Smalheiser N R, Collins B J
Department of Pediatrics, University of Chicago, IL 60637.
Brain Res Dev Brain Res. 1992 Oct 23;69(2):215-23. doi: 10.1016/0165-3806(92)90162-p.
Cranin, a prominent 120 kDa laminin-binding protein of cell membranes, was originally identified and characterized by virtue of its ability to bind laminin directly in ligand-blotting assays. We have now raised polyclonal ('3070') and monoclonal antibodies (MAbs 4 and 199) against a partially purified preparation of cranin, and have characterized the properties and expression of the corresponding antigens in further detail. In immunoblots of E14 chick brain membranes, these antibodies all recognized a single major band migrating at approximately 125 kDa, with minor bands at 115 kDa and 170/180 kDa. The major 125 kDa antigen bound to laminin affinity beads in a divalent cation- and conformation-dependent manner. The 125 and 115 kDa bands were also the most prominent HNK-1 positive proteins detected overall within E14 chick brain membranes. MAbs 4 and 199 specifically inhibited the attachment of NG108-15 cells to low, but not high amounts of substratum-bound laminin. While the relation of 3070/MAb 4 antigens to cranin requires further elucidation, these data, together with evidence presented in the companion papers and elsewhere, suggest that the antigens are important in neural development by mediating at least some of the responses of neural cells to laminin--for example, by acting as a laminin receptor guiding axonal outgrowth and neuronal migration, or by involvement in the transport and binding of laminin to the surface of neurons and reactive glial cells that synthesize laminin.
Cranin是一种突出的120 kDa细胞膜层粘连蛋白结合蛋白，最初是通过其在配体印迹分析中直接结合层粘连蛋白的能力而被鉴定和表征的。我们现已制备了针对部分纯化的Cranin制剂的多克隆抗体（“3070”）和单克隆抗体（单克隆抗体4和199），并进一步详细表征了相应抗原的特性和表达。在E14鸡脑膜的免疫印迹中，这些抗体均识别出一条迁移在约125 kDa的单一主要条带，以及115 kDa和170/180 kDa的次要条带。主要的125 kDa抗原以二价阳离子和构象依赖性方式与层粘连蛋白亲和珠结合。125 kDa和115 kDa条带也是在E14鸡脑膜中总体检测到的最突出的HNK-1阳性蛋白。单克隆抗体4和199特异性抑制NG108-15细胞与少量但非大量底物结合的层粘连蛋白的附着。虽然3070/单克隆抗体4抗原与Cranin的关系需要进一步阐明，但这些数据，连同在配套论文和其他地方提供的证据表明，这些抗原在神经发育中很重要，至少通过介导神经细胞对层粘连蛋白的一些反应——例如，通过作为引导轴突生长和神经元迁移的层粘连蛋白受体，或通过参与层粘连蛋白向合成层粘连蛋白的神经元和反应性胶质细胞表面的运输和结合。
