Organic anion transporting polypeptides (OATPs) were found to readily deliver membrane impermeable, tetrazine bearing fluorescent probes into cells. This feature was explored in OATP3A1 conditioned bio-orthogonal labeling schemes of various intracellular proteins in live cells. Confocal microscopy and super-resolution microscopy (STED) studies have shown that highly specific and efficient staining of the selected intracellular proteins can be achieved with the otherwise non-permeable probes when OATP3A1 is present in the cell membrane of cells. Such a transport protein linked bio-orthogonal labeling scheme is believed to be useful in OATP3A1 activity-controlled protein expression studies in the future.
Keywords: cell permeability; confocal microscopy; flow cytometry; intracellular labeling; large Stokes shift fluorescent probes; live cell bio-orthogonal modification; organic anion transporter polypeptide 3A1; self-labeling enzyme tags; super-resolution microscopy.