Endosomal recycling controls plasma membrane area during mitosis

Renormalized mechanics and stochastic thermodynamics of growing model protocells

Uncovering the rules governing the nonequilibrium dynamics of the membranes that define biological cells is of central importance to understanding the physics of living systems. We theoretically and computationally investigate the behavior of model protocells-flexible quasispherical vesicles-that exchange membrane constituents, internal volume, and heat with an external reservoir. The excess chemical potential and osmotic pressure difference imposed by the reservoir act as generalized thermodynamic driving forces that modulate vesicle morphology. We identify an associated nonequilibrium morphological transition between a weakly driven regime, in which growing vesicles remain quasispherical, and a strongly driven regime, in which vesicles accommodate rapid membrane uptake by developing surface wrinkles. This transition emerges due to the renormalization of membrane mechanical properties by nonequilibrium driving. Further, using insights from stochastic thermodynamics we propose a minimal vesicle growth-shape law that remains robust even in strongly driven, far-from-equilibrium regimes.

The localization and function of the moonlighting protein Clathrin during oocyte maturation

Clathrin is one of the leading players in the endocytic process during oocyte maturation. Immunofluorescence and transmission electron analysis on fully-grown germinal vesicle (GV) mouse oocytes shows Clathrin localization on the cortical region with three peculiar patterns: complete, incomplete, and half-moon. The first configuration is characterized by Clathrin lattices along the cortex; the second is represented by Clathrin lattices interrupted by invaginations forming coated vesicles as an indication of active endocytosis. The half-moon profile, the less frequent but the most interesting one, refers to Clathrin lattices distributed to one-half of the cell. The in vivo analysis of organelles' positioning and cytoplasmic rearrangements, performed to understand the possible relation between endocytosis and oocyte maturation, suggests that the half-moon pattern indicates those fully-grown oocytes that may have likely undergone Germinal Vesicle Breakdown, MI, and MII. Our results show that, before oocytes undergo maturation, Clathrin localizes on the side of the cell, opposite to future spindle migration, thus marking spindle orientation in mouse oocytes.

From dusk till dawn: cell cycle progression in the red seaweed Gracilariopsis chorda (Rhodophyta)

The conserved eukaryotic functions of cell cycle genes have primarily been studied using animal/plant models and unicellular algae. Cell cycle progression and its regulatory components in red (Rhodophyta) seaweeds are poorly understood. We analyzed diurnal gene expression data to investigate the cell cycle in the red seaweed Gracilariopsis chorda. We identified cell cycle progression and transitions in G. chorda which are induced by interactions of key regulators such as E2F/DP, RBR, cyclin-dependent kinases, and cyclins from dusk to dawn. However, several typical CDK inhibitor proteins are absent in red seaweeds. Interestingly, the G1-S transition in G. chorda is controlled by delayed transcription of GINS subunit 3. We propose that the delayed S phase entry in this seaweed may have evolved to minimize DNA damage (e.g., due to UV radiation) during replication. Our results provide important insights into cell cycle-associated physiology and its molecular mechanisms in red seaweeds.

The Plasma Membrane and Mechanoregulation in Cells

Cells inhabit a mechanical microenvironment that they continuously sense and adapt to. The plasma membrane (PM), serving as the boundary of the cell, plays a pivotal role in this process of adaptation. In this Review, we begin by examining well-studied processes where mechanoregulation proves significant. Specifically, we highlight examples from the immune system and stem cells, besides discussing processes involving fibroblasts and other cell types. Subsequently, we discuss the common molecular players that facilitate the sensing of the mechanical signal and transform it into a chemical response covering integrins YAP/TAZ and Piezo. We then review how this understanding of molecular elements is leveraged in drug discovery and tissue engineering alongside a discussion of the methodologies used to measure mechanical properties. Focusing on the processes of endocytosis, we discuss how cells may respond to altered membrane mechanics using endo- and exocytosis. Through the process of depleting/adding the membrane area, these could also impact membrane mechanics. We compare pathways from studies illustrating the involvement of endocytosis in mechanoregulation, including clathrin-mediated endocytosis (CME) and the CLIC/GEEC (CG) pathway as central examples. Lastly, we review studies on cell-cell fusion during myogenesis, the mechanical integrity of muscle fibers, and the reported and anticipated roles of various molecular players and processes like endocytosis, thereby emphasizing the significance of mechanoregulation at the PM.

