title: Fluorine-18 labeling of phosphopeptides: a potential approach for the evaluation of phosphopeptide metabolism in vivo.
abstract: Phosphopeptides are very useful reagents to study signal transduction pathways related with cellular protein phosphorylation/dephosphorylation. Phosphopeptides have also been identified as important drug candidates to modulate intracellular signaling mechanisms through targeting phosphotyrosine, phosphoserine, or phosphothreonine residue-binding protein domains. In this report, we describe the development of a convenient method for the mild and sufficient radiolabeling of phosphopeptides with the short-lived positron emitter fluorine-18 (18F) to allow radiopharmacological studies on phosphopeptide metabolism in vivo by means of positron emission tomography (PET). Radiolabeling was accomplished via conjugation of the N-terminus of polo-box domain (PBD)-binding phosphopeptide H-Met-Gln-Ser-pThr-Pro-Leu-OH with the bifunctional labeling agent N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB) in reproducible isolated radiochemical yields of 25-28%. Radiopharmacological evaluation in vitro and in vivo of radiolabeled phosphopeptide [18F]FB-Met-Gln-Ser-pThr-Pro-Leu-OH [18F]-3 and its non-phosphorylated analog [18F]FB-Met-Gln-Ser-Thr-Pro-Leu-OH [18F]-4 involved metabolic stability, cell uptake studies, and small animal PET experiments. Radiolabeled phosphopeptide [18F]-3 showed a remarkable high metabolic stability in vivo compared to the corresponding non-phosphorylated peptide [18F]-4. The presented method indicates that radiolabeling of phosphopeptides with [18F]SFB is a promising approach for studying phosphopeptide metabolism in vivo.
authors.affiliation: Institute of Radiopharmacy, Research Center Dresden-Rossendorf, Dresden, Germany.
authors.forename: Susan
authors.initials: S
authors.lastname: Richter
authors.forename: Ralf
authors.initials: R
authors.lastname: Bergmann
authors.forename: Jens
authors.initials: J
authors.lastname: Pietzsch
authors.forename: Theres
authors.initials: T
authors.lastname: Ramenda
authors.forename: Jörg
authors.initials: J
authors.lastname: Steinbach
authors.forename: Frank
authors.initials: F
authors.lastname: Wuest
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D005462:Fluorine Radioisotopes; D006801:Humans; D007553:Isotope Labeling / Q000379:methods*; D008297:Male; D009842:Oligopeptides / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology*; D010750:Phosphoproteins / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D049268:Positron-Emission Tomography / Q000379:methods*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D005462:Fluorine Radioisotopes; D009842:Oligopeptides; D010750:Phosphoproteins