Hartrampf, N. | Search bioRxiv

bioRxiv2021

Structural Diversity of Photoswitchable Sphingolipids for Optodynamic Control of Lipid Raft Microdomains

Sphingolipids are a structurally diverse class of lipids predominantly found in the plasma membrane of eukaryotic cells. These lipids can laterally segregate with other saturated lipids and cholesterol into lipid rafts; liquid-ordered (Lo) microdomains that act as organizing centers within biomembranes. Owing the vital role of sphingolipids for lipid segregation, controlling their lateral localization is of utmost significance. Hence, we made use of the light-induced trans-cis isomerization of azobenzene-modified acyl chains, to develop a set of photoswitchable sphingolipids, with different headgroups (hydroxyl, galactosyl, phosphocholine) and backbones (sphingosine, phytosphingosine, tetrahydropyran (THP)-blocked sphingosine), able to shuttle between liquid-ordered (Lo) and liquid-disordered (Ld) regions of model membranes upon irradiation with UV-A ({lambda} = 365 nm) and blue ({lambda} = 470 nm) light, respectively. Using combined high-speed atomic force microscopy, fluorescence microscopy, and force spectroscopy, we investigated how these active sphingolipids laterally remodel supported bilayers upon photo-isomerization, notably in terms of domain area changes, height mismatch, line tension, and membrane piercing. Hereby, we show that all sphingosine-(Azo-{beta}-Gal-Cer, Azo-SM, Azo-Cer) and phytosphingosine-based (Azo--Gal-PhCer, Azo-PhCer) photolipids behave similarly, promoting a reduction in Lo domain area when in the UV-adapted cis-isoform. In contrast, azo-sphingolipids having THP groups that block H-bonding at the sphingosine backbone (Azo-THP-SM, Azo-THP-Cer) induce an increase in the Lo domain area when in cis, accompanied by a major rise in height mismatch and line tension. These changes were fully reversible upon blue light-triggered isomerization of the various lipids back to trans, pinpointing the role of interfacial interactions for the formation of stable Lo lipid raft domains.

biophysics↗

bioRxiv2020

BTP-7, a novel peptide for therapeutic targeting of malignant brain tumors

BackgroundTargeted therapies for malignant brain cancer that are currently available have little clinical activity, highlighting an urgent need for the development of novel precision medicines. Brevican (Bcan), a central nervous system (CNS)-specific extracellular matrix protein is upregulated in glioma cells. A brevican isoform lacking glycosylation, dg-Bcan, is a unique glioma marker and thus represents a valuable target for anti-cancer therapy. In this study, we aimed to find a versatile dg-Bcan specific ligand to facilitate glioma targeting. MethodsWe screened a D-peptide library to identify dg-Bcan-Targeting Peptide (BTP) candidates, which were characterized extensively through binding kinetic analyses, cell uptake tests and animal studies. ResultsThe top candidate, BTP-7 binds dg-Bcan with high affinity and specificity, is preferentially internalized by Bcan-expressing glioma cells and can cross the blood-brain barrier in vitro and in mice. Functionalization of camptothecin with BTP-7 led to increased drug delivery to intracranial glioblastoma and cytotoxicity in tumor tissues, as well as prolonged survival in tumor-bearing mice. Conclusiondg-Bcan is an attractive therapeutic target for high-grade gliomas, and BTP-7 represents a promising lead candidate for further development into novel targeted therapeutics. Key pointsO_LIBTP-7 is a high affinity peptide ligand for the dg-Bcan protein and Bcan-expressing cells. C_LIO_LIBTP-7 targets human intracranial GBM xenografts in mice. C_LIO_LIFunctionalization of a toxic anti-cancer drug with BTP-7 enables targeted delivery of the therapeutic to intracranial GBM in mice C_LI Importance of the StudyTargeted therapies for malignant brain cancer that are currently available have little clinical activity, highlighting an urgent need for the development of novel precision medicines that can selectively recognize and kill high-grade glioma tissues. A protein called dg-Bcan is an ideal target because it is present only in the extracellular matrix of high-grade glioma cells and is absent from normal brain tissues. Here, we describe the discovery of a novel dg-Bcan-Targeting Peptide, called BTP-7 that can bind specifically to high-grade glioma cells/tissues, and thus serve as a promising drug delivery vehicle.

bioengineering↗