Involvement of the SgIGSF plasma membrane-spanning molecule in adhesion and survival of mast cells

SgIGSF（生精免疫球蛋白超家族）是最近发现的一种粘附分子，而小眼转录因子（MITF）在肥大细胞中表达是必不可少的。由于tg突变等位基因实际上是MITF基因的零突变，来自（WB x C57BL/6）F_1 (F_1)-tg/tg小鼠的培养肥大细胞（cmc）不表达SgIGSF，而来自F_1-野生型（+/+）小鼠的cmc则大量表达SgIGSF。当与NIH/3T3成纤维细胞共培养时，F_1-tg/tg cmc对NIH/3T3成纤维细胞粘附较差。腹腔注射骨髓源性肥大细胞（BMMCs）治疗急性细菌性腹膜炎有疗效。为了发挥这一作用，bmcs需要从腹膜腔沉淀肠系膜。采用肥大细胞缺陷小鼠F_1-W/W^ν [c-kit受体酪氨酸激酶（KIT）突变体]、F_1-Sl/Sl^d [KIT配体干细胞因子（SCF）突变体]和F_1-tg/tg检测BMMCs与肠系膜的相互作用。测量了三个参数：bmmc的数量(1)在腹腔注射肥大细胞缺陷小鼠5周后在肠系膜中出现的数量，(2)粘附在肠系膜间皮细胞上的数量，(3)在两种细胞共培养3和18小时时跨肠系膜间皮细胞单层迁移的数量。腹腔注射F_1-tg/tg cmc时，F_1-tg/tg cmc在肥大细胞缺陷F_1-W/W^ν小鼠腹腔内存活较差。通过逆转录病毒转染和转基因表达，SgIGSF在tg/tg cmc中异位表达。与对照组F_1-tg/tg CMCs相比，tg/tg CMCs不仅与NIH/3T3成纤维细胞具有更好的粘附性，而且在腹腔内的存活率更高。这些结果表明，SgIGSF在肥大细胞的粘附和存活中发挥了重要作用，SgIGSF和KIT在跨肠系膜间皮细胞的迁移中具有不同的作用。

SgIGSF (Spermatogenic Immunoglobulin Superfamily) is a recently identified adhesion molecule, and the microphthalmia transcription factor (MITF) was essential for its expression in mast cells. Since the tg mutant allele is practically a null mutation of the MITF gene, cultured mast cells (CMCs) derived from (WB x C57BL/6)F_1 (F_1)-tg/tg mice did not express SgIGSF whereas CMCs from F_1-wild-type (+/+) mice expressed it abundantly. When cocultured with NIH/3T3 fibroblasts, F_1-tg/tg CMCs showed poor adhesion to NIH/3T3 fibroblasts.Intraperitoneal injection of bone marrow-derived mast cells (BMMCs) has therapeutic efficacy against acute bacterial peritonitis. For this role, BMMCs need to settle down the mesentery from the peritoneal cavity. Interaction between BMMCs and the mesentery was examined by using mast cell deficient F_1-W/W^ν [c-kit receptor tyrosine kinase (KIT) mutant], F_1-Sl/Sl^d [KIT ligand stem cell factor (SCF) mutant] and F_1-tg/tg mice. Three parameters were measured : the number of BMMCs (1) developed in the mesentery 5 weeks after intraperitoneal injection into mast cell deficient mice, (2) adhered to mesenteric mesothelial cells, and (3) transmigrated across the mesenteric mesothelial cell monolayer when coculturing both cells for 3 and 18 hours, respectively. When injected intraperitoneally, F_1-tg/tg CMCs showed poor survival in the peritoneal cavity of mast cell-deficient F_1-W/W^ν mice. SgIGSF was expressed in tg/tg CMCs ectopically through retroviral transfection and through expression of a transgene. The resulting tg/tg CMCs showed not only a better adhesion to NIH/3T3 fibroblasts but also a better survival in the peritoneal cavity than control F_1-tg/tg CMCs.These results showed that SgIGSF played a significant role in mast-cell adhesion and survival, and that SgIGSF and KIT had distinct roles in transmigration across mesenteric mesothelial cells.