Lnk family adaptor proteins in the development and regulation of immune-competent cells

Lnk、SH2-B和APS构成细胞内接头蛋白家族。APS-/-小鼠存活，可生育，无异常或生长迟缓。免疫方面，APS-/-小鼠除腹腔B-1细胞数量增加外，淋巴细胞和骨髓细胞发育和分布正常。与野生型细胞相比，BCR刺激后APS-/- b -1细胞的f -肌动蛋白含量降低。Lnk、SH2-B、APS均在肥大细胞中表达。我们从lnk^<-/->、SH2-B^<-/->和APS^<-/->小鼠中建立了骨髓源性肥大细胞（BMMCs）。在缺乏Lnk或SH2-B的情况下，bmmc的增殖和各项功能正常。相比之下，aps缺陷bmmc在交联FcεRI后表现出增强的脱颗粒。aps缺陷细胞在稳态下显示肌动蛋白组装减少。我们的研究结果提示APS在控制肌动蛋白细胞骨架和肥大细胞脱颗粒程度方面的潜在作用。虽然Lnk负性调节b淋巴生成和b淋巴生成，但Lnk介导的调节的分子机制尚不清楚。我们发现Lnk控制由受体酪氨酸激酶（RTKs）激活的肌动蛋白重组，从而调节细胞分裂和迁移。表达lnk的成纤维细胞表现出扁平、扩散的形态和突出的肌动蛋白聚合，由于细胞分裂受损导致多核细胞形成。Lnk与Rac、Vav、PAK和丝状蛋白A共免疫沉淀，提示在Lnk的支持下形成了细胞骨架调节蛋白复合物。因此，Lnk作为一种新的支架分子，将rtk与细胞骨架调节成分连接起来。骨髓中造血干细胞（hsc）的数量受发育调控。link -/-小鼠成年骨髓中功能性造血干细胞的数量增加了10倍以上。此外，克隆分析表明，部分缺乏link的造血干细胞是高度再生的干细胞，表现为更高程度的自我更新能力。少

Lnk, SH2-B and APS form an intracellular adaptor protein family. APS-/-mice were viable, fertile, and showed no abnormalities or growth retardation. Immunologically, APS-/-mice showed normal development and distribution of lymphocytes and myeloid cells, except for increased numbers of B-1 cell in the peritoneal cavity. F-actin contents after BCR stimulation was decreased in APS-/-B-1 cells compared to wild-type cells. Lnk, SH2-B, and APS are all expressed in mast cells. We established bone marrow-derived mast cells (BMMCs) from lnk^<-/->, SH2-B^<-/-> and APS^<-/-> mice. Proliferation and various function of BMMCs were normal in the absence of Lnk or SH2-B. In contrast, APS-deficient BMMCs showed augmented degranulation after cross-linking FcεRI. APS-deficient cells showed reduced actin assembly at steady state. Our results suggest potential roles of APS in controlling actin cytoskeleton and magnitude of degranulation in mast cells.While Lnk negatively regulates B-lymphopoiesis and earl … More y hematopoiesis, the molecular mechanism underlying Lnk-mediated regulation remains obscure. We found Lnk controls actin reorganization activated by receptor tyrosine kinases (RTKs), thereby regulating cell division and migration. Lnk-expressing fibroblasts showed flattened, spreading morphology and prominent actin polymerization that resulted in multinuclear cell formation due to impaired cytokinesis. Lnk was co-immunoprecipitated with Rac, Vav, PAK and filamin A, which suggested the formation of a cytoskeletal regulatory protein complex supported by Lnk. Thus, Lnk functions as a novel scaffold molecule that links RTKs with cytoskeletal regulatory components.The number of hematopoietic stem cells (HSCs) in the bone marrow is developmentally regulated. Lnk-/-mice display more than 10-fold increase of functional HSCs in number in the adult bone marrow. In addition, a clonal analysis suggests that a part of Lnk-deficient HSCs are highly repopulating stem cells, manifested by higher degree of self-renewal capacity. Less