TUBright: A Peptide Probe for Imaging Microtubules

Liquid-liquid phase separation of microtubule-binding proteins in the regulation of spindle assembly

Cell division is a highly regulated process essential for the accurate segregation of chromosomes. Central to this process is the assembly of a bipolar mitotic spindle, a highly dynamic microtubule (MT)-based structure responsible for chromosome movement. The nucleation and dynamics of MTs are intricately regulated by MT-binding proteins. Over the recent years, various MT-binding proteins have been reported to undergo liquid-liquid phase separation, forming either single- or multi-component condensates on MTs. Herein, we provide a comprehensive summary of the phase separation characteristics of these proteins. We underscore their critical roles in MT nucleation, spindle assembly and kinetochore-MT attachment during the cell division process. Furthermore, we discuss the current challenges and various remaining unsolved problems, highlights the ongoing research efforts aimed at a deeper understanding of the role of the phase separation process during spindle assembly and orientation. Our review aims to contribute to the collective knowledge in this area and stimulate further investigations that will enhance our comprehension of the intricate mechanisms governing cell division.

CYLD/HDAC6 signaling regulates the interplay between epithelial-mesenchymal transition and ciliary homeostasis during pulmonary fibrosis

The primary cilium behaves as a platform for sensing and integrating extracellular cues to control a plethora of cellular activities. However, the functional interaction of this sensory organelle with epithelial-mesenchymal transition (EMT) during pulmonary fibrosis remains unclear. Here, we reveal a critical role for cylindromatosis (CYLD) in reciprocally linking the EMT program and ciliary homeostasis during pulmonary fibrosis. A close correlation between the EMT program and primary cilia is observed in bleomycin-induced pulmonary fibrosis as well as TGF-β-induced EMT model. Mechanistic study reveals that downregulation of CYLD underlies the crosstalk between EMT and ciliary homeostasis by inactivating histone deacetylase 6 (HDAC6) during pulmonary fibrosis. Moreover, manipulation of primary cilia is an effective means to modulate the EMT program. Collectively, these results identify a pivotal role for the CYLD/HDAC6 signaling in regulating the reciprocal interplay between the EMT program and ciliary homeostasis during pulmonary fibrosis.

Targeted degradation of membrane and extracellular proteins with LYTACs

Targeted protein degradation technology has gained substantial momentum over the past two decades as a revolutionary strategy for eliminating pathogenic proteins that are otherwise refractory to treatment. Among the various approaches developed to harness the body's innate protein homeostasis mechanisms for this purpose, lysosome targeting chimeras (LYTACs) that exploit the lysosomal degradation pathway by coupling the target proteins with lysosome-trafficking receptors represent the latest innovation. These chimeras are uniquely tailored to degrade proteins that are membrane-bound and extracellular, encompassing approximately 40% of all proteome. Several novel LYTAC formulas have been developed recently, providing valuable insights for the design and development of therapeutic degraders. This review delineates the recent progresses of LYTAC technology, its practical applications, and the factors that dictate target degradation efficiency. The potential and emerging trends of this technology are discussed as well. LYTAC technology offers a promising avenue for targeted protein degradation, potentially revolutionizing the therapeutic landscape for numerous diseases.

An engineered DNA aptamer-based PROTAC for precise therapy of p53-R175H hotspot mutant-driven cancer

Targeting oncogenic mutant p53 represents an attractive strategy for cancer treatment due to the high frequency of gain-of-function mutations and ectopic expression in various cancer types. Despite extensive efforts, the absence of a druggable active site for small molecules has rendered these mutants therapeutically non-actionable. Here we develop a selective and effective proteolysis-targeting chimera (PROTAC) for p53-R175H, a common hotspot mutant with dominant-negative and oncogenic activity. Using a novel iterative molecular docking-guided post-SELEX (systematic evolution of ligands by exponential enrichment) approach, we rationally engineer a high-performance DNA aptamer with improved affinity and specificity for p53-R175H. Leveraging this resulting aptamer as a binder for PROTACs, we successfully developed a selective p53-R175H degrader, named dp53m. dp53m induces the ubiquitin-proteasome-dependent degradation of p53-R175H while sparing wildtype p53. Importantly, dp53m demonstrates significant antitumor efficacy in p53-R175H-driven cancer cells both in vitro and in vivo, without toxicity. Moreover, dp53m significantly and synergistically improves the sensitivity of these cells to cisplatin, a commonly used chemotherapy drug. These findings provide evidence of the potential therapeutic value of dp53m in p53-R175H-driven cancers.

Multifaceted roles of PDCD6 both within and outside the cell

Programmed cell death protein 6 (PDCD6) is an evolutionarily conserved Ca2+-binding protein. PDCD6 is involved in regulating multifaceted and pleiotropic cellular processes in different cellular compartments. For instance, nuclear PDCD6 regulates apoptosis and alternative splicing. PDCD6 is required for coat protein complex II-dependent endoplasmic reticulum-to-Golgi apparatus vesicular transport in the cytoplasm. Recent advances suggest that cytoplasmic PDCD6 is involved in the regulation of cytoskeletal dynamics and innate immune responses. Additionally, membranous PDCD6 participates in membrane repair through endosomal sorting complex required for transport complex-dependent membrane budding. Interestingly, extracellular vesicles are rich in PDCD6. Moreover, abnormal expression of PDCD6 is closely associated with many diseases, especially cancer. PDCD6 is therefore a multifaceted but pivotal protein in vivo. To gain a more comprehensive understanding of PDCD6 functions and to focus and stimulate PDCD6 research, this review summarizes key developments in its role in different subcellular compartments, processes, and pathologies.