The AP-2 complex interacts with γ-TuRC and regulates the proliferative capacity of neural progenitors

Centrosomes are organelles that nucleate microtubules via the activity of gamma-tubulin ring complexes (γ-TuRC). In the developing brain, centrosome integrity is central to the progression of the neural progenitor cell cycle, and its loss leads to microcephaly. We show that NPCs maintain centrosome integrity via the endocytic adaptor protein complex-2 (AP-2). NPCs lacking AP-2 exhibit defects in centrosome formation and mitotic progression, accompanied by DNA damage and accumulation of p53. This function of AP-2 in regulating the proliferative capacity of NPCs is independent of its role in clathrin-mediated endocytosis and is coupled to its association with the GCP2, GCP3, and GCP4 components of γ-TuRC. We find that AP-2 maintains γ-TuRC organization and regulates centrosome function at the level of MT nucleation. Taken together, our data reveal a novel, noncanonical function of AP-2 in regulating the proliferative capacity of NPCs and open new avenues for the identification of novel therapeutic strategies for the treatment of neurodevelopmental and neurodegenerative disorders with AP-2 complex dysfunction.

A Rab39-Klp98A-Rab35 endocytic recycling pathway is essential for rapid Golgi-dependent furrow ingression

Ingression of the plasma membrane is an essential part of the cell topology-distorting repertoire and a key element in animal cell cytokinesis. Many embryos have rapid cleavage stages in which they are furrowing powerhouses, quickly forming and disassembling cleavage furrows on timescales of just minutes. Previous work has shown that cytoskeletal proteins and membrane trafficking coordinate to drive furrow ingression, but where these membrane stores are derived from and how they are directed to furrowing processes has been less clear. Here, we identify an extensive Rab35/Rab4>Rab39/Klp98A>trans-Golgi network (TGN) endocytic recycling pathway necessary for fast furrow ingression in the Drosophila embryo. Rab39 is present in vesiculotubular compartments at the TGN where it receives endocytically derived cargo through a Rab35/Rab4-dependent pathway. A Kinesin-3 family member, Klp98A, drives the movements and tubulation activities of Rab39, and disruption of this Rab39-Klp98A-Rab35 pathway causes deep furrow ingression defects and genomic instability. These data suggest that an endocytic recycling pathway rapidly remobilizes membrane cargo from the cell surface and directs it to the trans-Golgi network to permit the initiation of new cycles of cleavage furrow formation.

Lipid Polarization during Cytokinesis

The plasma membrane of eukaryotic cells is composed of a large number of lipid species that are laterally segregated into functional domains as well as asymmetrically distributed between the outer and inner leaflets. Additionally, the spatial distribution and organization of these lipids dramatically change in response to various cellular states, such as cell division, differentiation, and apoptosis. Division of one cell into two daughter cells is one of the most fundamental requirements for the sustenance of growth in all living organisms. The successful completion of cytokinesis, the final stage of cell division, is critically dependent on the spatial distribution and organization of specific lipids. In this review, we discuss the properties of various lipid species associated with cytokinesis and the mechanisms involved in their polarization, including forward trafficking, endocytic recycling, local synthesis, and cortical flow models. The differences in lipid species requirements and distribution in mitotic vs. male meiotic cells will be discussed. We will concentrate on sphingolipids and phosphatidylinositols because their transbilayer organization and movement may be linked via the cytoskeleton and thus critically regulate various steps of cytokinesis.

Insights on the Role of PGRMC1 in Mitotic and Meiotic Cell Division

During mitosis, chromosome missegregation and cytokinesis defects have been recognized as hallmarks of cancer cells. Cytoskeletal elements composing the spindle and the contractile ring and their associated proteins play crucial roles in the faithful progression of mitotic cell division. The hypothesis that PGRMC1, most likely as a part of a yet-to-be-defined complex, is involved in the regulation of spindle function and, more broadly, the cytoskeletal machinery driving cell division is particularly appealing. Nevertheless, more than ten years after the preliminary observation that PGRMC1 changes its localization dynamically during meiotic and mitotic cell division, this field of research has remained a niche and needs to be fully explored. To encourage research in this fascinating field, in this review, we will recap the current knowledge on PGRMC1 function during mitotic and meiotic cell division, critically highlighting the strengths and limitations of the experimental approaches used so far. We will focus on known interacting partners as well as new putative associated proteins that have recently arisen in the literature and that might support current as well as new hypotheses of a role for PGRMC1 in specific spindle subcompartments, such as the centrosome, kinetochores, and the midzone/midbody.

