Atreya P L, Barnes J, Katar M, Alcala J, Maisel H
Department of Anatomy and Cell Biology, Wayne State University, School of Medicine, Detroit, MI 48201.
Curr Eye Res. 1989 Sep;8(9):947-56.
N-cadherin was identified in the human lens by its immunological specificity, and concanavalin-A (Con-A) binding. The 135 kd glycoprotein was partially purified from human lens plasma membranes by Con-A affinity column chromatography. In the newborn lens, N-cadherin is distributed equally in amount between cortical and nuclear membranes. It is markedly decreased in the nuclear membranes of the 2 year-old lens and was no longer detectable in the nucleus of 15 yr-old and older lenses (15 yrs - 86 yrs). Such nuclear loss of N-cadherin is consistent with similar findings in the chicken and bovine lens. At all ages, N-cadherin was readily detected in cortical fiber-cells. When expressed as a ratio to MP26 content, the amount of N-cadherin of the total fiber mass declines at least 4-fold from newborn to 15 years of age, and remains stable thereafter. Homogenization of bovine lenses in the presence of Ca++ resulted in a marked loss of the protein, suggestive of degradation by a calcium-activated protease. The loss of N-cadherin with aging in fiber cells suggests either an alteration in the mode of membrane adhesion of these cells, or a decline in adhesiveness of nuclear as compared to cortical fiber-cells.
通过免疫特异性和伴刀豆球蛋白A（Con-A）结合，在人晶状体中鉴定出了N-钙黏蛋白。通过Con-A亲和柱色谱法从人晶状体质膜中部分纯化出了这种135 kd的糖蛋白。在新生儿晶状体中，N-钙黏蛋白在皮质膜和核膜中的分布量相等。在2岁晶状体的核膜中它明显减少，在15岁及以上（15岁至86岁）的晶状体核中则不再能检测到。N-钙黏蛋白的这种核内缺失与在鸡和牛晶状体中的类似发现一致。在所有年龄段，在皮质纤维细胞中都能很容易地检测到N-钙黏蛋白。当以与MP26含量的比值表示时，从新生儿到15岁，总纤维质量中N-钙黏蛋白的量至少下降4倍，此后保持稳定。在Ca++存在的情况下对牛晶状体进行匀浆处理导致该蛋白明显损失，提示被钙激活蛋白酶降解。纤维细胞中N-钙黏蛋白随年龄增长而丧失，这表明这些细胞的膜黏附模式发生了改变，或者与皮质纤维细胞相比，核的黏附性下降。
