The sodium–iodide symporter (NIS) is an integral membrane protein that plays a crucial role in iodide accumulation, especially in the thyroid. As for many other membrane proteins, its intracellular sorting and distribution have a tremendous effect on its function, and constitute an important aspect of its regulation. Many short sequences have been shown to contribute to protein trafficking along the sorting or endocytic pathways. Using bioinformatics tools, we identified such potential sites on human NIS [tyrosine-based motifs, SH2-(Src homology 2), SH3- and PDZ (post-synaptic density-95/discs large tumour suppressor/zonula occludens-1)-binding motifs, and diacidic, dibasic and dileucine motifs] and analysed their roles using mutagenesis. We found that several of these sites play a role in protein stability and/or targeting to the membrane. Aside from the mutation at position 178 (SH2 plus tyrosine-based motif) that affects iodide uptake, the most drastic effect is associated with the mutation of an internal PDZ-binding motif at position 121 that completely abolishes NIS expression at the plasma membrane. Mutating the sites located on the C-terminal domain of the protein has no effect except for the creation of a diacidic motif that decreases the total NIS protein level without affecting its expression at the plasma membrane.

Macrophages (in green) treated with polyethylene terephthalate nanoparticles (in red) internalize them, which induces various cellular and immune responses.

Plastics are persistent in the environment, which suggests that they may induce adverse effects due to their progressive accumulation over time.

New chemicals including nanomaterials are being created and spread at high speed. In the E.U., REACH compliance imposes to manufacturers some tests but they are limited. Often, they cannot detect anything if the cells or organisms are able to overcome the toxic effect at the macroscopic level, preventing the suspicion of a potential long-term effect. Concerning bacteria that are essential for ecosystems and human health (microbiota), they are often considered as a whole in a consortium and only global parameters are measured. To overcome these limitations, we performed a study on the essential soil bacterium Bacillus subtilis. Two types of biofilm that are closer to its natural growth mode (particularly around plant roots) than the usual liquid type culture have been assayed: pellicle biofilm and swarming. We then used the power of shotgun proteomics to analyze in details these two somehow similar modes of cultures. Several physiological and metabolic patterns including proteins implicated in sporulation have shown significant differences. The effect of two types of nanoparticles (silicon and cerium oxide nanoparticles) has then been studied in the same way. This allowed us to investigate in details the response of the bacteria and focus on the differences observed depending on the biofilm type. This clearly highlighted the importance of testing several growth conditions and pinpointed the power of proteomics.