ABSTRACT
An ultra-high fluorescence enhancement for two dyes on photonic crystal films was achieved to construct a two-color immuno-dot blot assay. This assay was demonstrated to simultaneously detect chemokine receptor co-expressed in cancer cells and reveal their co-operative and subtle changes after binding with respective ligands and drugs.
Subject(s)
Color , Fluorescence , Fluorescent Dyes/chemistry , In Situ Hybridization, Fluorescence , Receptors, Chemokine/analysis , HeLa Cells , Humans , Receptors, Chemokine/biosynthesisABSTRACT
The relationship between the oligomeric status and functions of chemokine receptor CCR3 is still controversial. We use total internal reflection fluorescence microscopy at the single-molecule level to visualize the oligomeric status of CCR3 and its regulation of the membrane of stably transfected T-REx-293 cells. We find that the population of the dimers and oligomers of CCR3 can be modulated by the binding of ligands. Natural agonists can induce an increase in the level of dimers and oligomers at high concentrations, whereas antagonists do not have a significant influence on the oligomeric status. Moreover, monomeric CCR3 exhibits a stronger chemotactic response in the migration assay of stably transfected CCR3 cells. Together, these data support the notion that CCR3 exists as a mixture of monomers and dimers under nearly physiological conditions and the monomeric CCR3 receptor is the minimal functional unit in cellular signaling transduction. To the best of our knowledge, these results constitute the first report of the oligomeric status of CCR3 and its regulation.
Subject(s)
Microscopy, Fluorescence/methods , Receptors, CCR3/metabolism , Single Molecule Imaging/methods , Cell Line , Cell Membrane/metabolism , Chemotaxis , Dose-Response Relationship, Drug , Humans , Ligands , Photobleaching , Protein Multimerization , Receptors, CCR3/agonists , Receptors, CCR3/antagonists & inhibitors , Recombinant Proteins/metabolism , Signal TransductionABSTRACT
The role of dimerization and oligomerization of G-protein-coupled receptors in their signal transduction is highly controversial. Delineating this issue can greatly facilitate rational drug design. With single-molecule imaging, we show that chemokine receptor CXCR4 exists mainly as a monomer in normal mammalian living cells and forms dimers and higher-order oligomers at a high expression level, such as in cancer cells. Chemotaxis tests demonstrate that the signal transduction activity of CXCR4 does not depend only on its expression level, indicating a close relation with the oligomeric status of CXCR4. Moreover, binding ligands can effectively upregulate or downregulate the oligomeric level of CXCR4, which suggests that binding ligands may realize their pivotal roles by regulating the oligomeric status of CXCR4 rather than by simply inducing conformational changes.
Subject(s)
Protein Multimerization/physiology , Receptors, CXCR4/metabolism , Benzylamines , Cell Line, Transformed , Cell Line, Tumor , Chemokine CXCL12/pharmacology , Cyclams , Heterocyclic Compounds/pharmacology , Humans , Ligands , Microscopy, Fluorescence , Oligopeptides/pharmacology , Protein Multimerization/drug effects , Receptors, CXCR4/agonists , Receptors, CXCR4/chemistryABSTRACT
Fluorescence imaging requires bioselective, sensitive, nontoxic molecular probes to detect the precise location of lesions for fundamental research and clinical applications. Typical inorganic semiconductor nanomaterials with large sizes (>10 nm) can offer high-quality fluorescence imaging due to their fascinating optical properties but are limited to low selectivity as well as slow clearance pathway. We here report an N- and O-rich carbogenic small molecular complex (SMC, MW < 1000 Da) that exhibits high quantum yield (up to 80%), nucleic acid-binding enhanced excitation-dependent fluorescence (EDF), and a near-infrared (NIR) emission peaked at 850 nm with an ultralarge Stokes shift (â¼500 nm). SMCs show strong rRNA affinity, and the resulting EDF enhancement allows multicolor visualization of nucleoli in cells for clear statistics. Furthermore, SMCs can be efficiently accumulated in tumor in vivo after injection into tumor-bearing mice. The NIR emission affords high signal/noise ratio imaging for delineating the true extent of tumor. Importantly, about 80% of injected SMCs can be rapidly excreted from the body in 24 h. No appreciable toxicological responses were observed up to 30 days by hematological, biochemical, and pathological examinations. SMCs have great potential as a promising nucleolus- and tumor-specific agent for medical diagnoses and biomedical research.
