Daws M R, Lanier L L, Seaman W E, Ryan J C
Department of Immunology, VA Medical Center San Francisco, San Francisco, USA.
Eur J Immunol. 2001 Mar;31(3):783-91. doi: 10.1002/1521-4141(200103)31:3<783::aid-immu783>3.0.co;2-u.
The presence of a negatively charged residue in the transmembrane domain of DAP12 precludes its cell surface expression in the absence of a partner receptor containing a positive charge in its transmembrane domain. We utilized this property of DAP12 to screen a BALB / c macrophage cDNA library for novel molecules that induce cell surface expression of DAP12. By this method, we cloned a cell surface receptor with a single Ig (V) domain, a transmembrane lysine residue, and a short cytoplasmic domain. By homology screening of BALB / c macrophage libraries, we identified a second cDNA for a highly homologous receptor. These receptors appear to be the mouse orthologues of a recently identified human cDNA, TREM-2, so we have designated the receptors as mouse TREM-2a and TREM-2b. By Northern blotting, transcripts for TREM-2 were found in each of three macrophage cell lines but not in a variety of other hematopoietic cell lines. We further demonstrate that TREM-2a is associated with endogenous DAP12 in macrophage cells, and cross-linking of TREM-2a on the surface of macrophages leads to the release of nitric oxide. Our studies define TREM-2 as a receptor family in mouse macrophages and demonstrate the capacity of these receptors to activate macrophage function through DAP12.
DAP12跨膜结构域中带负电荷的残基的存在，使得在没有跨膜结构域中带正电荷的伴侣受体的情况下，它无法在细胞表面表达。我们利用DAP12的这一特性，在BALB/c巨噬细胞cDNA文库中筛选能诱导DAP12在细胞表面表达的新分子。通过这种方法，我们克隆了一种细胞表面受体，它具有一个单一的Ig（V）结构域、一个跨膜赖氨酸残基和一个短的胞质结构域。通过对BALB/c巨噬细胞文库的同源性筛选，我们鉴定出了第二个高度同源受体的cDNA。这些受体似乎是最近鉴定出的人类cDNA TREM-2的小鼠直系同源物，因此我们将这些受体命名为小鼠TREM-2a和TREM-2b。通过Northern印迹法，在三种巨噬细胞系中的每一种中都发现了TREM-2的转录本，但在多种其他造血细胞系中未发现。我们进一步证明，TREM-2a在巨噬细胞中与内源性DAP12相关联，巨噬细胞表面的TREM-2a交联会导致一氧化氮的释放。我们的研究将TREM-2定义为小鼠巨噬细胞中的一个受体家族，并证明了这些受体通过DAP12激活巨噬细胞功能的能力。
