Insight into the mechanism of cytotoxicity of membrane-permeant psoralenic Kv1.3 channel inhibitors by chemical dissection of a novel member of the family

Abstract

The potassium channel Kv1.3, involved in several important pathologies, is the target of a family of psoralen-based drugs whose mechanism of action is not fully understood. Here we provide evidence for a physical interaction of the mitochondria-located Kv1.3 (mtKv1.3) and Complex I of the respiratory chain and show that this proximity underlies the death-inducing ability of psoralenic Kv1.3 inhibitors. The effects of PAP-1-MHEG (PAP-1, a Kv1.3 inhibitor, with six monomeric ethylene glycol units attached to the phenyl ring of PAP-1), a more soluble novel derivative of PAP-1 and of its various portions on mitochondrial physiology indicate that the psoralenic moiety of PAP-1 bound to mtKv1.3 facilitates the diversion of electrons from Complex I to molecular oxygen. The resulting massive production of toxic Reactive Oxygen Species leads to death of cancer cells expressing Kv1.3. In vivo , PAP-1-MHEG significantly decreased melanoma volume. In summary, PAP-1-MHEG offers insights into the mechanisms of cytotoxicity of this family of compounds and may represent a valuable clinical tool.

An Angiopep2-PAPTP Construct Overcomes the Blood-Brain Barrier. New Perspectives against Brain Tumors

“…Figure 2 shows that there was little dose-dependence of the cytotoxic effects of PAPTP and PAPTPL. This unexpected observation may be attributed to the low solubility in aqueous media of these compounds, an important shortcoming of the family of psoralenic derivatives, including PAP-1 [ 10 ]. We thus determined the solubility of the major molecules of interest.…”

“…A contribution to progress in this direction has been the development of mitochondriotropic variants [ 6 ] of the psoralenic compound 5-(4-phenoxybutoxy)psoralen (PAP-1) [ 7 , 8 ]. These compounds, (3-(4-(4-((7-oxo-7 H -furo[3,2-g]benzopyran-4-yl)oxy)butoxy)phenyl)propyl) triphenyl phosphonium iodide (PAPTP) and (3-(((4-(4-((7-oxo-7 H -furo[3,2-g]chromen-4-yl)oxy) butoxy)phenoxy)carbonyl) amino)propyl)triphenylphosphonium iodide (PCARBTP) ( Figure 1 and Figure S1 ), concentrate in the organelles, bind to and inhibit the K + channel Kv1.3 present in the inner mitochondrial membrane (IMM) [ 9 ], interact with Complex I of the respiratory chain [ 10 ], and thereby cause oxidative stress which selectively kills cancer cells sparing normal ones [ 6 ]. Accumulation in mitochondria is determined by the presence in the molecule of a lipophilic permanent cation (in this case, as most often, triphenylphosphonium (TPP) [ 11 , 12 ]), and is essential.…”

“…As reported here, these peptides have, therefore, been used to build reversible conjugates comprising PAPTP, to verify whether these constructs would be targeted to the brain in the mouse. A previous recent study [ 10 ] has identified the contributions of the component sections of PAP-1 to its pharmacological activity. The compound binds to mtKv1.3—which is physically associated with complex I of the respiratory chain—using the alkoxyphenoxy “arm”.…”

Mitochondrial Ion Channels of the Inner Membrane and Their Regulation in Cell Death Signaling

“…One exception is the voltage-gated Kv1.3, shown to interact with OMM-inserted BAX ( Szabo et al, 2008 ) via critical lysine residues during apoptosis ( Szabo et al, 2011 ; Figure 1 ). The channel becomes inhibited, and via interaction with complex I, Kv1.3 inhibitors trigger ROS release ( Peruzzo et al, 2020 ), leading to PTP opening. This observation inspired the design of a mitochondriotropic inhibitor of the channel that triggered apoptosis and drastically reduced tumor volume of both melanoma and pancreatic ductal adenocarcinoma in vivo .…”

Voltage-Gated Potassium Channels as Regulators of Cell Death

“…Intratumoral injection of Margatoxin, a Kv1.3 inhibitor acting on the plasma membrane Kv1.3, reduced lung cancer volume in vivo ( Jang et al, 2011a ), while intraperitoneal injection of PAP-1, the small molecule inhibitor of this channel, did not reduce tumor volume in an orthotopic melanoma model ( Leanza et al, 2017 ; Peruzzo et al, 2020 ). Two toxins, acting on Kv1.1 (KAaH2) and Kv1.3 (KAaH1 that acts on Kv1.1 as well) derived from the Androctonus australis Hector venom, were shown to inhibit glioma proliferation and migration, at least in vitro ( Aissaoui et al, 2018 ).…”