Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, Maryland.
Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, Maryland; Johns Hopkins Institute for NanoBioTechnology, The Johns Hopkins University, Baltimore, Maryland; Johns Hopkins Physical Sciences-Oncology Center, The Johns Hopkins University, Baltimore, Maryland; Center of Cancer Nanotechnology Excellence, The Johns Hopkins University, Baltimore, Maryland.
Biophys J. 2012 Aug 8;103(3):415-423. doi: 10.1016/j.bpj.2012.06.039.
CD44 is a multifunctional glycoprotein that binds to hyaluronan and fibrin(ogen). Alternative splicing is responsible for the generation of numerous different isoforms, the smallest of which is CD44s. Insertion of variant exons into the extracellular membrane proximal region generates the variant isoforms (CD44v). Here, we used force spectroscopy to delineate the biophysical and molecular requirements of CD44-HA and CD44-fibrin(ogen) interactions at the single-molecule level. CD44v-HA and CD44s-HA single bonds exhibit similar kinetic and micromechanical properties because the HA-binding motif on CD44 is common to all of the isoforms. Although this is the primary binding site, O- and N-linked glycans and sulfation also contribute to the tensile strength of the CD44-HA bond. The CD44s-fibrin pair has a lower unstressed dissociation rate and a higher tensile strength than CD44s-fibrinogen but is weaker than the CD44-HA bond. In contrast to CD44-HA binding, the molecular interaction between CD44 and fibrin(ogen) is predominantly mediated by the chondroitin sulfate and dermatan sulfate on CD44. Blocking sulfation on CD44s modestly decreases the tensile strength of CD44s-fibrin(ogen) binding, which is in stark contrast to CD44v-fibrin interaction. Collectively, the results obtained by force spectroscopy in conjunction with biochemical interventions enable us to delineate the biophysical parameters and molecular constituents of CD44 binding to hyaluronan and fibrin(ogen).
CD44 是一种多功能糖蛋白，可与透明质酸和纤维蛋白原（ogen）结合。可变剪接负责产生许多不同的异构体，其中最小的是 CD44s。将变体外显子插入细胞外膜近侧区域会产生变体异构体（CD44v）。在这里，我们使用力谱法在单分子水平上描绘 CD44-HA 和 CD44-纤维蛋白原（ogen）相互作用的生物物理和分子要求。CD44v-HA 和 CD44s-HA 单键表现出相似的动力学和微观力学特性，因为 CD44 上的 HA 结合基序是所有异构体共有的。尽管这是主要的结合位点，但 O-和 N-连接的聚糖和硫酸化也有助于 CD44-HA 键的拉伸强度。CD44s-纤维蛋白对的未受应力解离率较低，拉伸强度较高，但比 CD44-HA 键弱。与 CD44-HA 结合相反，CD44 与纤维蛋白原（ogen）之间的分子相互作用主要由 CD44 上的硫酸软骨素和硫酸皮肤素介导。阻断 CD44s 上的硫酸化会适度降低 CD44s-纤维蛋白原（ogen）结合的拉伸强度，这与 CD44v-纤维蛋白相互作用形成鲜明对比。总的来说，力谱法与生化干预相结合获得的结果使我们能够描绘 CD44 与透明质酸和纤维蛋白原（ogen）结合的生物物理参数和分子成分。
