Lipid droplets form a network interconnected by the endoplasmic reticulum through which they equilibrate their proteins

Lipid droplets (LDs) are globular intracellular structures dedicated to the storage of neutral lipids. They are closely associated with the endoplasmic reticulum (ER) and are delineated by a monolayer of phospholipids that is continuous with the cytoplasmic leaflet of the ER membrane. LDs contain a specific set of proteins, but how these proteins are targeted to the LD surface is not fully understood. Here we devised a yeast mating-based microscopic readout to monitor the transfer of LD proteins upon zygote formation. The results of this analysis indicate that ER fusion between mating partners is required for transfer of LD proteins and that this transfer is continuous, bidirectional and affects most LDs simultaneously. These observations suggest that LDs do not fuse upon mating of yeast cells, but that they form a network that is interconnected through the ER membrane. Consistent with this, ER-localized LD proteins rapidly move onto LDs of a mating partner and this protein transfer is affected by seipin, a protein important for proper LD biogenesis and the functional connection of LDs with the ER membrane.

Protein Transfer through an F Plasmid-Encoded Type IV Secretion System Suppresses the Mating-Induced SOS Response

Many bacteria carry plasmids and other mobile genetic elements (MGEs) whose conjugative transfer through encoded type IV secretion systems (T4SSs), or “mating channels,” can lead to a rapid intra- and interspecies proliferation of genes encoding resistance to antibiotics or heavy metals or virulence traits. Here, we show that a model IncF plasmid-encoded T4SS translocates not only DNA but also several proteins intercellularly.

Protein transfer learning improves identification of heat shock protein families

Heat shock proteins (HSPs) play a pivotal role as molecular chaperones against unfavorable conditions. Although HSPs are of great importance, their computational identification remains a significant challenge. Previous studies have two major limitations. First, they relied heavily on amino acid composition features, which inevitably limited their prediction performance. Second, their prediction performance was overestimated because of the independent two-stage evaluations and train-test data redundancy. To overcome these limitations, we introduce two novel deep learning algorithms: (1) time-efficient DeepHSP and (2) high-performance DeeperHSP. We propose a convolutional neural network (CNN)-based DeepHSP that classifies both non-HSPs and six HSP families simultaneously. It outperforms state-of-the-art algorithms, despite taking 14–15 times less time for both training and inference. We further improve the performance of DeepHSP by taking advantage of protein transfer learning. While DeepHSP is trained on raw protein sequences, DeeperHSP is trained on top of pre-trained protein representations. Therefore, DeeperHSP remarkably outperforms state-of-the-art algorithms increasing F1 scores in both cross-validation and independent test experiments by 20% and 10%, respectively. We envision that the proposed algorithms can provide a proteome-wide prediction of HSPs and help in various downstream analyses for pathology and clinical research.

Effect of Brine Calcium Concentration on the Surface Solubilization and Texture of Fresh Perline Mozzarella Cheese

Softening of cheese surface is a common problem especially in brined cheeses. In this study, the effects of the brine calcium concentrations on the texture of fresh perline Mozzarella cheese were investigated. The compositions of cheeses were analyzed 2 weeks after production. Brine protein content were monitored at 2 and 4 week of storage. The effect of the brine calcium concentration on the texture and meltability of cheeses were monitored Texture Profile Analysis (TPA) and Schreiber meltability test at 2 and 4 weeks of storage. The decrease in brine calcium concentration increased the protein transfer from cheese to brine, leading to an increase in the moisture content of cheese. As the calcium concentration increased in brine, an increase in the hardness, and decrease in adhesiveness and meltability of the cheeses were observed during storage. In conclusion, softening/solubilization of the surface of fresh perline Mozzarella cheese can be prevented with increasing the brine calcium concentration.

Prisoners receive food fit for a queen: honeybees feed small hive beetles protein-rich glandular secretions through trophallaxis

The honeybee nest parasite Aethina tumida (small hive beetle), uses behavioural mimicry to induce trophallactic feeding from its honeybee hosts. Small hive beetles are able to induce honeybee workers to share the carbohydrate–rich contents of their crops, but it is not clear whether the beetles are able to induce to workers to feed them the protein-rich hypopharyngeal glandular secretions fed to the queen, larvae and other nest mates. Protein is a limiting macronutrient in an insect's diet, essential for survival, growth and fecundity. Honeybees obtain protein from pollen, which is consumed and digested by nurse bees. They then distribute the protein to the rest of the colony in the form of hypopharyngeal gland secretions. Using 14C-phenylalanine as a qualitative marker for protein transfer, we show that small hive beetles successfully induce worker bees to feed them the protein-rich secretions of their hypopharyngeal glands during trophallaxis, and that females are more successful than males in inducing the transfer of these protein-rich secretions. Furthermore, behavioural observations demonstrated that female beetles do not preferentially interact with a specific age cohort of bees when soliciting food, but males tend to be more discriminate and avoids the more aggressive and active older bees.

Tasmanian devil CD28 and CTLA4 capture CD80 and CD86 from adjacent cells

Immune checkpoint immunotherapy is a pillar of human oncology treatment with potential for non-human species. The first checkpoint immunotherapy approved for human cancers targeted the CTLA4 protein. CTLA4 can inhibit T cell activation by capturing and internalizing CD80 and CD86 from antigen presenting cells, a process called trans-endocytosis. Similarly, CD28 can capture CD80 and CD86 via trogocytosis and retain the captured ligands on the surface of the CD28-expressing cells. The wild Tasmanian devil (Sarcophilus harrisii) population has declined by 77% due to transmissible cancers that evade immune defenses despite genetic mismatches between the host and tumours. We used a live cell-based assay to demonstrate that devil CTLA4 and CD28 can capture CD80 and CD86. Mutation of evolutionarily conserved motifs in CTLA4 altered functional interactions with CD80 and CD86 in accordance with patterns observed in other species. These results suggest that checkpoint immunotherapies can be translated to evolutionarily divergent species.HighlightsKey immune checkpoint receptor-ligand interactions are conserved in marsupials.Live cell-based assays show Tasmanian devil CD28 and CTLA4 can capture CD80 and CD86 in trans from adjacent cells.Mutation of the conserved CTLA4MYPPPY ligand binding motif to CTLA4MYPPPA reduces binding to CD80 and intercellular protein transfer.Removal of conserved CTLA4YVKM protein recycling binding motif in CTLA4 results in bidirectional intercellular protein transfer between CTLA4 and CD80.Highly successful human immune checkpoint immunotherapies have the potential to be translated for veterinary and conservation medicine.