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Microtubules (MTs) constitute the largest components of the eukaryotic cytoskeleton and play crucial roles in various cellular processes, including mitosis and intracellular transport. The property allowing MTs to cater to such diverse roles is attributed to dynamic instability, which is coupled to the hydrolysis of GTP (guanosine-5'-triphosphate) to GDP (guanosine-5'-diphosphate) within the β-tubulin monomers. Understanding the equilibrium dynamics and the structural features of both GDP- and GTP-complexed MT tips, especially at an all-atom level, remains challenging for both experimental and computational methods because of their dynamic nature and the prohibitive computational demands of simulating large, many-protein systems.

In every heartbeat, cardiac muscle cells perform excitation-Ca2+ signaling-contraction (EC) coupling to pump blood against the vascular resistance. Cardiomyocytes can sense the mechanical load and activate mechano-chemo-transduction (MCT) mechanism, which provides feedback regulation of EC coupling. MCT feedback is important for the heart to upregulate contraction in response to increased load to maintain cardiac output. MCT feedback enhances the L-type Ca2+ current, sensitizes ryanodine receptors (RyRs), and augments SERCA pump activity, thereby maintaining contraction amplitude despite increased load.

In this work we present a minimal structure-based model of protein diffusional search along local DNA amid protein binding and unbinding events on the DNA, taking into account protein-DNA electrostatic interactions and hydrogen-bonding (HB) interactions or contacts at the interface. We accordingly constructed the protein diffusion-association/dissociation free energy surface and mapped it to 1D as the protein slides along DNA, maintaining the protein-DNA interfacial HB contacts that presumably dictate the DNA sequence information detection.

Dense-core vesicles (DCVs) are found in various types of cells, such as neurons, pancreatic β-cells, and chromaffin cells. These vesicles release transmitters, peptides, and hormones to regulate diverse functions, such as the stress response, immune response, behavior, and blood glucose levels. In traditional electron microscopy after chemical fixation, it is often reported that the dense cores occupy a portion of the vesicle towards the center and are surrounded by a clear halo. With electron microscopy following cryo-fixation in adrenal chromaffin cells, we report here that we did not observe halos, but dense cores filling up the entire vesicles suggesting that halos are likely the product of chemical fixation.

Neuropeptides are inter-cellular signaling molecules occurring throughout animals. Most neuropeptides bind and activate G-protein coupled receptors, but some also activate ionotropic receptors (or “ligand-gated ion channels”). This is exemplified by the tetra-peptide H-Phe-Met-Arg-Phe-NH2 (FMRFa), which activates mollusc and annelid FMRFa-gated sodium channels (FaNaCs) from the trimeric degenerin/epithelial sodium channel superfamily. Here, we explored the structure-activity relationships determining FMRFa potency at mollusc and annelid FaNaCs in the light of emerging structural data, using synthetic neuropeptide analogues, heterologous expression, and two-electrode voltage clamp.

Stretch activation (SA), a delayed increase in force production following rapid muscle lengthening, is critical to the function of vertebrate cardiac muscle and insect asynchronous indirect flight muscle (IFM). SA enables or increases power generation in muscle types used in a cyclical manner. Recently, myosin isoform expression has been implicated as a mechanism for varying the amplitude of SA in some muscle types. For instance, we found that expressing a larval Drosophila myosin isoform in a muscle type with minimal SA, the Drosophila jump muscle, substantially increased SA amplitude and enabled positive cyclical power generation.

Binuclear ruthenium complexes have been investigated for potential DNA-targeted therapeutic and diagnostic applications. Studies of DNA threading intercalation, in which DNA base pairs must be broken for intercalation, have revealed means of optimizing a model binuclear ruthenium complex to obtain reversible DNA-ligand assemblies with the desired properties of high affinity and slow kinetics. Here, we used single-molecule force spectroscopy to study a binuclear ruthenium complex with a longer semi-rigid linker relative to the model complex.

Migrasomes, the vesicle-like membrane micro-structures, arise on the retraction fibers (RFs), the branched nano-tubules pulled out of cell plasma membranes during cell migration and shaped by membrane tension. Migrasomes form in two steps: a local RF bulging is followed by a protein-dependent stabilization of the emerging spherical bulge. Here we addressed theoretically and experimentally the previously unexplored mechanism of bulging of membrane tubular systems. We assumed that the bulging could be driven by increases in membrane tension and experimentally verified this hypothesis in live cell and biomimetic systems.

Statement of significance – In this paper, we show a surprising connection between hypo-osmotic stress and circadian rhythm which may be rooted in part by caveolae domains in the cell membrane.

STATEMENT OF SIGNIFICANCE: Soluble N-ethylmaleimide Sensitive Factor Attachment Protein Receptor (SNARE) proteins catalyze membrane fusion, including the exquisitely coordinated fusion between vesicles and the plasma membrane required for synaptic neurotransmission. The core presynaptic SNARE machinery is a four-helix heterotrimer that includes SNAP25, a protein of unique topology that contributes two SNARE motif helices to the final complex. This work investigates the intrinsic properties of each SNAP25 SNARE motif and their contribution to SNARE assembly and fusion in model membranes. Unexpected and strikingly distinct functional characteristics of the individual domains in a membrane environment are described that provide evidence for a new level of intra-protein regulation that contributes to the highly specialized fusion mechanism of presynaptic neuronal SNAREs.