Biology subjects

Pfaff, P.

Publications and source records attributed to Pfaff, P..

3 recordsLinked to original sources

bioRxiv2026

A photoswitchable cannabinoid for precision treatment of refractory seizures in a mouse epilepsy model

Temporal lobe epilepsy (TLE) has an unmet need for precision treatments targeting the seizure focus while avoiding effects on other body parts to minimise side effects. Photopharmacology could enable precision treatment by combining systemic administration of a photoswitchable drug with implantation of an optic fibre in the epileptic focus to induce light-dependent drug conversion from an inactive to an active configuration that interacts with its target receptor to suppress seizures. The photoswitchable {Delta}9-tetrahydrocannabinol ({Delta}9-THC) derivative, azo-THC-3, transitions from an inactive trans to an active cis configuration upon UV irradiation. We demonstrate that local or systemic administration of azo-THC-3 and local UV irradiation in the hippocampus supresses difficult-to-treat seizures in the intrahippocampal kainic acid mouse model of TLE. Furthermore, our findings illustrate that the photoswitch strategy avoids hypolocomotion, a common side effect of systemic {Delta}9-THC administration. As such, we provide the first demonstration of seizure suppression with the systemic administration of a photoswitchable compound and its local photoactivation in the seizure focus. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=133 SRC="FIGDIR/small/720358v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@1e42794org.highwire.dtl.DTLVardef@1e26891org.highwire.dtl.DTLVardef@13f2b6forg.highwire.dtl.DTLVardef@3c8e48_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2026

GAP mimetic activity of pan-Ras TCI daraxonrasib synergizes with K-Ras Switch-II pocket inhibition

Tricomplex inhibitors (TCIs) are a novel class of direct Ras inhibitors that target the GTP-bound Ras(on) state trough recruitment of Cyclophilin A. Daraxonrasib (RMC-6236) is a pan-Ras TCI that was recently shown to restore GTPase activity of G12-mutant Ras proteins. Structural analysis of a pan-Ras TCI bound to K-Ras(GDP- AlF3) reveals a transition-state arrangement of Tyr32 and Gln61 that closely resembles endogenous GTPase- GAP complexes. This includes a closed Switch-I conformation engaging the cis-GTPase machinery in a manner analogous to non-arginine-finger GAPs such as RanGAP. These observations position pan-Ras TCIs as pharmacologic GAP mimetics. The GTPase-promoting activity of daraxonrasib suggests synergy with Switch-II pocket K-Ras inhibitors, including the approved GDP-state selective K-Ras G12C inhibitor adagrasib (MRTX-849), whose engagement of K-Ras(GTP) is kinetically constrained by slow endogenous hydrolysis of the mutant GTPase. We demonstrate that daraxonrasib sensitizes K-Ras(GTP) to adagrasib labeling in both recombinant protein and cellular context. In K-Ras G12C and G12D mutant cell lines, combinations of daraxonrasib with adagrasib or HRS-4642 (MRTX-1133 analog) yield more rapid K-Ras engagement, rapid p-ERK suppression, and significant Loewe synergy scores in viability assays. These findings establish GAP mimetics as rational and potent combination partners for SW-II inhibitors. The synergistic combination has potential to deepen and prolong pathway suppression while enabling dose reductions that may mitigate on-target toxicity and resistance.

cancer biology↗

bioRxiv2025

Deazaguanylation is a nucleobase-protein conjugation required for type IV CBASS immunity

7-deazapurines are nucleobase analogs essential for nucleic acid modifications in nearly all cellular life. Here, we discover a role for 7-deazapurines in protein modification within type IV CBASS anti-phage defense and define functions for CBASS ancillary proteins Cap9 and Cap10 in nucleobase-protein conjugation. A structure of Cap10 reveals a tRNA transglycosylase-family enzyme remodeled to bind the modified N-terminus of a partner cGAS/DncV-like nucleotidyltransferase linked to a 7-amido-7-deazaguanine (NDG) nucleobase. The structure of Cap9 explains how this QueC-like enzyme co-opts a 7-deazapurine biosynthetic reaction mechanism for NDG conjugation. We demonstrate that Cap9, Cap10, and NDG conjugation are essential for host defense against phage infection. Our results define a previously unknown 7-deazapurine protein modification and explain how nucleobase biosynthetic machinery has been repurposed for antiviral immunity.

microbiology↗