Baeker T R, Simons E R, Rothstein T L
J Immunol. 1987 Apr 15;138(8):2691-7.
Cytochalasin promotes the progression of anti-immunoglobulin-treated B lymphocytes to S phase. However, the intracellular events induced by cytochalasin which may mediate signaling for progression have not been elucidated. In this study, the effect of cytochalasin on the level of intracellular free calcium in murine splenic B lymphocytes was assessed by using the fluorescent calcium indicator Indo-1. Cytochalasins A, B, D, and E induced a rapid and sustained elevation of intracellular free calcium. The calcium response to cytochalasin derived largely from the influx of extracellular calcium, although a small, transient elevation in intracellular calcium persisted when the suspension medium was made calcium-free with EGTA, implicating an intracellular source for a portion of the calcium response. Single cell fluorescence studies revealed that cytochalasin elicited a calcium response in most splenic B cells in suspension, indicating that this phenomenon is not restricted to a subpopulation of responding B cells. Phorbol esters inhibited the B cell calcium response to cytochalasin, and an established response to cytochalasin was rapidly and completely reversed by subsequently administered phorbol ester. T cells that lack the cytochalasin pathway showed a markedly diminished calcium response that was only apparent at higher cytochalasin concentration. However, B cells from xid-defective [CBA/N X DBA/2]F1 males, which fail to respond to anti-immunoglobulin plus cytochalasin, showed a calcium response to cytochalasin similar to that of phenotypically normal F1 females. These data, along with the finding that the rise in intracellular calcium occurred in naive B cells as well as B cells previously treated with anti-immunoglobulin, suggest that there is no clear association between the calcium response induced by cytochalasin and the ability of cytochalasin to stimulate progression to S phase. However, this effect of cytochalasin may suggest a connection between actin filaments and calcium influx in B cells.
细胞松弛素可促进经抗免疫球蛋白处理的B淋巴细胞进入S期。然而，细胞松弛素诱导的可能介导细胞周期进程信号的细胞内事件尚未阐明。在本研究中，通过使用荧光钙指示剂Indo-1评估细胞松弛素对小鼠脾B淋巴细胞细胞内游离钙水平的影响。细胞松弛素A、B、D和E可诱导细胞内游离钙快速且持续升高。细胞松弛素引起的钙反应主要源于细胞外钙的内流，尽管当用乙二醇双四乙酸（EGTA）使悬浮培养基无钙时，细胞内钙仍有一小段短暂升高，这表明部分钙反应存在细胞内来源。单细胞荧光研究表明，细胞松弛素可使大多数悬浮的脾B细胞产生钙反应，这表明该现象并不局限于有反应的B细胞亚群。佛波酯可抑制B细胞对细胞松弛素的钙反应，并且预先建立的对细胞松弛素的反应可被随后加入的佛波酯迅速且完全逆转。缺乏细胞松弛素途径的T细胞显示出明显减弱的钙反应，且仅在较高细胞松弛素浓度时才明显。然而，来自xid缺陷型[CBA/N×DBA/2]F1雄性小鼠的B细胞，对抗免疫球蛋白加细胞松弛素无反应，但对细胞松弛素的钙反应与表型正常的F1雌性小鼠相似。这些数据，连同在未致敏B细胞以及先前用抗免疫球蛋白处理过的B细胞中均出现细胞内钙升高这一发现，表明细胞松弛素诱导的钙反应与细胞松弛素刺激进入S期的能力之间没有明确关联。然而，细胞松弛素的这种作用可能提示肌动蛋白丝与B细胞中的钙内流之间存在联系。
