Gonen T, Grey A C, Jacobs M D, Donaldson P J, Kistler J
School of Biological Sciences, University of Auckland, Auckland, New Zealand.
BMC Cell Biol. 2001;2:17. doi: 10.1186/1471-2121-2-17. Epub 2001 Aug 14.
Although MP20 is the second most highly expressed membrane protein in the lens its function remains an enigma. Putative functions for MP20 have recently been inferred from its assignment to the tetraspanin superfamily of integral membrane proteins. Members of this family have been shown to be involved in cellular proliferation, differentiation, migration, and adhesion. In this study, we show that MP20 associates with galectin-3, a known adhesion modulator.
MP20 and galectin-3 co-localized in selected areas of the lens fiber cell plasma membrane. Individually, these proteins purified with apparent molecular masses of 60 kDa and 22 kDa, respectively. A 104 kDa complex was formed in vitro upon mixing the purified proteins. A 102 kDa complex of MP20 and galectin-3 could also be isolated from detergent-solubilized native fiber cell membranes. Binding between MP20 and galectin-3 was disrupted by lactose suggesting the lectin site was involved in the interaction.
MP20 adds to a growing list of ligands of galectin-3 and appears to be the first representative of the tetraspanin superfamily identified to possess this specificity.
尽管MP20是晶状体中第二高表达的膜蛋白，但其功能仍是个谜。最近，通过将MP20归类于跨膜4超家族的整合膜蛋白，推测出其可能的功能。该家族成员已被证明参与细胞增殖、分化、迁移和黏附。在本研究中，我们发现MP20与已知的黏附调节剂半乳糖凝集素-3相关联。
MP20和半乳糖凝集素-3在晶状体纤维细胞质膜的特定区域共定位。单独来看，这些蛋白质纯化后的表观分子量分别为60 kDa和22 kDa。将纯化后的蛋白质混合后，在体外形成了一个104 kDa的复合物。MP20和半乳糖凝集素-3的102 kDa复合物也可以从经去污剂溶解的天然纤维细胞膜中分离出来。乳糖可破坏MP20和半乳糖凝集素-3之间的结合，这表明凝集素位点参与了相互作用。
MP20加入了不断增加的半乳糖凝集素-3配体名单，并且似乎是已鉴定出具有这种特异性的跨膜4超家族的首个代表。
