Biology subjects

Biou, V.

Publications and source records attributed to Biou, V..

3 recordsLinked to original sources

bioRxiv2026

Structural and cellular insights into the inhibition of the drug efflux activity of the HEDGEHOG receptor PATCHED1

PTCH1, the receptor for the Sonic Hedgehog morphogen, mediates cholesterol transport across the plasma membrane by harnessing the proton motive force. In cancer, PTCH1 is frequently overexpressed and promotes chemoresistance by transporting drugs such as doxorubicin (dxr) out of cells. Among the inhibitors identified, PAH stands out for its ability to significantly enhance the efficacy of several chemotherapeutic drugs on melanoma and breast cancer cells. To investigate PTCH1s structure in complex with its inhibitor PAH, we overexpressed a construct spanning residues 1-619 and 720-1305 in HEK293 cells. The protein localized to the membrane, and transfected cells exhibited reduced sensitivity to dxr compared to control cells. Additionally, we observed a pH-dependent efflux of dxr, which was reversed by PAH, confirming that the PTCH1 construct used in this study functions as an active drug-efflux pump. In the structure of PTCH1 bound to PAH determined using cryo-electron microscopy, PAH occupies a hydrophobic cavity in an extracellular domain which is normally occupied by cholesterol in other PTCH1 structures, and engages in a key hydrogen bond via one of its hydroxyl groups, a feature previously established as essential for its inhibitory function. These findings not only clarify the molecular basis of PAHs action but also provide a structural roadmap for rational drug design, enabling the development of next-generation inhibitors with enhanced potency.

biochemistry↗

bioRxiv2021

A large disordered region confers a wide spanning volume to vertebrate Suppressor of Fused as shown in a trans-species solution study.

Hedgehog (Hh) pathway inhibition by the conserved protein Suppressor of Fused (SuFu) is crucial to vertebrate development. By constrast, SuFu removal has little effect in drosophila. Previous publications showed that the crystal structures of human and drosophila SuFu consist of two ordered domains that are capable of breathing motions upon ligand binding. However, the crystal structure of human SuFu does not give information about 20 N-terminal residues (IDR1) and an eighty-residue-long disordered region (IDR2) in the C-terminus, whose function is important for the pathway repression. These two IDRs are species-dependent. We studied SuFus structure in solution, both with circular dichroism and small angle X-ray scattering, comparing drosophila, zebrafish and human species, to better understand this considerable difference. Our studies show that, in spite of similar crystal structures restricted to ordered domains, drosophila and vertebrate SuFu have very different structures in solution. The IDR2 of vertebrates spans a large area, thus enabling it to reach for partners and be accessible for post-translational modifications. Furthermore, we show that the IDR2 region is highly conserved within phyla but varies in length and sequence, with insects having a shorter disordered region while that of vertebrates is broad and mobile. This major variation may explain the different phenotypes observed upon SuFu removal.

biophysics↗

bioRxiv2021

Functional and structural characterization of Serratia marcescens ExbB: determinants of the interaction with HasB/TonB

ExbB and ExbD are cytoplasmic membrane proteins that associate with TonB to convey the energy of the proton-motive force to outer membrane receptors in Gram-negative bacteria for iron uptake. The opportunistic pathogen Serratia marcescens (Sm) possesses both TonB and a heme-specific TonB paralog, HasB. ExbBSm has a long periplasmic extension absent in other bacteria such as E. coli (Ec). Long ExbBs are found in several genera of Alphaproteobacteria, most often in correlation with a hasB gene. We investigated specificity determinants of ExbBSm and HasB. We determined the cryo-EM structures of ExbBSm and of the ExbB-ExbDSm complex from S. marcescens. ExbBSm alone is a stable pentamer, and its complex includes two ExbD monomers. We showed that ExbBSm extension interacts with HasB and is involved in heme acquisition and we identified key residues in the membrane domain of ExbBSm and ExbBEc, essential for function and likely involved in the interaction with TonB/HasB. Our results shed light on the new class of inner membrane energy machinery formed by ExbB,ExbD and HasB.

microbiology↗