title: Accumulation of FlAsH/Lumio Green in active mitochondria can be reversed by beta-mercaptoethanol for specific staining of tetracysteine-tagged proteins.
abstract: Recent advances in the field of small molecule labels for live cell imaging promise to overcome some of the limitations set by the size of fluorescent proteins. We tested the tetracysteine-biarsenical labeling system in live cell fluorescence microscopy of reggie-1/flotillin-2 in HeLa and N2a cells. In both cell types, the biarsenical staining reagent FlAsH/Lumio Green accumulated in active mitochondria and led to mitochondrial swelling. This is indicative of toxic side effects caused by arsenic, which should be considered when this labeling system is to be used in live cell imaging. Mitochondrial accumulation of FlAsH/Lumio Green was reversed by addition of low concentrations of thiol-containing reagents during labeling and a subsequent high stringency thiol wash. Both ethanedithiol and beta-mercaptoethanol proved to be effective. We therefore established a staining protocol using beta-mercaptoethanol as thiol binding site competitor resulting in a specific staining of tetracysteine-tagged reggie-1/flotillin-2 of adequate signal to noise ratio, so that the more toxic and inconvenient ethanedithiol could be avoided. Furthermore, we show that staining efficiency was greatly enhanced by introducing a second tetracysteine sequence in tandem.
authors.affiliation: Developmental Neurobiology Group, Department of Biology, University of Konstanz, Universitaetsstr. 10, 78457, Konstanz, Germany. Matthiaslanghorst@email.de
authors.forename: Matthias F
authors.initials: MF
authors.lastname: Langhorst
authors.forename: Selda
authors.initials: S
authors.lastname: Genisyuerek
authors.forename: Claudia A O
authors.initials: CA
authors.lastname: Stuermer
mesh_terms: D003545:Cysteine / Q000032:analysis*; D005452:Fluoresceins / Q000032:analysis* / Q000378:metabolism; D005456:Fluorescent Dyes / Q000032:analysis* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry; D008623:Mercaptoethanol / Q000737:chemistry* / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D009942:Organometallic Compounds / Q000032:analysis* / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D013194:Staining and Labeling / Q000379:methods*
chemical_list: C113276:4',5'-bis(1,3,2-dithioarsolan-2-yl)fluorescein; D005452:Fluoresceins; D005456:Fluorescent Dyes; D008565:Membrane Proteins; D009942:Organometallic Compounds; C106354:flotillins; D008623:Mercaptoethanol; D003545:Cysteine