Lensch Martin, Lohr Michaela, Russwurm Roland, Vidal Michel, Kaltner Herbert, André Sabine, Gabius Hans-Joachim
Institute for Physiological Chemistry, Faculty of Veterinary Medicine, Ludwig-Maximilians-University Munich, Veterinärstr. 13, D-80539 Munich, Germany.
Int J Biochem Cell Biol. 2006;38(10):1741-58. doi: 10.1016/j.biocel.2006.04.004. Epub 2006 Apr 28.
Presence of species-specific gene divergence in a protein family prompts to thoroughly study structural aspects and expression profiles of the products. We herein focus on two members of an adhesion/growth-regulatory group of endogenous lectins, i.e. galectins-5 and -9. After first ascertaining species specificity of occurrence of galectin-5, constituted by a short section of rat galectin-9's N-terminal part and its C-terminal carbohydrate recognition domain, by database mining, we next detected and defined sequence differences in the proximal promoter region between the two genes. The ensuing hypothesis for distinct expression profiles was tested first by RT-PCR and then by immunohistochemistry. For the latter purpose, we employed antibodies rigorously controlled for absence of cross-reactivity including assays with various other galectins and, if necessary, refined by chromatographic removal of bi- or oligospecific activities. Indeed, the galectins have non-identical expression profiles, qualitative differences, e.g. seen for galectin-5-positive bone marrow and erythrocytes or for hitherto unknown expression in cells of the theca folliculi and galectin-9-positive skin epidermis and esophageal epithelium. Lack of hepatocyte or renal cortex staining separates these two expression profiles in rat from localization of galectin-9 in mouse. Interspecies extrapolation in a case of a galectin involved in unique gene divergence may thus not be valid. The presented results on galectin-5 relative to galectin-9 intimate distinct functions especially in erythropoiesis and imply currently unknown mechanisms to compensate its absence from the galectin network in other mammals.
蛋白质家族中物种特异性基因差异的存在促使人们深入研究其产物的结构特征和表达谱。我们在此聚焦于内源性凝集素粘附/生长调节组中的两个成员，即半乳糖凝集素-5和-9。通过数据库挖掘首先确定了由大鼠半乳糖凝集素-9的N端短片段及其C端碳水化合物识别结构域构成的半乳糖凝集素-5的物种特异性后，我们接下来检测并确定了这两个基因近端启动子区域的序列差异。随后，关于不同表达谱的假设首先通过逆转录聚合酶链反应（RT-PCR）进行检验，然后通过免疫组织化学进行检验。为了实现后者的目的，我们使用了经过严格控制以确保无交叉反应性的抗体，包括与各种其他半乳糖凝集素的检测，如有必要，还通过色谱法去除双特异性或寡特异性活性进行了优化。事实上，这两种半乳糖凝集素具有不同的表达谱，存在定性差异，例如在半乳糖凝集素-5阳性的骨髓和红细胞中，或者在卵泡膜细胞中迄今未知的表达，以及半乳糖凝集素-9阳性的皮肤表皮和食管上皮中。大鼠肝细胞或肾皮质无染色将这两种表达谱与小鼠中半乳糖凝集素-9的定位区分开来。因此，在涉及独特基因差异的半乳糖凝集素的情况下，种间推断可能无效。所呈现的关于半乳糖凝集素-5相对于半乳糖凝集素-9的结果表明它们具有不同的功能，尤其是在红细胞生成方面，并暗示了目前未知的机制来补偿其在其他哺乳动物半乳糖凝集素网络中的缺失。
