Biology subjects

Tjahjono, N.

Publications and source records attributed to Tjahjono, N..

4 recordsLinked to original sources

bioRxiv2026

Magnetogenetic control of endogenous calcium signaling via ROS-sensitive ion channels reveals astrocytic regulation of neural circuit activity

Astrocytes exhibit complex calcium signaling proposed to detect, integrate, and modulate neuronal activity; however, their causal contribution to neural circuit function remains unresolved. This is partly due to the lack of tools that recapitulate physiological astrocyte calcium signaling. Here, we show that experimental magnetic control of endogenous calcium signaling in astrocytes is sufficient to modulate neural circuit dynamics. Using pmFeRIC, a magnetogenetic tool for remote, noninvasive, and on-demand activation of endogenous calcium pathways, we demonstrate that selective activation of astrocyte calcium signaling drives neuronal activity. pmFeRIC uses magnetic fields and endogenous ferritin to generate localized reactive oxygen species (ROS) at the plasma membrane, activating native ROS-sensitive ion channels, inducing calcium influx. In hippocampal circuits in vitro, magnetic activation of endogenous astrocytic calcium signaling produced robust, state-dependent changes in neuronal circuit activity, in part by increasing presynaptic release probability, postsynaptic burst firing, and glutamatergic transmission. These effects were mediated by transient receptor potential channels, amplified by intracellular calcium stores, and abolished when astrocyte calcium signaling was disrupted, establishing a causal role in neural circuit dynamics. In vivo, pmFeRIC activates endogenous calcium signaling in astrocytes with kinetics comparable to locomotion-induced activity, enabling control of astrocyte calcium dynamics that resemble physiological behavioral responses. Together, these findings establish that endogenous astrocytic calcium signaling is sufficient to modulate neural circuit function and introduce a broadly applicable platform for cell-specific, wireless, on-demand control of endogenous calcium signaling through magnetic activation of ROS-sensitive ion channels.

neuroscience↗

bioRxiv2020

Augmentation of Antibacterial Activity in Mesenchymal Stromal Cells Through Systems-Level Analysis and CRISPR-mediated Activation of CD14

Mesenchymal stromal cells (MSCs) have broad-ranging therapeutic capabilities, however MSC use is confounded by cell-to-cell heterogeneity, and source-to-source phenotypic inconsistencies. We utilized a systems-based approach to compare MSCs which displayed different capacity for antibacterial activity. Although MSCs from both sources satisfied traditional MSC-defining criteria, comparative transcriptomics and quantitative membrane proteomics demonstrated two unique molecular profiles. The antibacterial MSCs respond rapidly to bacterial lipopolysaccharide (LPS) and have elevated levels of the LPS co-receptor CD14. CRISPR-mediated overexpression of endogenous CD14 in non-antibacterial MSCs resulted in faster LPS response and enhanced antimicrobial activity. Single-cell transcriptome profiling of CD14-activated MSCs revealed uniform enhancement of LPS response kinetics, and a shift in the ground state of these MSCs. Our results demonstrate that systems-level analysis can reveal critical molecular targets to optimize desirable properties in MSCs, and that overexpression of CD14 in these cells can shift their state to be more responsive to future bacterial challenge.

molecular biology↗

bioRxiv2020

Engineering high-yield biopolymer secretion creates an extracellular protein matrix for living materials

The bacterial extracellular matrix forms autonomously, giving rise to complex material properties and multicellular behaviors. Synthetic matrix analogues can replicate these functions, but require exogenously added material or have limited programmability. Here we design a two-strain bacterial system that self-synthesizes and structures a synthetic extracellular matrix of proteins. We engineered Caulobacter crescentus to secrete an extracellular matrix protein composed of elastin-like polypeptide (ELP) hydrogel fused to Supercharged SpyCatcher (SC(-)). This biopolymer was secreted at levels of 60 mg/L, an unprecedented level of biopolymer secretion by a gram-negative bacterium. The ELP domain was swapped with either a crosslinkable variant of ELP or resilin-like polypeptide, demonstrating this system is flexible. The SC(-)-ELP matrix protein bound specifically and covalently to the cell surface of a C. crescentus strain that displays a high-density array of SpyTag peptides via its engineered Surface-layer. Our work develops protein design rules for Type I secretion in C. crescentus, and demonstrates the autonomous secretion and assembly of programmable extracellular protein matrices, offering a path forward towards the formation of cohesive engineered living materials. IMPORTANCEEngineered living materials (ELM) aim to mimic characteristics of natural occurring systems, bringing the benefits of self-healing, synthesis, autonomous assembly, and responsiveness to traditional materials. Previous research has shown the potential of replicating the bacterial extracellular matrix (ECM) to mimic biofilms. However, these efforts require energy intensive processing or have limited tunability. We propose a bacterially-synthesized system that manipulates the protein content of the ECM, allowing for programmable interactions and autonomous material formation. To achieve this, we engineered a two-strain system to secrete a synthetic extracellular protein matrix (sEPM). This work is a step towards understanding the necessary parameters to engineering living cells to autonomously construct ELMs.

synthetic biology↗

bioRxiv2020

A helical assembly of human ESCRT-I scaffolds reverse-topology membrane scission

The ESCRT complexes drive membrane scission in HIV-1 release, autophagosome closure, MVB biogenesis, cytokinesis, and other cell processes. ESCRT-I is the most upstream complex and bridges the system to HIV-1 Gag in virus release. The crystal structure of the headpiece of human ESCRT-I comprising TSG101:VPS28:VPS37B:MVB12A was determined, revealing an ESCRT-I helical assembly with a 12 molecule repeat. Electron microscopy confirmed that ESCRT-I subcomplexes form helical filaments in solution. Mutation of VPS28 helical interface residues blocks filament formation in vitro and autophagosome closure and HIV-1 release in human cells. Coarse grained simulations of ESCRT assembly at HIV-1 budding sites suggest that formation of a 12-membered ring of ESCRT-I molecules is a geometry-dependent checkpoint during late stages of Gag assembly and HIV-1 budding, and templates ESCRT-III assembly for membrane scission. These data show that ESCRT-I is not merely a bridging adaptor, but has an essential scaffolding and mechanical role in its own right.

biophysics↗