Monomeric type I and type III transforming growth factor-β receptors and their dimerization revealed by single-molecule imaging

转变生长因素 -- 尾(TGF- 尾) 与二 transmembrane serine/threonine kinase 受体，类型 II (T 尾 R II ) 和类型绑我受体(T 尾 R 我) ，并且一附件受体，类型 III 受体(T 尾 R III ) ，到越过房间膜的 transduce 信号。以前的生物化学的研究建议了那 T 尾 R 我和 T 尾 R III 被先存在 homo-dimers。用到图象绿色的单个分子的显微镜学荧光灯标记蛋白质的膜蛋白质，第一次，我们表明了那 T 尾 R 我和 T 尾 R III 能在低表达式水平作为单体存在。在 TGF-尾 1 刺激之上，我跟随的 T 尾 R 为激活的一般导致 ligand 的受体 dimerization 模型，而是这个过程是 T 尾 R II 依赖。non-kinase 受体 T 尾 R III 的 monomeric 地位面对 TGF-尾 1 是未改变的。随受体表示的增加，两 T 尾 R 我和 T 尾 R III 能在房间表面上被装配进 dimers。

High-resolution imaging of graphene by tip-enhanced coherent anti-Stokes Raman scattering

Coherent anti-Stokes Raman scattering(CARS)is able to enhance molecular signals by vibrational coherence compared to weak Raman signal.The surface or tip enhancement are successful technologies,which make it possible for Raman to detect single molecule with nanometer resolution.However,due to technical diffculties,tip-enhanced CARS(TECARS)is not as successful as expected.For single molecular detection,high sensitivity and resolution are two main challenges.Here,we reported the first single atom layer TECARS imaging on Graphene with the highest resolution about 20 nm,which has ever been reported.The highest EF_(TECARS/CARS) is about 10^(4),the similar order of magnitude with SECARS(EF of tip is usually smaller than that of substrates).Such resolution and sensitivity is promising for medical,biology and chemical applications in the future.

Fusion of clathrin and caveolae endocytic vesicles revealed by line-switching dual-color STED microscopy

Clathrin-and caveolae-mediated endocytosis are the most commonly used pathways for the internalization of cell membrane receptors.However,due to their dimensions are within the diffraction limit,traditional fluorescence microscopy cannot distinguish them and little is known about their interactions underneath cell membrane.In this study,we proposed the line-switching scanning imaging mode for dual-color triplet-state relaxation(T-Rex)stimulated emission depletion(STED)super-resolution microscopy.With this line-switching mode,the cross-talk between the two channels,the side effects from pulse picker and image drift in frame scanning mode can be effectively eliminated.The dual-color super-resolution imaging results in mixed fluorescent beads validated the excellent performance.With this super-resolution microscope,not only the ring-shaped structure of clathrin and caveolae endocytic vesicles,but also their semi-fused structures underneath the cell membrane were distinguished clearly.The resultant infor-mation will greatly facilitate the study of clathrin-and caveolae-mediated receptor endocytosis and signaling process and also our home-built dual-color T-Rex STED microscope with this line-switching imaging mode provides a precise and convenient way to study subcellular-scale protein interactions.

Super-resolution imaging and tracking of TGF-β receptor II on living cells

Single-particle tracking photoactivated localization microscopy(spt PALM) has recently emerged as a powerful tool for high-density imaging and tracking of individual molecules in living cells. In this work, we have monitored and compared the diffusion dynamics of TGF-b type II receptor(Tb RII) at high expression level using both traditional single-particle tracking(SPT) and spt PALM.The ligand-induced aggregation of Tb RII oligomers was further indicated by spt PALM. Due to the capacity of distinguishing and tracking single molecules within diffraction limit, spt PALM outperforms traditional SPT by providing more accurate biophysical information.

Single-molecule imaging reveals the stoichiometry change of epidermal growth factor receptor during transactivation by β_2-adrenergic receptor

Stimulation of G protein-coupled receptors(GPCRs) can lead to the transactivation of the epidermal growth factor receptors(EGFR). The cross-communication between the two signaling pathways regulates several important physiological or pathological processes. However, the molecule mechanism underlying EGFR transactivation remains poorly understood. Here, we aim to study the GPCR-mediated EGFR transactivation process using the single-molecule fluorescence imaging and tracking approach.We found that although EGFR existed as monomers at the plasma membrane of resting cells, they became dimers and thus diffused slower following the activation of β2-adrenergic receptor(β2-AR) by isoproterenol(ISO). We further proved thatβ2-AR-mediated changes of EGFR in stoichiometry and dynamics were mediated by Src kinase. Thus, the observations obtained via the single-molecule imaging and tracking methods shed new insights into the molecular mechanism of EGFR transactivation at single molecule level.