Lysosome exocytosis is required for mitosis in mammalian cells

Mitosis, the accurate segregation of duplicated genetic material into what will become two new daughter cells, is accompanied by extensive membrane remodelling and membrane trafficking activities. Early in mitosis, adherent cells partially detach from the substratum, round up and their surface area decreases. This likely results from an endocytic uptake of plasma membrane material. As cells enter cytokinesis they re-adhere, flatten and exhibit an associated increase in surface area. The identity of the membrane donor for this phase of mitosis remains unclear. In this paper we demonstrate how lysosomes dynamically redistribute during mitosis and exocytose. Antagonism of lysosomal exocytosis by pharmacological and genetic approaches causes mitosis failure in a significant proportion of cells. We speculate that either lysosomal membrane or luminal content release, possibly both, are therefore required for normal mitosis progression. These findings are important as they reveal a new process required for successful cell division.

Membrane area gain and loss during cytokinesis

In cytokinesis of animal cells, the cell is symmetrically divided into two. Since the cell's volume is conserved, the projected area has to increase to allow for the change of shape. Here we aim to predict how membrane gain and loss adapt during cytokinesis. We work with a kinetic model in which membrane turnover depends on membrane tension and cell shape. We apply this model to a series of calculated vesicle shapes as a proxy for the shape of dividing cells. We find that the ratio of kinetic turnover parameters changes nonmonotonically with cell shape, determined by the dependence of exocytosis and endocytosis on membrane curvature. Our results imply that controlling membrane turnover will be crucial for the successful division of artificial cells.

GRP75-driven, cell-cycle-dependent macropinocytosis of Tat/pDNA-Ca2+ nanoparticles underlies distinct gene therapy effect in ovarian cancer

Practice of tumor-targeted suicide gene therapy is hampered by unsafe and low efficient delivery of plasmid DNA (pDNA). Using HIV-Tat-derived peptide (Tat) to non-covalently form Tat/pDNA complexes advances the delivery performance. However, this innovative approach is still limited by intracellular delivery efficiency and cell-cycle status. In this study, Tat/pDNA complexes were further condensed into smaller, nontoxic nanoparticles by Ca²⁺ addition. Formulated Tat/pDNA-Ca²⁺ nanoparticles mainly use macropinocytosis for intercellular delivery, and their macropinocytic uptake was persisted in mitosis (M-) phase and highly activated in DNA synthesis (S-) phase of cell-cycle. Over-expression or phosphorylation of a mitochondrial chaperone, 75-kDa glucose-regulated protein (GRP75), promoted monopolar spindle kinase 1 (MPS1)-controlled centrosome duplication and cell-cycle progress, but also driven cell-cycle-dependent macropinocytosis of Tat/pDNA-Ca²⁺ nanoparticles. Further in vivo molecular imaging based on DF (Fluc-eGFP)-TF (RFP-Rluc-HSV-ttk) system showed that Tat/pDNA-Ca²⁺ nanoparticles exhibited highly suicide gene therapy efficiency in mouse model xenografted with human ovarian cancer. Furthermore, arresting cell-cycle at S-phase markedly enhanced delivery performance of Tat/pDNA-Ca²⁺ nanoparticles, whereas targeting GRP75 reduced their macropinocytic delivery. More importantly, in vivo targeting GRP75 combined with cell-cycle or macropinocytosis inhibitors exhibited distinct suicide gene therapy efficiency. In summary, our data highlight that mitochondrial chaperone GRP75 moonlights as a biphasic driver underlying cell-cycle-dependent macropinocytosis of Tat/pDNA-Ca²⁺ nanoparticles in ovarian cancer.

