Rat basophilic leukaemia (RBL) cells overexpressing Rab3a have a reversible block in antigen-stimulated exocytosis.
Rat basophilic leukaemia (RBL) cells overexpressing Rab3a have a reversible block in antigen-stimulated exocytosis.
复制标题
过度表达 Rab3a 的大鼠嗜碱性白血病 (RBL) 细胞在抗原刺激的胞吐作用中具有可逆性阻断。
DOI：
10.1042/bj3230321
复制
发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Roberto Solari
中科院分区：
文献类型：
--
作者：
Janet Smith;Nicola Thompson;Jeff Thompson;John Armstrong;Brian Hayes;Andrew J. Crofts;Jane H. Squire;Carmel Teahan;Louise Upton;Roberto Solari
大鼠嗜碱性白血病（RBL）细胞系已被广泛用作研究肥大细胞分泌调节的方便模型系统。这些细胞通过IgE的高亲和力受体（Fcepsilon-RI）的活化导致脱粒和介体的细胞外释放。有很好的证据表明GTP酶在肥大细胞脱粒中的作用，并且许多来自Rab 3a效应结构域的肽的研究表明Rab 3a可能在该过程中起作用。然而，在神经内分泌细胞中，Rab 3a的过表达可作为受刺激的胞吐作用的负调节剂[Holz，Brondyk，Senter，Kuizon和Macara（1994）J.Biol.Chem.269，10229-10234; Johanes，Lledo，罗阿，Vincent，亨利和Darchen（1994）EMBO J.13，2029-2037]。为了研究Rab 3a在RBL脱粒中的功能，我们已经产生了稳定表达Rab 3a的RBL细胞的克隆，并表明在这些造血细胞中Rab 3a也可以作为胞吐的负调节剂发挥作用。Rab 3a的突变形式（Asn-135到Ile）的过表达，这是预测主要是GTP结合，也抑制脱粒。然而，过表达的突变形式的Rab 3a，在C-末端被截断，以消除网站的香叶基香叶基化未能抑制脱粒。Rab 3a的作用是特异性的分泌，我们没有观察到Rab 3a对受体介导的内吞作用的影响。Rab 3a诱导的脱粒阻滞可以通过用鸟苷5 '-[γ-硫代]三磷酸刺激链球菌溶血素-O-透化的细胞来绕过。我们从这些研究中得出结论，Rab 3a涉及颗粒靶向的早期阶段，而颗粒与质膜的融合受不同的下游GTP结合蛋白或蛋白质的调节。
The rat basophilic leukaemia (RBL) cell line has been widely used as a convenient model system to study regulated secretion in mast cells. Activation of these cells through the high-affinity receptor for IgE (Fcepsilon-RI) results in degranulation and the extracellular release of mediators. There is good evidence of a role for GTPases in mast cell degranulation, and a number of studies with peptides derived from the Rab3a effector domain have suggested that Rab3a may function in this process. However, in neuroendocrine cells, overexpression of Rab3a can act as a negative regulator of stimulated exocytosis [Holz, Brondyk, Senter, Kuizon and Macara (1994) J. Biol. Chem. 269, 10229-10234; Johanes, Lledo, Roa, Vincent, Henry and Darchen (1994) EMBO J. 13, 2029-2037]. In order to study the function of Rab3a in RBL degranulation, we have generated clones of RBL cells stably expressing Rab3a, and show that in these haematopoietic cells Rab3a can also function as a negative regulator of exocytosis. Overexpression of a mutant form of Rab3a (Asn-135 to Ile), which is predicted to be predominantly GTP-bound, also inhibited degranulation. However, overexpression of a mutant form of Rab3a that was truncated at the C-terminus to remove the sites for geranylgeranylation failed to inhibit degranulation. The effect of Rab3a is specific to secretion, and we observe no effect of Rab3a on receptor-mediated endocytosis. The Rab3a-induced block in degranulation can be bypassed by stimulation of streptolysin-O-permeabilized cells with guanosine 5'-[gamma-thio]triphosphate. We conclude from these studies that Rab3a is implicated in an early stage of granule targeting, whereas fusion of granules with the plasma membrane is regulated by a distinct downstream GTP-binding protein or proteins.