Acceleration of the sliding movement of actin filaments with the use of a non-motile mutant myosin in in vitro motility assays driven by skeletal muscle heavy meromyosin

Network analysis of differentially expressed genes involved in oral submucous fibrosis and oral squamous cell carcinoma: a comparative approach

OBJECTIVE

Oral submucous fibrosis (OSMF) is categorized as an oral potentially malignant disorder (OPMD) with an increased risk of occurrence of oral squamous cell carcinoma (OSCC). In this study, we aimed to identify the hub genes associated with OSMF and OSCC.

STUDY DESIGN

Using RStudio, a set of differentially expressed genes (DEGs) were identified in (A) OSMF, (B) OSCC, and (C) comparative OSMF-OSCC category, obtained from Gene Expression Omnibus (GEO). The Protein to Protein Interaction (PPI) Network, hub genes, and functional annotation were determined using Search Tool for the Retrieval of Interacting Genes (STRING), Cytoscape, and SR-Plot, Database for Annotation, Visualization and Integrated Discovery (DAVID).

RESULTS

A total of 2081, 2320, and 3295 DEGs were obtained from the OSMF, OSCC, and comparative categories, respectively. Hub gene and gene enrichment analysis revealed that the genes in (A) MYH6, TTN, TNNT3, MYL1, TPM2, ACTN3, NEB, MYL2, TNNT1, and TPM1; (B) CD4, SELL, CD28, CD27, PRF1, CD80, GZMB, CD40LG, ITGAX, and IL4; and (C) CD4, CD8A, CTLA4, CD28, GZMB, IL79, CD69, CD40LG, IFNG, and CD80 categories, were associated with muscle contraction, cell proliferation, and malignant transformation.

CONCLUSIONS

Hub genes and functional enrichment analysis revealed the diagnostic genes and the genes responsible for the malignant transformation in OSMF, OSCC, and the comparative category. A panel of identified genes will be of clinical significance in targeted therapy in future studies. (Oral Surg Oral Med Oral Pathol Oral Radiol YEAR;VOL:page range).

Multiple Mechanisms to Regulate Actin Functions: "Fundamental" Versus Lineage-Specific Mechanisms and Hierarchical Relationships

Eukaryotic actin filaments play a central role in numerous cellular functions, with each function relying on the interaction of actin filaments with specific actin-binding proteins. Understanding the mechanisms that regulate these interactions is key to uncovering how actin filaments perform diverse roles at different cellular locations. Several distinct classes of actin regulatory mechanisms have been proposed and experimentally supported. However, these mechanisms vary in their nature and hierarchy. For instance, some operate under the control of others, highlighting hierarchical relationships. Additionally, while certain mechanisms are fundamental and ubiquitous across eukaryotes, others are lineage-specific. Here, we emphasize the fundamental importance and functional significance of the following actin regulatory mechanisms: the biochemical regulation of actin nucleators, the ATP hydrolysis-dependent aging of actin filaments, thermal fluctuation- and mechanical strain-dependent conformational changes of actin filaments, and cooperative conformational changes induced by actin-binding proteins.

Exploitation of Engineered Light-Switchable Myosin XI for Nanotechnological Applications

For certain nanotechnological applications of the contractile proteins actin and myosin, e.g., in biosensing and network-based biocomputation, it would be desirable to temporarily switch on/off motile function in parts of nanostructured devices, e.g., for sorting or programming. Myosin XI motor constructs, engineered with a light-switchable domain for switching actin motility between high and low velocities (light-sensitive motors (LSMs) below), are promising in this regard. However, they were not designed for use in nanotechnology, where longevity of operation, long shelf life, and selectivity of function in specific regions of a nanofabricated network are important. Here, we tested if these criteria can be fulfilled using existing LSM constructs or if additional developments will be required. We demonstrated extended shelf life as well as longevity of the actin-propelling function compared to those in previous studies. We also evaluated several approaches for selective immobilization with a maintained actin propelling function in dedicated nanochannels only. Whereas selectivity was feasible using certain nanopatterning combinations, the reproducibility was not satisfactory. In summary, the study demonstrates the feasibility of using engineered light-controlled myosin XI motors for myosin-driven actin transport in nanotechnological applications. Before use for, e.g., sorting or programming, additional work is however needed to achieve reproducibility of the nanofabrication and, further, optimize the motor properties.

Buckling instabilities and spatio-temporal dynamics of active elastic filaments

Biological filaments driven by molecular motors tend to experience tangential propulsive forces also known as active follower forces. When such a filament encounters an obstacle, it deforms, which reorients its follower forces and alters its entire motion. If the filament pushes a cargo, the friction on the cargo can be enough to deform the filament, thus affecting the transport properties of the cargo. Motivated by cytoskeletal filament motility assays, we study the dynamic buckling instabilities of a two-dimensional slender elastic filament driven through a dissipative medium by tangential propulsive forces in the presence of obstacles or cargo. We observe two distinct instabilities. When the filament's head is pinned or experiences significant translational but little rotational drag from its cargo, it buckles into a steadily rotating coiled state. When it is clamped or experiences both significant translational and rotational drag from its cargo, it buckles into a periodically beating, overall translating state. Using minimal analytically tractable models, linear stability theory and fully nonlinear computations, we study the onset of each buckling instability, characterize each buckled state, and map out the phase diagram of the system. Finally, we use particle-based Brownian dynamics simulations to show our main results are robust to moderate noise and steric repulsion. Overall, our results provide a unified framework to understand the dynamics of tangentially propelled filaments and filament-cargo assemblies.