BJ Articles Ahead of Print

First proposed as a specialized mode of release at sensory neurons possessing ribbon synapses, multivesicular release has since been described throughout the CNS. Many aspects of multivesicular release remain poorly understood. We explored mechanisms underlying simultaneous multivesicular release at ribbon synapses in salamander retinal rod photoreceptors. We assessed spontaneous release presynaptically by recording glutamate transporter anion currents (IA(glu)) in rods. Spontaneous IA(glu) events were correlated in amplitude and kinetics with simultaneously measured miniature excitatory post-synaptic currents (mEPSCs) in horizontal cells.

Raster image correlation spectroscopy (RICS) is a fluorescence image analysis method for extracting the mobility, concentration and stoichiometry of diffusing fluorescent molecules from confocal image stacks. The method works by calculating a spatial correlation function for each image and analyzing the average of those by model fitting. Rules of thumb exist for RICS image acquisitioning, yet a rigorous theoretical approach to predict the accuracy and precision of the recovered parameters has been lacking.

Membrane protein functions can be altered by subtle changes in the host lipid bilayer physical properties. Gramicidin channels have emerged as a powerful system for elucidating the underlying mechanisms of membrane protein function regulation through changes in bilayer properties, which is reflected in the thermodynamic equilibrium distribution between nonconducting gramicidin monomers and conducting bilayer-spanning dimers. To improve our understanding of how subtle changes in bilayer thickness alter the gramicidin monomer and dimer distributions, we performed extensive atomistic molecular dynamics (MD) simulations and fluorescence quenching experiments on gramicidin A (gA).

Motor proteins are biological machines that convert chemical energy stored in ATP to mechanical work. Kinesin and dynein are microtubule (MT) associated motor proteins that, among other functions, facilitate intracellular transport. Here, we focus on dynein motility. We deduce the directional step distribution of yeast dynein motor protein on the MT surface by combing intrinsic features of the dynein and MT. These include the probability distribution of the separation vector between the two microtubule binding domains (MTBDs), the angular probability distribution of a single MTBD translation, the existence of a MT seam defect, MT binding sites, and theoretical extension that accounts for a load force on the motor.

Peripheral membrane proteins with intrinsic curvature can act both as sensors of membrane curvature and shape modulators of the underlying membranes. A well-studied example of such proteins is the mechano-chemical GTPase dynamin that assembles into helical filaments around membrane tubes and catalyzes their scission in a GTPase-dependent manner. It is known that the dynamin coat alone, without GTP, can constrict membrane tubes to radii of about 10 nanometers, indicating that the intrinsic shape and elasticity of dynamin filaments should play an important role in membrane remodeling.

Dendritic spines are the primary excitatory postsynaptic sites that act as subcompartments of signaling. Ca2+ is often the first and most rapid signal in spines. Downstream of calcium, the cAMP/PKA pathway plays a critical role in the regulation of spine formation, morphological modifications, and ultimately, learning and memory. While the dynamics of calcium are reasonably well-studied, calcium-induced cAMP/PKA dynamics, particularly with respect to frequency modulation, are not fully explored.

Dendritic spines are the primary excitatory postsynaptic sites that act as subcompartments of signaling. Ca2+ is often the first and most rapid signal in spines. Downstream of calcium, the cAMP/PKA pathway plays a critical role in the regulation of spine formation, morphological modifications, and ultimately, learning and memory. While the dynamics of calcium are reasonably well-studied, calcium-induced cAMP/PKA dynamics, particularly with respect to frequency modulation, are not fully explored.

In allosteric proteins, binding a ligand can affect function at a distant location, for example by changing the binding affinity of a substrate at the active site. The induced fit and population shift models, which differ by the assumed number of stable configurations, explain such cooperative binding from a thermodynamic viewpoint. Yet, understanding what mechanical principles constrain these models remains a challenge. Here we provide an empirical study on 34 proteins supporting the idea that allosteric conformational change generally occurs along a soft elastic mode presenting extended regions of high shear.

Dimerization or the formation of higher-order oligomers is required for the activation of ErbB receptor tyrosine kinases. The heregulin receptor, ErbB3, must heterodimerize with other members of the family, preferentially ErbB2, to form a functional signal transducing complex. Here, we applied single molecule imaging capable of detecting long-lived and mobile associations to measure their stoichiometry and mobility, and analyzed data from experiments globally taking the different lateral mobility of monomeric and dimeric molecular species into account.

Cardiac electrical excitation-propagation is influenced by myocyte orientations (cellular organisation). Quantitatively understanding this relationship presents a significant research challenge, especially during arrhythmias where excitation patterns become complex. Tissue-scale simulations of cardiac electrophysiology, incorporating both dynamic action potential (AP) behaviour and image-based myocardial architecture, provide an approach to investigate three-dimensional (3D) propagation of excitation waves in the heart.

The clustered regularly interspaced short palindromic repeats (CRISPR) system, an immune system analog found in prokaryotes, allows a single guide RNA (sgRNA) to direct a CRISPR-associated protein (Cas) with combined helicase and nuclease activity to DNA. The presence of a specific Protospacer Adjacent Motif (PAM) next to the DNA target site plays a crucial role in determining both efficacy and specificity of gene editing. Herein we introduce a coevolutionary framework to computationally unveil non-obvious molecular interactions in CRISPR systems and experimentally probe their functional role.