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Biology subjects

Sasset, L.

Publications and source records attributed to Sasset, L..

3 recordsLinked to original sources

DNA-based delivery of incretin receptor agonists using MYO Technology leads to durable weight loss in a diet-induced obesity model

Therapeutic proteins have seen a substantial increase in clinical development and use across many disease areas. Despite their broad applicability, significant drawbacks limit access to many of these drugs, including: i) high manufacturing costs; ii) administration via time-consuming infusions; iii) frequent dosing, sometimes even daily; and iv) requirements for low temperature storage. MYO Technology was developed to overcome these barriers. The MYO Technology platform consists of therapeutic-encoding plasmid DNA (pDNA), and a proprietary medical device for intramuscular injection and delivery of electrical pulses. These pulses enable the in vivo electroporation of muscle cells and uptake of injected pDNA, leading to the production, secretion, and delivery of the therapeutic protein into peripheral circulation. MYO Technology offers several advantages over standard delivery of therapeutic proteins; pDNA manufacturing is a simpler and less specialized process compared to protein manufacturing, and pDNA is very stable and lacks most cold chain requirements. Furthermore, administration using MYO Technology takes only a few minutes, and the serum level of a therapeutic protein can potentially be maintained for many months without the need for redosing. Incretin receptor agonists (IRAs) are a class of therapeutic proteins that have recently come to prominence as powerful weight and glucose control drugs, and are used for the treatment of type 2 diabetes (T2D) and obesity. Semaglutide and tirzepatide, currently the most widely used within this class, are both potent molecules, but have a short half-life, requiring weekly administration by subcutaneous injections. Moreover, since their clinical benefits rapidly disappear upon treatment cessation, T2D and obese patients may have a life-long dependency on IRAs, and the requirement for weekly injections can negatively affect the quality of life and the adherence to therapy, as well as create a significant financial burden. Therefore, increasing the interval between injections has become one of the major goals in the field. Here, we present our preclinical studies on the delivery of IRAs with MYO Technology. Animal proof-of-concept studies demonstrate that MYO Technology-delivered IRAs are functional, and efficacious in promoting long-lasting weight and glucose control in mouse models of diet-induced obesity. Moreover, engineering the IRAs to facilitate blood-brain barrier penetration further enhances treatment efficacy, with benefits persisting beyond one year following a single administration. Together, these findings highlight MYO Technologys potential to transform care for patients with T2D and obesity by enabling long-lasting therapeutic effects with minimal dosing, ultimately improving quality of life and treatment adherence.

physiology↗

S1P controls endothelial sphingolipid homeostasis via ORMDL

Sphingolipids (SL) are both membrane building blocks and potent signaling molecules regulating a variety of cellular functions in both physiological and pathological conditions. Under normal physiology, sphingolipid levels are tightly regulated, whereas disruption of sphingolipid homeostasis and signaling has been implicated in diabetes, cancer, cardiovascular and autoimmune diseases. Yet, mechanisms governing cellular sensing of SL, and according regulation of their biosynthesis remain largely unknown. In yeast, serine palmitoyltransferase (SPT), catalyzing the first and rate limiting step of sphingolipid de novo biosynthesis, is negatively regulated by Orosomucoid 1 and 2 (Orm) proteins. Lowering sphingolipid levels triggers Orms phosphorylation, resulting in the removal of the inhibitory brake on SPT to enhance sphingolipid de novo biosynthesis. However, mammalian orthologs ORMDLs lack the N-terminus hosting the phosphosites. Thus, which sphingolipid(s) are sensed by the cells, and mechanisms of homeostasis remain largely unknown. This study is aimed at filling this knowledge gap. Here, we identify sphingosine-1-phosphate (S1P) as the key sphingolipid sensed by endothelial cells via S1PRs. The increase of S1P-S1PR signaling stabilizes ORMDLs, which downregulates SPT activity to maintain SL homeostasis. These findings reveal the S1PR/ORMDLs axis as the sensor-effector unit regulating SPT activity accordingly. Mechanistically, the hydroxylation of ORMDLs at Pro137 allows a constitutive degradation of ORMDLs via ubiquitin-proteasome pathway, therefore preserving SPT activity at steady state. The disruption of the S1PR/ORMDL axis results in ceramide accrual, mitochondrial dysfunction, and impaired signal transduction, all leading to endothelial dysfunction, which is an early event in the onset of cardio- and cerebrovascular diseases. The disruption of S1P-ORMDL-SPT signaling may be implicated in the pathogenesis of conditions such as diabetes, cancer, cardiometabolic disorders, and neurodegeneration, all characterized by deranged sphingolipid metabolism. Our discovery may provide the molecular basis for a therapeutic intervention to restore sphingolipid homeostasis.

cell biology↗

Cryo-EM structures reveal bilayer remodeling during Ca2+ activation of a TMEM16 scramblase

The lipid distribution of plasma membranes of eukaryotic cells is asymmetric and phospholipid scramblases disrupt this asymmetry by mediating the rapid nonselective transport of lipids down their concentration gradients. As a result, phosphatidylserine is exposed to the outer leaflet of membrane, an important step in extracellular signaling networks controlling processes such as apoptosis, blood coagulation, membrane fusion and repair. Several members of the TMEM16 family have been identified as Ca2+-activated scramblases but the mechanisms underlying their Ca2+-dependent gating and their effects on the surrounding lipid bilayer remain poorly understood. Here we describe three high-resolution cryo-electron microscopy structures of a fungal scramblase from Aspergillus fumigatus, afTMEM16, reconstituted in lipid nanodiscs, revealing large Ca2+-dependent conformational changes of the protein as well as significant, function dependent membrane reorganization.

biochemistry↗