BJ Articles Ahead of Print

N-methyl D aspartate (NMDA) receptors mediate synaptic excitatory signaling in the mammalian central nervous system by forming calcium-permeable transmembrane channels upon binding glutamate and co-agonist glycine. Ca2+ influx through NMDA receptors leads to channel inactivation through a process mediated by resident calmodulin bound to the intracellular C-terminal segment of the GluN1 subunit of the receptor. Using single molecule FRET investigations, we show that in the presence of calcium-calmodulin the distance across the two GluN1 subunits at the entrance of the first transmembrane segment is shorter, and the bi-lobed cleft of the glycine-binding domain in GluN1 is more closed when bound to glycine and glutamate, relative to what is observed in the presence of barium-calmodulin.

In mammalian cells, extracellular protons act as orthosteric and allosteric ligands for multiple receptors and channels. The aim of this study is to identify proton sensors in the rat pituitary gland. qRT-PCR analysis indicated the expression of G protein-coupled receptor 68 gene (Gpr68) and acid-sensing ion channel (ASIC) genes Asic1, Asic2, and Asic4 in anterior pituitary cells, and Asic1 and Asic2 in immortalized GH3 pituitary cells. Asic1a and Asic2b were the dominant splice isoforms. Single anterior pituitary cell RNA sequencing and immunocytochemical analysis showed that nonexcitable folliculostellate cells express GPR68 gene and protein, whereas excitable secretory cells express ASIC genes/proteins.

With the rapid rate of Covid-19 infections and deaths, treatments and cures besides hand washing, social distancing, masks, isolation, and quarantines are urgently needed. The treatments and vaccines rely on the basic biophysics of the complex viral apparatus. While proteins are serving as main drug and vaccine targets, therapeutic approaches targeting the 30,000 nucleotide RNA viral genome form important complementary approaches. Indeed, the high conservation of the viral genome, its close evolutionary relationship to other viruses, and the rise of gene editing and RNA-based vaccines all argue for a focus on the RNA agent itself.

In sickle cell disease, aberrant blood flow due to oxygen-dependent changes in red cell biomechanics is a key driver of pathology. Most studies to date have focused on the potential role of altered red cell deformability and blood rheology in precipitating vaso-occlusive crises. Numerous studies, however, have shown that sickle blood flow is affected even at high oxygen tensions, suggesting a potentially systemic role for altered blood flow in driving pathologies, including endothelial dysfunction, ischemia, and stroke.

Huntington’s disease (HD) is a heritable neurodegenerative disease that is caused by a CAG expansion in the first exon of the huntingtin gene. This expansion results in an elongated polyglutamine (polyQ) domain that increases the propensity of huntingtin exon-1 (HTTex1) to form cross-β fibrils. While the polyQ domain is important for fibril formation, the dynamic, C-terminal proline-rich domain (PRD) of HTTex1 makes up a large fraction of the fibril surface. Because potential fibril toxicity has to be mediated by interactions of the fibril surface with its cellular environment, we wanted to model the conformational space adopted by the PRD.

Single molecule Förster Resonance Energy Transfer (smFRET) is a powerful technique for investigating the structural dynamics of biological macromolecules. smFRET reveals the conformational landscape and dynamic changes of proteins by building on the static structures found using cryo-electron microscopy, x-ray crystallography, and other methods. Combining smFRET with static structures allows for a direct correlation between dynamic conformation and function. Here we discuss the different experimental setups, fluorescence detection schemes, and data analysis strategies that enable the study of structural dynamics of glutamate signaling across various timescales.

Asymmetric dimer formation of epidermal growth factor receptor (EGFR) is crucial for EGF-induced receptor activation. Even though autophosphorylation is important for activation, its role remains elusive in the context of regulating dimers. In this study, employing overlapping time-series analysis to raster image correlation spectroscopy (RICS) we observed time dependent transient dynamics of EGFR dimerization and found EGFR kinase activity to be essential for dimerization. As a result of which, we hypothesized that phosphorylation could influence dimerization.

The cell nucleus is a compartment in which essential processes such as gene transcription and DNA replication occur. While the large amount of chromatin confined in the finite nuclear space could install the picture of a particularly dense organelle surrounded by less dense cytoplasm, recent studies have begun to report the opposite. However, the generality of this newly emerging, opposite picture has so far not been tested. Here, we used combined optical diffraction tomography (ODT) and epi-fluorescence microscopy to systematically quantify the mass densities of cytoplasm, nucleoplasm, and nucleoli of human cell lines, challenged by various perturbations.

Gene regulation by control of transcription initiation is a fundamental property of living cells. Much of our understanding of gene repression originated from studies of the E. coli lac operon switch, where DNA looping plays an essential role. To validate and generalize principles from lac for practical applications, we previously described artificial DNA looping driven by designed Transcription Activator-Like Effector Dimer (TALED) proteins. Because TALE monomers bind the idealized symmetrical lac operator sequence in two orientations, our prior studies detected repression due to multiple DNA loops.

The motility of microalgae has been studied extensively, particularly in model microorganisms such as Chlamydomonas reinhardtii. For this and other microalgal species, diurnal cycles are well-known to control the metabolism, growth and cell division. Diurnal variations, however, have been largely neglected in quantitative studies of motility. Here, we demonstrate using tracking microscopy how the motility statistics of C. reinhardtii are modulated by diurnal cycles. With nine independently innoculated cultures synchronized to the light-dark cycle at the exponential growth phase, we repeatedly observed that the mean swimming speed is greater during the dark period of a diurnal cycle.

During amyloidogenesis, proteins undergo conformational changes that allow them to aggregate and assemble into insoluble, fibrillar structures. Soluble oligomers that form during this process typically contain 2-24 monomeric subunits and are cytotoxic. Prior to the formation of these soluble oligomers, monomeric species first adopt aggregation-competent conformations. Knowledge of the structures of these intermediate states is invaluable to the development of molecular strategies to arrest pathological amyloid aggregation.