Glutathione-Responsive Selenosulfide Prodrugs as a Platform Strategy for Potent and Selective Mechanism-Based Inhibition of Protein Tyrosine Phosphatases

Abstract

Dysregulation of protein tyrosine phosphorylation has been implicated in a number of human diseases, including cancer, diabetes, and neurodegenerative diseases. As a result of their essential role in regulating protein tyrosine phosphorylation levels, protein tyrosine phosphatases (PTPs) have emerged as important yet challenging therapeutic targets. Here we report on the development and application of a glutathione-responsive motif to facilitate the efficient intracellular delivery of a novel class of selenosulfide phosphatase inhibitors for the selective active site directed inhibition of the targeted PTP by selenosulfide exchange with the active site cysteine. The strategy leverages the large difference in extracellular and intracellular glutathione levels to deliver selenosulfide phosphatase inhibitors to cells. As an initial exploration of the prodrug platform and the corresponding selenosulfide covalent inhibitor class, potent and selective inhibitors were developed for two therapeutically relevant PTP targets: the Mycobacterium tuberculosis virulence factor mPTPA and the CNS-specific tyrosine phosphatase, striatal-enriched protein tyrosine phosphatase (STEP). The lead selenosulfide inhibitors enable potent and selective inhibition of their respective targets over a panel of human PTPs and a representative cysteine protease. Kinetic parameters of the inhibitors were characterized, including reversibility of inhibition and rapid rate of GSH exchange at intracellular GSH concentrations. Additionally, active site covalent inhibitor-labeling with an mPTPA inhibitor was rigorously confirmed by mass spectrometry, and cellular activity was demonstrated with a STEP prodrug inhibitor in cortical neurons.

Diselenolane-mediated cellular uptake

“…The similar characteristics of ETP 5 and SeL 7 recorded by this method point toward an intriguing multitarget thiol hopping mechanism along so far unexplored routes to account for the efficient cytosolic delivery of these most powerful systems. 22 , 25 …”

Selenosulfides Tethered to gem‐Dimethyl Esters: A Robust and Highly Versatile Framework for H2S Probe Development

“…To achieve this desired versatility without comprising reactivity and selectivity, we conjectured that the employment of a selenosulfide functionality would be key for accessing a probe with these desired attributes. Although selenosulfides have been rarely reported within the chemical literature, we reasoned that reactivity differences between selenium and sulfur could be exploited such that the selenium half, when tethered to a second electrophilic partner, would effectively scavenge and detect H 2 S, while the sulfur half would provide a suitable handle for mediating its physicochemical properties. Therefore, we first synthesized selenosulfide 1 from 3‐bromopivalic acid (see the Supporting Information) as it provided an amino group for subsequent conjugation reactions.…”

Equilibrium between tri‐ and tetra‐coordinate chalcogenuranes is critical for cysteine protease inhibition

“…15 Among electrophilic organochalcogen species, the hypervalent derivatives (+4 oxidation state) shows reactivities toward thiols, which imply inhibition of cysteine cathepsins, 5,[16][17][18] arginine phosphatases 19 or tyrosine phosphatases. [20][21][22] The overexpression and exacerbate activity of cysteine cathepsins are related to several pathologies like cancer, arthritis, atherosclerosis, osteoporosis, cardiovascular, and parasitic diseases. 16,[23][24][25] In such conditions, the inhibition of these enzymes is desired and considered therapeutical strategies.…”

“…The antiviral activity may be related to the inhibition of the viral cysteine proteases 3CL Pro (also called MPro) and the papain‐like protease (PL Pro ) 15 . Among electrophilic organochalcogen species, the hypervalent derivatives (+4 oxidation state) shows reactivities toward thiols, which imply inhibition of cysteine cathepsins, 5,16–18 arginine phosphatases 19 or tyrosine phosphatases 20–22 …”