Yan H C, Pilewski J M, Zhang Q, DeLisser H M, Romer L, Albelda S M
Department of Medicine, University of Pennsylvania Medical Center, Philadelphia 19104, USA.
Cell Adhes Commun. 1995 Feb;3(1):45-66. doi: 10.3109/15419069509081277.
PECAM-1, a cell adhesion molecule of the immunoglobulin gene (Ig) superfamily, has been implicated in white cell transmigration, integrin activation on lymphocytes, and cell-cell adhesion. The purpose of this investigation was to identify specific regions of the PECAM-1 extracellular domain mediating these functions by identifying the location of epitopes of bioactive anti-PECAM-1 monoclonal antibodies. The binding regions of mAbs important in PECAM-1-mediated leukocyte transmigration (Hec 7.2 and 3D2) were mapped to N-terminal Ig-like domains. The epitopes of monoclonal antibodies that activated integrin function on lymphocytes were dispersed over the entire extracellular region, but those that had the strongest activating effect were preferentially localized to the N-terminus of the molecule. The binding regions of mAbs that blocked PECAM-1-mediated heterophilic L-cell aggregation were located either in Ig-like domain 2 (NIH31.4) or Ig-like domain 6 (4G6 and 1.2). Site-directed mutagenesis further pinpointed the epitope of the 4G6 mAb to a hexapeptide, CAVNEG, within Ig-like domain 6. These results demonstrate that PECAM-1 contains multiple functional domains. Regions within N-terminal Ig-like domains appear to be required for transmigration. In contrast, two distinct regions were implicated in L-cell mediated heterophilic aggregation.
血小板内皮细胞黏附分子-1（PECAM-1）是免疫球蛋白基因（Ig）超家族的一种细胞黏附分子，与白细胞迁移、淋巴细胞上整合素的激活以及细胞间黏附有关。本研究的目的是通过确定具有生物活性的抗PECAM-1单克隆抗体表位的位置，来识别PECAM-1胞外域介导这些功能的特定区域。对在PECAM-1介导的白细胞迁移中起重要作用的单克隆抗体（Hec 7.2和3D2）的结合区域进行定位，发现其位于N端免疫球蛋白样结构域。激活淋巴细胞上整合素功能的单克隆抗体的表位分散在整个胞外区域，但激活作用最强的表位优先定位于该分子的N端。阻断PECAM-1介导的嗜异性L细胞聚集的单克隆抗体的结合区域位于免疫球蛋白样结构域2（NIH31.4）或免疫球蛋白样结构域6（4G6和1.2）。定点诱变进一步将4G6单克隆抗体的表位精确定位于免疫球蛋白样结构域6内的一个六肽CAVNEG。这些结果表明，PECAM-1包含多个功能结构域。N端免疫球蛋白样结构域内的区域似乎是迁移所必需的。相比之下，两个不同的区域与L细胞介导的嗜异性聚集有关。
