Biology subjects

Liu, A. P.

Publications and source records attributed to Liu, A. P..

4 recordsLinked to original sources

bioRxiv2026

The filopodial scaffold polyphosphate dictates cell adhesion-versus-invasion decisions

Inorganic polyphosphate (polyP) is an ancient polymer conserved across all life, serving cell type and location specific functions in every major compartment. Yet its role at the plasma membrane, where it accumulates to peak levels in many primary cells, is largely unknown. Here we identify polyP as a stabilizing component of filopodia, actin based membrane protrusions that govern cell adhesion, contact inhibition, and chemotaxis. Elevating cellular polyP increases filopodial stability and enhances cell adhesion, whereas reducing polyP accelerates filopodial disassembly and promotes cell migration. Mechanistically, we find that polyP acts as a structural filopodial scaffold, recruiting and organizing IRSp53, a membrane curvature inducing protein. We show that metastatic fibroblasts and breast cancer organoids carry markedly reduced and intracellularly reorganized polyP levels relative to their non transformed counterparts. Restoring endogenous polyP via lipid nanoparticle delivery suppresses their invasive phenotypes and reverses prometastatic gene expression signatures, implicating polyP as a primordial tumor suppressor.

cell biology↗

bioRxiv2018

A synthetic biology platform for the reconstitution and mechanistic dissection of LINC complex assembly

The linker of nucleoskeleton and cytoskeleton (LINC) is a conserved nuclear envelope-spanning molecular bridge that is responsible for the mechanical integration of the nucleus with the cytoskeleton. LINC complexes are formed by a transluminal interaction between the outer and inner nuclear membrane KASH and SUN proteins, respectively. Despite recent structural insights, our mechanistic understanding of LINC complex assembly remains limited by the lack of an experimental system for its in vitro reconstitution and manipulation. Here, we describe artificial nuclear membranes (ANMs) as a synthetic biology platform based on mammalian cell-free expression for the rapid reconstitution of SUN proteins in supported lipid bilayers. We demonstrate that SUN1 and SUN2 are oriented in ANMs with solvent-exposed C-terminal KASH-binding SUN domains. We also find that SUN2 possesses a single transmembrane domain, while SUN1 possesses three. Finally, SUN protein-containing ANMs bind synthetic KASH peptides, thereby reconstituting the LINC complex core. This work represents the first in vitro reconstitution of KASH-binding SUN proteins in supported lipid bilayers using cell-free expression, which will be invaluable for testing proposed models of LINC complex assembly and its regulation.

synthetic biology↗

bioRxiv2017

A robust and tunable mitotic oscillator in artificial cells

Single-cell analysis is pivotal to deciphering complex phenomena like cellular heterogeneity, bistable switch, and oscillations, where a population ensemble cannot represent the individual behaviors. Bulk cell-free systems, despite having unique advantages of manipulation and characterization of biochemical networks, lack the essential single-cell information to understand a class of out-of-steady-state dynamics including cell cycles. Here we develop a novel artificial single-cell system by encapsulating Xenopus egg extracts in water-in-oil microemulsions to study mitotic dynamics. These \"cells\", adjustable in sizes and periods, sustain oscillations for over 30 cycles, and function in forms from the simplest cytoplasmic-only to the more complicated ones involving nuclei dynamics, mimicking real mitotic cells. Such innate flexibility and robustness make it key to studying clock properties of tunability and stochasticity. Our result also highlights energy supply as an important regulator of cell cycles. We demonstrate a simple, powerful, and likely generalizable strategy of integrating strengths of single-cell approaches into conventional in vitro systems to study complex clock functions.

systems biology↗

bioRxiv2017

Loss Of PTEN Promotes Formation Of Signaling-Specific Clathrin-Coated Pits

Defective endocytosis and vesicular trafficking of signaling receptors has recently emerged as a multifaceted hallmark of malignant cells. Clathrin-coated pits (CCPs), the fundamental unit of clathrin-mediated endocytosis, display highly heterogeneous dynamics on the plasma membrane where they can take from 20 seconds to over a minute to form cytosolic coated-vesicles. Despite the large number of cargo molecules that traffic through CCPs, it is not well understood whether signaling receptors activated in cancer, such as epidermal growth factor receptor (EGFR), are regulated through a specific subset of CCPs. The signaling lipid phosphatidylinositol (3,4,5)-triphosphate (PI(3,4,5)P3), which is dephosphorylated by phosphatase tensin homolog (PTEN), is a potent tumorigenic signaling lipid that is present in excess in many types of cancers. Using total internal reflection fluorescence microscopy and automated tracking and detection of CCPs, we find PTEN and EGF bound EGFR are enriched in a distinct subset of short-lived CCPs that corresponded with clathrin-dependent EGF-induced signaling. By deleting PTEN using CRISPR-Cas9 and reconstituting PTEN, we demonstrate that PTEN plays a role in the regulation of CCP dynamics; this appears to recapitulate CCP dynamics in highly metastatic PTEN-deleted cancer cells where we find a larger proportion of short-lived CCPs and higher initiation density compared to the normal cells. Furthermore, increased PI(3,4,5)P3 results in higher proportion of short-lived CCPs, an effect that recapitulates PTEN deletion. Our findings provide strong evidence for the existence of short-lived signaling-capable CCPs. Altogether, these findings demonstrate the importance of PTEN and PI(3,4,5)P3 in regulating CCP dynamics and assign a new function to PTEN as a modulator of signaling-capable CCPs.

cell biology↗