Hernandez-Hansen Valerie, Smith Alexander J, Surviladze Zurab, Chigaev Alexandre, Mazel Tomas, Kalesnikoff Janet, Lowell Clifford A, Krystal Gerald, Sklar Larry A, Wilson Bridget S, Oliver Janet M
Department of Pathology and Cancer Research and Treatment Center, University of New Mexico School of Medicine, CRF 205, 2325 Camino De Salud, Albuquerque, NM 87131, USA.
J Immunol. 2004 Jul 1;173(1):100-12. doi: 10.4049/jimmunol.173.1.100.
Studies in B cells from Lyn-deficient mice have identified Lyn as both a kinetic accelerator and negative regulator of signaling through the BCR. The signaling properties of bone marrow-derived mast cells from Lyn(-/-) mice (Lyn(-/-) BMMCs) have also been explored, but their signaling phenotype remains controversial. We confirm that Lyn(-/-) BMMCs release more beta-hexosaminidase than wild-type BMMCs following FcepsilonRI cross-linking and show that multiple mast cell responses to FcepsilonRI cross-linking (the phosphorylation of receptor subunits and other proteins, the activation of phospholipase Cgamma isoforms, the mobilization of Ca(2+), the synthesis of phosphatidylinositol 3,4,5-trisphosphate, the activation of the alpha(4)beta(1) integrin, VLA-4) are slow to initiate in Lyn(-/-) BMMCs, but persist far longer than in wild-type cells. Mechanistic studies revealed increased basal as well as stimulated phosphorylation of the Src kinase, Fyn, in Lyn(-/-) BMMCs. Conversely, there was very little basal or stimulated tyrosine phosphorylation or activity of the inositol phosphatase, SHIP, in Lyn(-/-) BMMCs. We speculate that Fyn may substitute (inefficiently) for Lyn in signal initiation in Lyn(-/-) BMMCs. The loss of SHIP phosphorylation and activity very likely contributes to the increased levels of phosphatidylinositol 3,4,5-trisphosphate and the excess FcepsilonRI signaling in Lyn(-/-) BMMCs. The unexpected absence of the transient receptor potential channel, Trpc4, from Lyn(-/-) BMMCs may additionally contribute to their altered signaling properties.
对 Lyn 基因缺陷小鼠 B 细胞的研究已确定 Lyn 既是 B 细胞抗原受体（BCR）信号传导的动力学加速器，也是负调节因子。人们也对 Lyn(-/-)小鼠骨髓来源肥大细胞（Lyn(-/-) BMMCs）的信号传导特性进行了探索，但其信号表型仍存在争议。我们证实，在 FcepsilonRI 交联后，Lyn(-/-) BMMCs 比野生型 BMMCs 释放更多的β-己糖胺酶，并表明 Lyn(-/-) BMMCs 对 FcepsilonRI 交联的多种肥大细胞反应（受体亚基和其他蛋白质的磷酸化、磷脂酶 Cγ亚型的激活、Ca(2+)的动员、磷脂酰肌醇 3,4,5-三磷酸的合成、α(4)β(1)整合素 VLA-4 的激活）启动缓慢，但持续时间远比野生型细胞长。机制研究表明，Lyn(-/-) BMMCs 中 Src 激酶 Fyn 的基础磷酸化以及刺激后的磷酸化均增加。相反，Lyn(-/-) BMMCs 中肌醇磷酸酶 SHIP 的基础或刺激后的酪氨酸磷酸化及活性极低。我们推测，在 Lyn(-/-) BMMCs 的信号启动过程中，Fyn 可能（低效地）替代 Lyn 的功能。SHIP 磷酸化和活性的丧失很可能导致 Lyn(-/-) BMMCs 中磷脂酰肌醇 3,4,5-三磷酸水平升高以及 FcepsilonRI 信号传导过度。Lyn(-/-) BMMCs 意外缺失瞬时受体电位通道 Trpc4，这可能也导致了其信号特性的改变。
