Stabilization of Aliphatic Phosphines by Auxiliary Phosphine Sulfides Offers Zeptomolar Affinity and Unprecedented Selectivity for Probing Biological Cu^I

Abstract

Full elucidation of the functions and homeostatic pathways of biological copper requires tools that can selectively recognize and manipulate this trace nutrient within living cells and tissues, where it exists primarily as Cu . Buffered at attomolar concentrations, intracellular Cu is, however, not readily accessible to commonly employed amine and thioether-based chelators. Herein, we reveal a chelator design strategy in which phosphine sulfides aid in Cu coordination while simultaneously stabilizing aliphatic phosphine donors, producing a charge-neutral ligand with low-zeptomolar dissociation constant and 10 -fold selectivity for Cu over Zn , Fe , and Mn . As illustrated by reversing ATP7A trafficking in cells and blocking long-term potentiation of neurons in mouse hippocampal brain tissue, the ligand is capable of intercepting copper-dependent processes. The phosphine sulfide-stabilized phosphine (PSP) design approach, which confers resistance towards protonation, dioxygen, and disulfides, could be readily expanded towards ligands and probes with tailored properties for exploring Cu in a broad range of biological systems.

Copper bioavailability is a KRAS-specific vulnerability in colorectal cancer

“…To corroborate these findings, we used the recently developed ratiometric Cu(I)-selective fluorescent probe, crisp-17, as another readout for bioavailable Cu 25 . The probe was first validated using the cell-permeant complex CuGTSM (glyoxalbis(N 4 -methyl-3-thiosemicarbazonato) copper(II)) and a Cu(I)-specific chelator (PSP-2) 29 , which confirmed that the probe reversibly responds to changes in cellular Cu levels (Supplementary Fig. 5e, f ).…”

Ratiometric two-photon microscopy reveals attomolar copper buffering in normal and Menkes mutant cells

“…To overcome the limitations of conventional thioether-based Cu(I) chelators, we recently devised an alternative ligand design strategy featuring phosphine sulfide-stabilized phosphine (PSP) donor motifs (18). The electron-withdrawing phosphine sulfide substituents stabilize the central phosphine donor against oxidation while at the same time acting as auxiliary donors for Cu(I) coordination ( Fig.…”

High-affinity Cu(I) chelator PSP-2 as potential anti-angiogenic agent

“…PSP-2 (1,2-bis(bis(dimethylphosphorothioylmethyl)phosphino)ethane) was synthesized as previously described 11 . Avastin was purchased from Kantonsapotheke Zürich (Bevacizumab 25 mg/ml, Kantonsapotheke Zürich, Switzerland).…”

“…We recently reported a membrane-permeant chelator, PSP-2, which binds Cu(I) with low zeptomolar dissociation constant (log K = 20, 25 °C) and exhibits negligible affinity towards other biologically relevant divalent metal cations, including Mn(II), Fe(II), and Zn(II) 11 . Despite the high Cu(I) affinity, PSP-2 revealed low acute toxicity in cell culture up to a concentration of 100 µM over a period of 24 hours.…”

“…Despite the high Cu(I) affinity, PSP-2 revealed low acute toxicity in cell culture up to a concentration of 100 µM over a period of 24 hours. In vitro studies demonstrated that the chelator can intercept intracellular copper trafficking pathways, for example, by reversing copper-induced trafficking of the Menkes protein (ATP7A) or by blocking long-term potentiation of neurons in acute mouse hippocampal tissue slices 11 .…”