。HL-60细胞的这些细胞内事件调节HLA II类转录本和分子的表达。
