TY - JOUR A1 - Boltz, Horst-Holger A1 - Sirbu, Alexei A1 - Stelzer, Nina A1 - de Lanerolle, Primal A1 - Winkelmann, Stefanie A1 - Annibale, Paolo T1 - The Impact of Membrane Protein Diffusion on GPCR Signaling JF - Cells N2 - Spatiotemporal signal shaping in G protein-coupled receptor (GPCR) signaling is now a well-established and accepted notion to explain how signaling specificity can be achieved by a superfamily sharing only a handful of downstream second messengers. Dozens of Gs-coupled GPCR signals ultimately converge on the production of cAMP, a ubiquitous second messenger. This idea is almost always framed in terms of local concentrations, the differences in which are maintained by means of spatial separation. However, given the dynamic nature of the reaction-diffusion processes at hand, the dynamics, in particular the local diffusional properties of the receptors and their cognate G proteins, are also important. By combining some first principle considerations, simulated data, and experimental data of the receptors diffusing on the membranes of living cells, we offer a short perspective on the modulatory role of local membrane diffusion in regulating GPCR-mediated cell signaling. Our analysis points to a diffusion-limited regime where the effective production rate of activated G protein scales linearly with the receptor–G protein complex’s relative diffusion rate and to an interesting role played by the membrane geometry in modulating the efficiency of coupling Y1 - 2022 U6 - https://doi.org/10.3390/cells11101660 VL - 11 IS - 10 SP - 1660 ER - TY - JOUR A1 - Boltz, Horst-Holger A1 - Sirbu, Alexei A1 - Stelzer, Nina A1 - Lohse, Martin J. A1 - Schütte, Christof A1 - Annibale, Paolo T1 - Quantitative spectroscopy of single molecule interaction times JF - Optic Letters N2 - Single molecule fluorescence tracking provides information at nanometer-scale and millisecond-temporal resolution about the dynamics and interaction of individual molecules in a biological environment. While the dynamic behavior of isolated molecules can be characterized well, the quantitative insight is more limited when interactions between two indistinguishable molecules occur. We address this aspect by developing a theoretical foundation for a spectroscopy of interaction times, i.e., the inference of interaction from imaging data. A non-trivial crossover between a power law to an exponential behavior of the distribution of the interaction times is highlighted, together with the dependence of the exponential term upon the microscopic reaction affinity. Our approach is validated with simulated and experimental datasets. Y1 - 2021 U6 - https://doi.org/10.1364/OL.413030 VL - 46 IS - 7 SP - 1538 EP - 1541 ER -