Augmenting the cytotoxicity of oleic acid-protein complexes: Potential of target-specific antibodies

The mosquito protein AEG12 displays both cytolytic and antiviral properties via a common lipid transfer mechanism

The mosquito protein AEG12 is up-regulated in response to blood meals and flavivirus infection though its function remained elusive. Here, we determine the three-dimensional structure of AEG12 and describe the binding specificity of acyl-chain ligands within its large central hydrophobic cavity. We show that AEG12 displays hemolytic and cytolytic activity by selectively delivering unsaturated fatty acid cargoes into phosphatidylcholine-rich lipid bilayers. This property of AEG12 also enables it to inhibit replication of enveloped viruses such as Dengue and Zika viruses at low micromolar concentrations. Weaker inhibition was observed against more distantly related coronaviruses and lentivirus, while no inhibition was observed against the nonenveloped virus adeno-associated virus. Together, our results uncover the mechanistic understanding of AEG12 function and provide the necessary implications for its use as a broad-spectrum therapeutic against cellular and viral targets.

Using BAMLET complex in a functional spreadable cheese elaborated with bovine colostrum

BAMLET is a bioactive complex formed by the interaction between α-Lactoalbumin (α-LA) and oleic acid which exhibits cytotoxic activity against cancer cells. BAMLET is selectively cytotoxic to malignant cells while sparing the healthy ones. There are, however, no reports about its application in a food matrix. The objective of this work was to synthetize the BAMLET complex from oleic acid and bovine colostrum from the second and third milkings which naturally contain α-LA to prepare two functional spreadable cheeses. The complex was successfully formed and retained in the cheeses as verified through SDS-PAGE applied to the whey obtained. The spreadable cheese from the second milking had a higher protein content (13.56 ± 0.02%) and a higher yield (40%) than the product obtained from the third milking. Even though the cheeses did not show any significant differences (p > 0.05) in the inhibition of the angiotensin-converting enzyme 1, their inhibitory activities were good, as a 0.5 g portion of the cheese from the second milking was sufficient to inhibit 57.52 ± 9.17%, while the cheese from the third milking inhibited 51.48 ± 1.07% of the enzyme. The sensory analysis showed a good acceptance for both spreadable cheeses.

Structures and mechanisms of formation of liprotides

Many proteins form complexes called liprotides with oleic acid and other cis-fatty acids under conditions where the protein is partially unfolded. The complexes vary in structure depending on the ratio of protein and lipid, but the most common structural organization is the core-shell structure, in which a layer of dynamic, partially unfolded and extended proteins surrounds a micelle-like fatty acid core. This structure, first reported for α-lactalbumin together with OA, resembles complexes formed between proteins and anionic surfactants like SDS. Liprotides first rose to fame through their anti-carcinogenic properties which still remains promising for topical applications though not yet implemented in the clinic. In addition, liprotides show potential in drug delivery thanks to the ability of the micelle core to solubilize and stabilize hydrophobic compounds, though applications are challenged by their sensitivity to acidic pH and dynamic exchange of lipids which makes them easy prey for serum "hoovers" such as albumin. However, liprotides are also of fundamental interest as a generic "protein complex structure", demonstrating the many and varied structural consequences of protein-lipid interactions. Here we provide an overview of the different types of liprotide complexes, ranging from quasi-native complexes via core-shell structures to multi-layer structures, and discuss the many conditions under which they form. Given the many variable types of complexes that can form, rigorous biophysical analysis (stoichiometry, shape and structure of the complexes) remains crucial for a complete understanding of the mechanisms of action of this fascinating group of protein-lipid complexes both in vitro and in vivo.