Dynein Light Intermediate Chains Exhibit Different Arginine Methylation Patterns

BACKGROUND

The motor protein dynein is integral to retrograde transport along microtubules and interacts with numerous cargoes through the recruitment of cargo-specific adaptor proteins. This interaction is mediated by dynein light intermediate chain subunits LIC1 (DYNC1LI1) and LIC2 (DYNC1LI2), which govern the adaptor binding and are present in distinct dynein complexes with overlapping and unique functions.

METHODS

Using bioinformatics, we analyzed the C-terminal domains (CTDs) of LIC1 and LIC2, revealing similar structural features but diverse post-translational modifications (PTMs). The methylation status of LIC2 and the proteins involved in this modification were examined through immunoprecipitation and immunoblotting analyses. The specific methylation sites on LIC2 were identified through a site-directed mutagenesis analysis, contributing to a deeper understanding of the regulatory mechanisms of the dynein complex.

RESULTS

We found that LIC2 is specifically methylated at the arginine 397 residue, a reaction that is catalyzed by protein arginine methyltransferase 1 (PRMT1).

CONCLUSIONS

The distinct PTMs of the LIC subunits offer a versatile mechanism for dynein to transport diverse cargoes efficiently. Understanding how these PTMs influence the functions of LIC2, and how they differ from LIC1, is crucial for elucidating the role of dynein-related transport pathways in a range of diseases. The discovery of the arginine 397 methylation site on LIC2 enhances our insight into the regulatory PTMs of dynein functions.

INPP5E Regulates the Distribution of Phospholipids on Cilia in RPE1 Cells

BACKGROUND

Primary cilia are static microtubule-based structures protruding from the cell surface and present on most vertebrate cells. The appropriate localization of phospholipids is essential for cilia formation and stability. INPP5E is a cilia-localized inositol 5-phosphatase; its deletion alters the phosphoinositide composition in the ciliary membrane, disrupting ciliary function.

METHODS

The EGFP-2xP4MSidM, PHPLCδ1-EGFP, and SMO-tRFP plasmids were constructed by the Gateway system to establish a stable RPE1 cell line. The INPP5E KO RPE1 cell line was constructed with the CRISPR/Cas9 system. The localization of INPP5E and the distribution of PI(4,5)P2 and PI4P were examined by immunofluorescence microscopy. The fluorescence intensity co-localized with cilia was quantified by ImageJ.

RESULTS

In RPE1 cells, PI4P is localized at the ciliary membrane, whereas PI(4,5)P2 is localized at the base of cilia. Knocking down or knocking out INPP5E alters this distribution, resulting in the distribution of PI(4,5)P2 along the ciliary membrane and the disappearance of PI4P from the cilia. Meanwhile, PI(4,5)P2 is located in the ciliary membrane labeled by SMO-tRFP.

CONCLUSIONS

INPP5E regulates the distribution of phosphoinositide on cilia. PI(4,5)P2 localizes at the ciliary membrane labeled with SMO-tRFP, indicating that ciliary pocket membrane contains PI(4,5)P2, and phosphoinositide composition in early membrane structures may differ from that in mature ciliary membrane.

CCL2-CCR2 signaling axis in obesity and metabolic diseases

Obesity and metabolic diseases, such as insulin resistance, type 2 diabetes, nonalcoholic fatty liver disease, and cardiovascular ailments, represent formidable global health challenges, bearing considerable implications for both morbidity and mortality rates. It has become increasingly evident that chronic, low-grade inflammation plays a pivotal role in the genesis and advancement of these conditions. The involvement of C-C chemokine ligand 2 (CCL2) and its corresponding receptor, C-C chemokine receptor 2 (CCR2), has been extensively documented in numerous inflammatory maladies. Recent evidence indicates that the CCL2/CCR2 pathway extends beyond immune cell recruitment and inflammation, exerting a notable influence on the genesis and progression of metabolic syndrome. The present review seeks to furnish a comprehensive exposition of the CCL2-CCR2 signaling axis within the context of obesity and metabolic disorders, elucidating its molecular mechanisms, functional roles, and therapeutic implications.

The interconnections between the microtubules and mitochondrial networks in cardiocerebrovascular diseases: Implications for therapy

Microtubules, a highly dynamic cytoskeleton, participate in many cellular activities including mechanical support, organelles interactions, and intracellular trafficking. Microtubule organization can be regulated by modification of tubulin subunits, microtubule-associated proteins (MAPs) or agents modulating microtubule assembly. Increasing studies demonstrate that microtubule disorganization correlates with various cardiocerebrovascular diseases including heart failure and ischemic stroke. Microtubules also mediate intracellular transport as well as intercellular transfer of mitochondria, a power house in cells which produce ATP for various physiological activities such as cardiac mechanical function. It is known to all that both microtubules and mitochondria participate in the progression of cancer and Parkinson's disease. However, the interconnections between the microtubules and mitochondrial networks in cardiocerebrovascular diseases remain unclear. In this paper, we will focus on the roles of microtubules in cardiocerebrovascular diseases, and discuss the interplay of mitochondria and microtubules in disease development and treatment. Elucidation of these issues might provide significant diagnostic value as well as potential targets for cardiocerebrovascular diseases.