Role of pertussis toxin subunits in the cell-adhesion and signal-transduction in mice

百日咳毒素由5种不同的亚基（S1-S5）组成，在内分泌、免疫和神经系统中诱导多种独特的生物活性。百日咳毒素（PT）的亚基结构已明确，但各亚基在病理生理活动中的作用尚不清楚。虽然B寡聚物（S2-S5）被认为是一种结合蛋白，但B寡聚物中的每个亚基必须发挥相当复杂的作用，才能产生各种独特的PT活性。本研究探讨了PT各亚基作为黏附素和信号换能器在促进白细胞增多和脑病诱导中的作用。为此，在实验中，针对PT各亚基的小鼠单克隆抗体被用作主要的有力工具。静脉注射PT引起的白细胞增多在静脉注射后3天不仅可以被抗s1抗体和抗b单克隆抗体抑制，而且还可以被抗b单克隆抗体抑制。这一结果表明，受体细胞上的PT在白血病发生后仍然能够与抗体相互作用，并且外周血中不归巢的白细胞可能能够通过PT与抗体的中和而归巢。体外注射经PT处理的淋巴细胞也获得了类似的结果。为研究小鼠淋巴细胞与内皮细胞在体内和体外的相互作用，积累了一些初步的实验数据。此外，脑内注射PT引起的脑病和白细胞增多症也能被静脉注射的抗体所中和，但一些抗s1或抗s2抗体不能中和白细胞增多症，从而抑制了脑病的诱导。S2和S3似乎通过对细胞受体的粘附起着不同的特异性作用。S4可能有助于细胞膜信号转导的稳定，并在结合步骤和/或之后将S1的活性部分转移到活性位点。少

Pertussis toxin consisting of five different subunits (S1-S5) induces diverse and unique biological activities in endocrine, immune, and nervous systems. The subunit structure of pertussis toxin (PT) is well defined, but a role of each subunit in the pathophysiological activities is still unclear. The ADP-ribosyl-transferase activity of the S1 to G-protein is essential for most of major biological or toxic activities of PT.Although the B oligomer (S2-S5) is known as a binding protein, the each subunit in the B oligomer must play rather complex roles to produce the various unique PT activities.In this study, roles of each subunit of PT as adhesin and signal transducer in leukocytosis promotion and encephalopathy induction were explored. For this purpose, the mouse monoclonal antibodies against each subunit of PT were utilized as a major powerful tool through the experiments. Leukocytosis caused by intravenous (iv) injection of PT was suppressed by administration of not only anti-S1 but … More also anti-B monoclonal antibodies even at three days after the iv injections. This results suggest that PT on acceptor cells is still able to interact with the antibody after the time when the leukocytosis already occurred and that unhoming leukocytes in the peripheral blood may be able to home by the PT-neutralization with the antibody. Similar results were obtained by the iv injection of lymphocytes treated with PT in vitro. Some preliminary experimental data are accumulating to investigate the interaction between the lymphocytes and endothelial cells of mice in vivo and in vitro. Further, encephalopathy and leukocytosis induced by the intracerebral (ic) injection of PT in mice were also neutralized with the antibody administered by iv injection, but some anti-S1 or anti-S2 antibodies which were not able to neutralize the leukocytosis inhibited the induction of the encephalopathy. The S2 and S3 seems to play different and specific role through adherence to cell receptors. And S4 may contribute to stabilization of some signal transduction to the cell membrane and translocation of active part of S1 to an active site at and/or after the binding step. Less