Department of Immunology, Division of Biomedical Sciences, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Biochem Biophys Res Commun. 2012 Jan 6;417(1):646-50. doi: 10.1016/j.bbrc.2011.12.025. Epub 2011 Dec 11.
CD300a is a member of CD300 family molecules consisting of seven genes on human chromosome 17 and nine genes in mouse chromosome 11. CD300a has a long cytoplasmic region containing the consensus immunoreceptor tyrosine-based inhibitory motif (ITIM) sequence. Upon crosslinking with antibodies against CD300a, CD300a mediates an inhibitory signal in myeloid cells. However, the ligand for CD300a has not been identified and the physiological role of CD300a remained unclear. Here, we demonstrate that the chimeric fusion protein of CD300a extracellular domain with the Fc portion of human IgG specifically bound phosphatidylserine (PS), which is exposed on the outer leaflet of the plasma membrane of apoptotic cells. PS binding to CD300a induced SHP-1 recruitment by CD300a in mast cells in response to LPS. These results indicated that CD300a is a new PS receptor.
CD300a 是 CD300 家族分子的一员，该家族由人类染色体 17 上的 7 个基因和小鼠染色体 11 上的 9 个基因组成。CD300a 具有一个包含共识免疫受体酪氨酸抑制基序 (ITIM) 序列的长胞质区。与针对 CD300a 的抗体交联后，CD300a 在髓样细胞中传递抑制信号。然而，尚未鉴定出 CD300a 的配体，其生理作用仍不清楚。在这里，我们证明了 CD300a 细胞外结构域与人类 IgG 的 Fc 部分的嵌合融合蛋白特异性结合磷脂酰丝氨酸 (PS)，PS 暴露在凋亡细胞质膜的外叶。PS 与 CD300a 的结合诱导 LPS 刺激下肥大细胞中 CD300a 募集 SHP-1。这些结果表明 CD300a 是一种新的 PS 受体。
