Synthesis of Fluorophores that Target Small Molecules to the Endoplasmic Reticulum of Living Mammalian Cells

• Published in: Angewandte Chemie International Edition Vol. 54; no. 33; pp. 9696 - 9699
• Main Authors: Meinig, J. Matthew, Fu, Liqiang, Peterson, Blake R.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 10.08.2015; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: chemical biology; Chemical compounds; cytotoxins; Derivatives; Drug Carriers - chemical synthesis; Drug Carriers - chemistry; Drug Carriers - metabolism; Drug Delivery Systems; Endoplasmic reticulum; Endoplasmic Reticulum - metabolism; Fluorescence; Fluorescent Dyes - chemical synthesis; Fluorescent Dyes - chemistry; Fluorescent Dyes - metabolism; Fluorination; fluorophores; Halogenation; HeLa Cells; Humans; Hydrophobic and Hydrophilic Interactions; Lasers; Nitrofurans - administration & dosage; Pathways; proteasome; Proteins; Warheads; Xanthones - chemical synthesis; Xanthones - chemistry; Xanthones - metabolism; fluorophores; proteasome; cytotoxins; chemical biology; endoplasmic reticulum
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201504156

The endoplasmic reticulum (ER) plays critical roles in the processing of secreted and transmembrane proteins. To deliver small molecules to this organelle, we synthesized fluorinated hydrophobic analogues of the fluorophore rhodol. These cell‐permeable fluorophores are exceptionally bright, with quantum yields of around 0.8, and they were found to specifically accumulate in the ER of living HeLa cells, as imaged by confocal laser scanning microscopy. To target a biological pathway controlled by the ER, we linked a fluorinated hydrophobic rhodol to 5‐nitrofuran‐2‐acrylaldehyde. In contrast to an untargeted nitrofuran warhead, delivery of this electrophilic nitrofuran to the ER by the rhodol resulted in cytotoxicity comparable to the ER‐targeted cytotoxin eeyarestatin I, and specifically inhibited protein processing by the ubiquitin–proteasome system. Fluorinated hydrophobic rhodols are outstanding fluorophores that enable the delivery of small molecules for targeting ER‐associated proteins and pathways. On target: Fluorinated hydrophobic analogues of rhodol accumulate in the endoplasmic reticulum (ER) of HeLa cells. When this highly fluorescent ER‐targeting motif was linked to a 5‐nitrofuran warhead, the ubiquitin–proteasome system was selectively inhibited. These rhodol derivatives thus provide a new method for the delivery of small molecules for targeting ER‐associated proteins and pathways.