TY - JOUR A1 - Groeneweg, Femke L. A1 - van Royen, Martin E. A1 - Fenz, Susanne A1 - Keizer, Veer I. P. A1 - Geverts, Bart A1 - Prins, Jurrien A1 - de Kloet, E. Ron A1 - Houtsmuller, Adriaan B. A1 - Schmidt, Thomas S. A1 - Schaaf, Marcel J. M. T1 - Quantitation of Glucocorticoid Receptor DNA-Binding Dynamics by Single-Molecule Microscopy and FRAP JF - PLOS ONE N2 - Recent advances in live cell imaging have provided a wealth of data on the dynamics of transcription factors. However, a consistent quantitative description of these dynamics, explaining how transcription factors find their target sequences in the vast amount of DNA inside the nucleus, is still lacking. In the present study, we have combined two quantitative imaging methods, single-molecule microscopy and fluorescence recovery after photobleaching, to determine the mobility pattern of the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR), two ligand-activated transcription factors. For dexamethasone-activated GR, both techniques showed that approximately half of the population is freely diffusing, while the remaining population is bound to DNA. Of this DNA-bound population about half the GRs appeared to be bound for short periods of time (similar to 0.7 s) and the other half for longer time periods (similar to 2.3 s). A similar pattern of mobility was seen for the MR activated by aldosterone. Inactive receptors (mutant or antagonist-bound receptors) show a decreased DNA binding frequency and duration, but also a higher mobility for the diffusing population. Likely, very brief (<= 1 ms) interactions with DNA induced by the agonists underlie this difference in diffusion behavior. Surprisingly, different agonists also induce different mobilities of both receptors, presumably due to differences in ligand-induced conformational changes and receptor complex formation. In summary, our data provide a consistent quantitative model of the dynamics of GR and MR, indicating three types of interactions with DNA, which fit into a model in which frequent low-affinity DNA binding facilitates the search for high-affinity target sequences. KW - NF-KAPPA-B KW - image correlation spectroscopy KW - human mineralocorticoid receptor KW - nuclear-pore complexes KW - in-vivo KW - living cells KW - mobility KW - transcription KW - protein KW - reveals Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-117085 VL - 9 IS - 3 ER - TY - JOUR A1 - Hartel, Andreas J.W. A1 - Glogger, Marius A1 - Jones, Nicola G. A1 - Abuillan, Wasim A1 - Batram, Christopher A1 - Hermann, Anne A1 - Fenz, Susanne F. A1 - Tanaka, Motomu A1 - Engstler, Markus T1 - N-glycosylation enables high lateral mobility of GPI-anchored proteins at a molecular crowding threshold JF - Nature Communications N2 - The protein density in biological membranes can be extraordinarily high, but the impact of molecular crowding on the diffusion of membrane proteins has not been studied systematically in a natural system. The diversity of the membrane proteome of most cells may preclude systematic studies. African trypanosomes, however, feature a uniform surface coat that is dominated by a single type of variant surface glycoprotein (VSG). Here we study the density-dependence of the diffusion of different glycosylphosphatidylinositol-anchored VSG-types on living cells and in artificial membranes. Our results suggest that a specific molecular crowding threshold (MCT) limits diffusion and hence affects protein function. Obstacles in the form of heterologous proteins compromise the diffusion coefficient and the MCT. The trypanosome VSG-coat operates very close to its MCT. Importantly, our experiments show that N-linked glycans act as molecular insulators that reduce retarding intermolecular interactions allowing membrane proteins to function correctly even when densely packed. KW - parasitology KW - cellular imaging KW - membrane biophysics KW - single-molecule biophysics Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-171368 VL - 7 ER -