Parallel Fourier ptychographic microscopy for high-throughput screening with 96 cameras (96 Eyes)

We report the implementation of a parallel microscopy system (96 Eyes) that is capable of simultaneous imaging of all wells on a 96-well plate. The optical system consists of 96 microscopy units, where each unit is made out of a four element objective, made through a molded injection process, and a low cost CMOS camera chip. By illuminating the sample with angle varying light and applying Fourier Ptychography, we can improve the effective brightfield imaging numerical aperture of the objectives from 0.23 to 0.3, and extend the depth of field from ±5 μm to ±15 μm. The use of Fourier Ptychography additionally allows us to computationally correct the objectives’ aberrations out of the rendered images, and provides us with the ability to render phase images. The 96 Eyes acquires raw data at a rate of 0.7 frame per second (all wells) and the data are processed with 4 cores of graphical processing units (GPUs; GK210, Nvidia Tesla K80, USA). The system is also capable of fluorescence imaging (excitation = 465 nm, emission = 510 nm) at the native resolution of the objectives. We demonstrate the capability of this system by imaging S1P₁-eGFP-Human bone osteosarcoma epithelial (U2OS) cells.

S1P1 Modulator-Induced G αi Signaling and β-Arrestin Recruitment Are Both Necessary to Induce Rapid and Efficient Reduction of Blood Lymphocyte Count In Vivo

S1P₁ (sphingosine-1-phosphate receptor 1) agonists prevent lymphocyte egress from secondary lymphoid organs and cause a reduction in the number of circulating blood lymphocytes. We hypothesized that S1P₁ receptor modulators with pathway-selective signaling properties could help to further elucidate the molecular mechanisms involved in lymphocyte trapping. A proprietary S1P₁ receptor modulator library was screened for compounds with clear potency differences in β-arrestin recruitment and G protein alpha i subunit (G _αi) protein-mediated signaling. We describe here the structure-activity relationships of highly potent S1P₁ modulators with apparent pathway selectivity for β-arrestin recruitment. The most differentiated compound, D3-2, displayed a 180-fold higher potency in the β-arrestin recruitment assay (EC₅₀ 0.9 nM) compared with the G _αi-activation assay (167 nM), whereas ponesimod, a S1P₁ modulator that is currently in advanced clinical development in multiple sclerosis, was equipotent in both assays (EC₅₀ 1.5 and 1.1 nM, respectively). Using these novel compounds as pharmacological tools, we showed that although a high potency in β-arrestin recruitment is required to fully internalize S1P₁ receptors, the potency in inducing G _αi signaling determines the rate of receptor internalization in vitro. In contrast to ponesimod, the compound D3-2 did not reduce the number or circulating lymphocytes in rats despite high plasma exposures. Thus, for rapid and maximal S1P₁ receptor internalization a high potency in both G _αi signaling and β-arrestin recruitment is mandatory and this translates into efficient reduction of the number of circulating lymphocytes in vivo.

Structural biology of the S1P1 receptor

The sphingosine 1 phosphate receptor family has been studied widely since the initial discovery of its first member, endothelium differentiation gene 1. Since this initial discovery, the family has been renamed and the primary member of the family, the S1P1 receptor, has been targeted for a variety of disease indications and successfully drugged for the treatment of patients with relapsing multiple sclerosis. Recently, the three-dimensional structure of the S1P1 receptor has been determined by X-ray crystallography and the specifics of the sphingosine 1 phosphate ligand binding pocket mapped. Key structural features for the S1P1 receptor will be reviewed and the potential binding modes of additional pharmacologically active agents against the receptor will be analyzed in an effort to better understand the structural basis of important receptor-ligand interactions.