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Liquid-Liquid Phase Separation of the Focal Adhesion Protein p130Cas Regulates mRNA Translation


Core Concepts
Focal adhesion protein p130Cas drives the formation of liquid-liquid phase separated condensates in the cytoplasm, which contain mRNAs and RNA-binding proteins and regulate global protein translation in a cell adhesion-dependent manner.
Abstract
The study examines the behavior of the focal adhesion protein p130Cas and its ability to undergo liquid-liquid phase separation (LLPS) in cells. Key findings: p130Cas, which contains intrinsically disordered regions, forms dynamic cytoplasmic condensates that bud off from focal adhesions. These condensates exhibit typical LLPS characteristics like fusion, fission, and rapid exchange of components. The p130Cas condensates contain other focal adhesion proteins like paxillin and FAK, as well as mRNAs and RNA-binding proteins involved in mRNA translation regulation. Induction of large focal adhesions by plating cells on high concentrations of fibronectin leads to increased p130Cas condensate formation and suppression of global protein translation. This effect is dependent on p130Cas. Optogenetic induction of p130Cas condensates using a light-sensitive Cry2 system also reduces translation, directly linking p130Cas LLPS to translational regulation. Analysis of the mRNA content in the p130Cas condensates reveals enrichment of transcripts involved in cell cycle, survival, and cell-cell communication, many of which are also differentially regulated upon p130Cas overexpression. These results identify a novel mechanism by which integrin-mediated adhesion can regulate mRNA translation through the formation of p130Cas-driven liquid-liquid phase separated condensates in the cytoplasm.
Stats
Cells on high fibronectin show a ~35% decrease in global protein translation compared to cells on low fibronectin. Knockdown of p130Cas abolishes the inhibition of translation on high fibronectin and instead leads to an increase in translation. Optogenetic induction of p130Cas condensates causes a ~35% decrease in translation, which reverses when the condensates disassemble.
Quotes
"Liquid-liquid phase separation (LLPS) has emerged as a major organizing principle in cells." "Integrin-mediated adhesions share multiple features with LLPS. They can assemble, grow, split, fuse and disassemble in live cells, which often correlate with cell functions such as migration and gene expression." "Focal adhesion protein p130Cas drives formation of structures with the characteristics of LLPS that bud from focal adhesions into the cytoplasm."

Deeper Inquiries

How do the specific mRNA and protein components within the p130Cas condensates contribute to the regulation of translation and other cellular functions?

The mRNA and protein components within the p130Cas condensates play a crucial role in the regulation of translation and other cellular functions. These components are enriched in a subset of focal adhesion proteins, RNA binding proteins, and mRNAs that are implicated in inhibiting mRNA translation. The presence of RNA binding proteins like Ago2 and GW182 within the condensates suggests a role in miRNA-dependent mRNA regulation. Additionally, the mRNAs isolated from p130Cas condensates are associated with biological processes related to cell cycle progression, survival, and cell-cell communication. This indicates that the condensates may play a role in coordinating these cellular functions by regulating the translation of specific mRNAs. The dynamic behavior of these condensates, including fusion, fission, and rapid exchange of components, further supports their involvement in regulating gene expression and cellular activities.

What are the potential physiological or pathological implications of dysregulated p130Cas LLPS and its impact on translation in diseases like cancer or fibrosis?

Dysregulated p130Cas LLPS and its impact on translation can have significant physiological and pathological implications, especially in diseases like cancer or fibrosis. In cancer, aberrant translation regulation can lead to uncontrolled cell growth, proliferation, and metastasis. Dysregulated p130Cas LLPS may contribute to this by altering the translation of specific mRNAs involved in cell cycle progression, survival, and other oncogenic processes. In fibrosis, abnormal translation control can result in excessive extracellular matrix deposition and tissue scarring. Dysregulated p130Cas LLPS may play a role in this process by influencing the translation of mRNAs involved in fibrotic pathways. Understanding the role of p130Cas LLPS in these diseases could provide insights into potential therapeutic targets for cancer and fibrosis treatment.

Could the principles of p130Cas LLPS-mediated translational control be extended to other cellular phase-separated organelles and their role in gene expression regulation?

The principles of p130Cas LLPS-mediated translational control could potentially be extended to other cellular phase-separated organelles and their role in gene expression regulation. LLPS is a fundamental organizing principle in cells, regulating a wide array of cellular functions including gene expression. The dynamic behavior of phase-separated organelles, such as rapid exchange of components and fusion/splitting, is a common feature that allows for the organization and regulation of biochemical reactions. By studying the components and behavior of other phase-separated organelles, similar to p130Cas condensates, we can gain insights into how they contribute to gene expression regulation and cellular functions. Understanding the principles of LLPS-mediated translational control in different cellular contexts can provide a comprehensive view of how phase separation influences gene expression and cellular processes.
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