Biology subjects

Lan, L.

Publications and source records attributed to Lan, L..

22 records · Page 2Linked to original sources

bioRxiv2020

Mechanism of RNA recognition by a Musashi RNA-binding protein

The Musashi RNA-binding proteins (RBPs) regulate translation of target mRNAs and maintenance of cell stemness and tumorigenesis. Musashi-1 (MSI1), long considered as an intestinal and neural stem cell marker, has been more recently found to be overexpressed in many cancers. It has served as an important drug target for treating acute myeloid leukemia and solid tumors such as ovarian, colorectal and bladder cancer. One of the reported binding targets of MSI1 is Numb, a negative regulator of the Notch signaling. However, the dynamic mechanism of Numb RNA binding to MSI1 remains unknown, largely hindering effective drug design targeting this critical interaction. Here, we have performed all-atom simulations using a robust Gaussian accelerated molecular dynamics (GaMD) method, which successfully captured spontaneous and highly accurate binding of the Numb RNA from bulk solvent to the MSI1 protein target site. GaMD simulations revealed that Numb binding to MSI1 involved largely induced fit in both the RNA and protein. The simulations also identified important low-energy intermediate conformational states during RNA binding, in which Numb interacted mainly with the {beta}2-{beta}3 loop and C terminus of MSI1. The mechanistic understanding of RNA binding obtained from our GaMD simulations is expected to facilitate rational structure-based drug design targeting MSI1 and other RBPs.

biophysics↗

bioRxiv2020

A novel copper-sensing two-component system for activating Dsb genes in bacteria

Copper is an essential element for biological systems but becomes toxic when present in excess. In Pseudomonas aeruginosa, an important human pathogen, the resistance to copper requires the induction of dsbDEG operon encoding proteins involved in disulfide-bond formation (Dsb). However, it is unknown how the copper stress induces the transcription of the operon. Here, we report that the exogenous copper induces the transcription of the dsbDEG operon through a new copper-sensing two-component system named DsbRS. The dsbRS is divergently transcribed from the dsbDEG operon, and the response regulator DsbR binds to the intergenic region between the operons. In the absence of copper, the sensor kinase DsbS acts as a phosphatase toward DsbR and thus blocks the transcription of the operons. However, in the presence of copper, the metal ion directly binds to the sensor domain of DsbS, for which the Cys82 residue plays a critical role. The copper-binding appears to inhibit the phosphatase activity of DsbS, leading to activation of DsbR. The copper resistance of the dsbRS knock-out mutant was restored by ectopic expression of the dsbDEG operon, confirming the critical role of the operon in the resistance to copper. Strikingly, cognates of dsbRS-dsbDEG pair are widely distributed across eubacteria. Also, a DsbR-binding site, which contains the consensus sequence 5-TAA-N7-TTAAT-3, is detected in the promoter region of dsbDEG homologs in those species. Thus, regulation of Dsb genes by DsbRS represents a novel mechanism by which bacterial cells cope with copper stress. ImportanceCopper is an essential redox active cofactor that becomes highly cytotoxic when present in excess. Therefore, in order to evade copper toxicity, bacteria must perceive copper stress and tightly regulate genes expression. In the present study, we identify a new copper-sensing two-component system (designated DsbRS) in Pseudomonas aeruginosa, an important human pathogen. We provide multiple lines of evidence that upon copper binding to the periplasmic domain of DsbS, its phosphatase activity is blocked, and the phosphorylated DsbR directly activates the transcription of a number of copper-induced genes including those involved in protein disulfide-bond formation (Dsb). This study suggests that regulation of Dsb genes by DsbRS may be an underappreciated regulatory mechanism by which bacteria sense and respond to copper.

microbiology↗

bioRxiv2019

RNA-Binding Proteins MSI-1 (Musashi) and EXC-7 (HuR) Regulate Serotonin-Mediated Behaviors in C. elegans

The evolutionarily conserved RNA-binding proteins HuR and MSI are essential for multiple developmental processes and are upregulated in many cancer tissues. The C. elegans homologues EXC-7 (HuR) and MSI-1 (MSI1 and MSI2) have been implicated in tubulogenesis, neural development, and specific behaviors that include male tail-curling to maintain contact with the hermaphrodite during mating. This behavior is mediated by serotonin signaling. Here, drug studies plus biochemical and genetic results indicate that MSI-1 affects serotonergic signaling through stabilization of mRNA of the G protein GOA-1/GNAO1 in neurons, which in turn affects activity of the serotonin synthase TPH-1/tryptophan hydroxylase via the response element CRH-1/CREB. EXC-7 (HuR) is also involved in this regulatory pathway. These results indicate a novel pathway and role for these RNA-binding proteins in regulating neurotransmitter levels that could be conserved in other tissues where these RNA-binding proteins are present.\n\nImpact Statement\n\nRNA-binding proteins Musashi and HuR upregulate serotonin levels for male-specific movement during mating via a novel pathway involving a neural G protein, response element, and serotonin synthase.

cell biology↗

bioRxiv2018

Optoacoustic brains stimulation at submillimeter spatial precision

Low-intensity ultrasound is an emerging modality for neuromodulation. Yet, piezo-based transducers offer poor spatial confinement of excitation volume, often bigger than a few millimeters in diameter. In addition, the bulky size limits their implementation in a wearable setting and prevents integration with other experimental modalities. Here, we report spatially confined optoacoustic neural stimulation through a novel miniaturized Fiber-Optoacoustic Converter (FOC). The FOC has a diameter of 600 m and generates omnidirectional ultrasound wave locally at the fiber tip through the optoacoustic effect. We show that the optoacoustic wave can directly activate individual cultured neurons and generate intracellular Ca2+ transients. The FOC activates neurons within a radius of 500 m around the fiber tip, delivering superior spatial resolution over conventional piezo-based low-frequency transducers. Combining FOC with electrophysiology, direct and spatially confined neural stimulation of mouse brain is achieved in vivo.

neuroscience↗