title: Influence of Histidine-Containing Tags on the Biodistribution of ADAPT Scaffold Proteins.
abstract: Engineered scaffold proteins (ESP) are high-affinity binders that can be used as probes for radionuclide imaging. Histidine-containing tags enable both efficient purification of ESP and radiolabeling with (99m)Tc(CO)3. Earlier studies demonstrated that the use of a histidine-glutamate-histidine-glutamate-histidine-glutamate (HE)3-tag instead of the commonly used hexahistidine (H6)-tag reduces hepatic uptake of radiolabeled ESP and short peptides. Here, we investigated the influence of histidine-containing tags on the biodistribution of a novel type of ESP, ADAPTs. A series of anti-HER2 ADAPT probes having H6- or (HE)3-tags in the N-termini were prepared. The constructs, (HE)3-ADAPT6 and H6-ADAPT6, were labeled with two different nuclides, (99m)Tc or (111)In. The labeling with (99m)Tc(CO)3 utilized the histidine-containing tags, while (111)In was attached through a maleimido derivative of DOTA conjugated to the N-terminus. For (111)In-labeled ADAPTs, the use of (HE)3 provided a significantly (p < 0.05) lower hepatic uptake at 1 h after injection, but there was no significant difference in hepatic uptake of (111)In-(HE)3-ADAPT6 and H6-ADAPT6 at later time points. Interestingly, in the case of (99m)Tc, (99m)Tc(CO)3-H6-ADAPT6 provided significantly (p < 0.05) lower uptake in a number of normal tissues and was more suitable as an imaging probe. Thus, the influence of histidine-containing tags on the biodistribution of the novel ADAPT scaffold proteins was different compared to its influence on other ESPs studied so far. Apparently, the effect of a histidine-containing tag on the biodistribution is highly dependent on the scaffold composition of the ESP.
authors.affiliation: Department of Protein Technology, KTH - Royal Institute of Technology , SE-10691, Stockholm, Sweden.
authors.forename: Sarah
authors.initials: S
authors.lastname: Lindbo
authors.forename: Javad
authors.initials: J
authors.lastname: Garousi
authors.affiliation: Department of Protein Technology, KTH - Royal Institute of Technology , SE-10691, Stockholm, Sweden.
authors.forename: Mikael
authors.initials: M
authors.lastname: Åstrand
authors.forename: Hadis
authors.initials: H
authors.lastname: Honarvar
authors.forename: Anna
authors.initials: A
authors.lastname: Orlova
authors.affiliation: Department of Protein Technology, KTH - Royal Institute of Technology , SE-10691, Stockholm, Sweden.
authors.forename: Sophia
authors.initials: S
authors.lastname: Hober
authors.forename: Vladimir
authors.initials: V
authors.lastname: Tolmachev
mesh_terms: D000595:Amino Acid Sequence; D006639:Histidine / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D014018:Tissue Distribution
chemical_list: D011506:Proteins; D006639:Histidine