Abstract：
The immunoglobulin superfamily represents a diverse set of cell-cell contact proteins and includes well-studied members such as NCAM1, DSCAM, L1 or the contactins which are strongly expressed in the nervous system. In this review we put our focus on the biological function of a less understood subgroup of Ig-like proteins composed of CAR (coxsackievirus and adenovirus receptor), CLMP (CAR-like membrane protein) and BT-IgSF (brain and testis specific immunoglobulin superfamily). The CAR-related proteins are type I transmembrane proteins containing an N-terminal variable (V-type) and a membrane proximal constant (C2-type) Ig domain in their extracellular region which are implicated in homotypic adhesion. They are highly expressed during embryonic development in a variety of tissues including the nervous system whereby in adult stages the protein level of CAR and CLMP decreases, only BT-IgSF expression increases within age. CAR-related proteins are concentrated at specialized cell-cell communication sites such as gap or tight junctions and are present at the plasma membrane in larger protein complexes. Considerable progress has been made on the molecular structure and interactions of CAR while research on CLMP and BT-IgSF is at an early stage. Studies on mouse mutants revealed biological functions of CAR in the heart and for CLMP in the gastrointestinal and urogenital systems. Furthermore, CAR and BT-IgSF appear to regulate synaptic function in the hippocampus.
摘要：
免疫球蛋白超家族代表一组不同的细胞-细胞接触蛋白，包括经过充分研究的成员，如NCAM1，DSCAM，L1或在神经系统中强烈表达的接触素。在这篇综述中，我们将重点放在由CAR（柯萨奇病毒和腺病毒受体）组成的Ig样蛋白亚组的生物学功能上，CLMP（CAR样膜蛋白）和BT-IgSF（脑和睾丸特异性免疫球蛋白超家族）。CAR相关蛋白是I型跨膜蛋白,其在其胞外区中含有N末端可变(V型)和膜近端恒定(C2型)Ig结构域,其与同型粘附有关。它们在胚胎发育过程中在包括神经系统在内的各种组织中高度表达，因此在成年阶段，CAR和CLMP的蛋白质水平降低。仅BT-IgSF表达在年龄内增加。CAR相关蛋白质集中在专门的细胞-细胞通讯位点，如间隙或紧密连接，并以更大的蛋白质复合物存在于质膜。CAR的分子结构和相互作用已经取得了相当大的进展，而CLMP和BT-IgSF的研究还处于早期阶段。对小鼠突变体的研究揭示了CAR在心脏中的生物学功能以及CLMP在胃肠道和泌尿生殖系统中的生物学功能。此外，CAR和BT-IgSF似乎调节海马的突触功能。