Fine-tuning cell organelle dynamics during mitosis by small GTPases

During mitosis, the allocation of genetic material concurs with organelle transformation and distribution. The coordination of genetic material inheritance with organelle dynamics directs accurate mitotic progression, cell fate determination, and organismal homeostasis. Small GTPases belonging to the Ras superfamily regulate various cell organelles during division. Being the key regulators of membrane dynamics, the dysregulation of small GTPases is widely associated with cell organelle disruption in neoplastic and non-neoplastic diseases, such as cancer and Alzheimer's disease. Recent discoveries shed light on the molecular properties of small GTPases as sophisticated modulators of a remarkably complex and perfect adaptors for rapid structure reformation. This review collects current knowledge on small GTPases in the regulation of cell organelles during mitosis and highlights the mediator role of small GTPase in transducing cell cycle signaling to organelle dynamics during mitosis.

The small GTPase RAB10 regulates endosomal recycling of the LDL receptor and transferrin receptor in hepatocytes

The low-density lipoprotein receptor (LDLR) mediates the hepatic uptake of circulating low-density lipoproteins (LDLs), a process that modulates the development of atherosclerotic cardiovascular disease. We recently identified RAB10, encoding a small GTPase, as a positive regulator of LDL uptake in hepatocellular carcinoma cells (HuH7) in a genome-wide CRISPR screen, though the underlying molecular mechanism for this effect was unknown. We now report that RAB10 regulates hepatocyte LDL uptake by promoting the recycling of endocytosed LDLR from RAB11-positive endosomes to the plasma membrane. We also show that RAB10 similarly promotes the recycling of the transferrin receptor, which binds the transferrin protein that mediates the transport of iron in the blood, albeit from a distinct RAB4-positive compartment. Taken together, our findings suggest a model in which RAB10 regulates LDL and transferrin uptake by promoting both slow and rapid recycling routes for their respective receptor proteins.

Emerging roles of mitotic autophagy

Lysosomes exert pleiotropic functions to maintain cellular homeostasis and degrade autophagy cargo. Despite the great advances that have boosted our understanding of autophagy and lysosomes in both physiology and pathology, their function in mitosis is still controversial. During mitosis, most organelles are reshaped or repurposed to allow the correct distribution of chromosomes. Mitotic entry is accompanied by a reduction in sites of autophagy initiation, supporting the idea of an inhibition of autophagy to protect the genetic material against harmful degradation. However, there is accumulating evidence revealing the requirement of selective autophagy and functional lysosomes for a faithful chromosome segregation. Degradation is the most-studied lysosomal activity, but recently described alternative functions that operate in mitosis highlight the lysosomes as guardians of mitotic progression. Because the involvement of autophagy in mitosis remains controversial, it is important to consider the specific contribution of signalling cascades, the functions of autophagic proteins and the multiple roles of lysosomes, as three entangled, but independent, factors controlling genomic stability. In this Review, we discuss the latest advances in this area and highlight the therapeutic potential of targeting autophagy for drug development.

Amoeboid-like migration ensures correct horizontal cell layer formation in the developing vertebrate retina

Migration of cells in the developing brain is integral for the establishment of neural circuits and function of the central nervous system. While migration modes during which neurons employ predetermined directional guidance of either preexisting neuronal processes or underlying cells have been well explored, less is known about how cells featuring multipolar morphology migrate in the dense environment of the developing brain. To address this, we here investigated multipolar migration of horizontal cells in the zebrafish retina. We found that these cells feature several hallmarks of amoeboid-like migration that enable them to tailor their movements to the spatial constraints of the crowded retina. These hallmarks include cell and nuclear shape changes, as well as persistent rearward polarization of stable F-actin. Interference with the organization of the developing retina by changing nuclear properties or overall tissue architecture hampers efficient horizontal cell migration and layer formation showing that cell-tissue interplay is crucial for this process. In view of the high proportion of multipolar migration phenomena observed in brain development, the here uncovered amoeboid-like migration mode might be conserved in other areas of the developing nervous system.

Single-cell monitoring of dry mass and dry mass density reveals exocytosis of cellular dry contents in mitosis

Cell mass and composition change with cell cycle progression. Our previous work characterized buoyant mass dynamics in mitosis (Miettinen et al., 2019), but how dry mass and cell composition change in mitosis has remained unclear. To better understand mitotic cell growth and compositional changes, we develop a single-cell approach for monitoring dry mass and the density of that dry mass every ~75 s with 1.3% and 0.3% measurement precision, respectively. We find that suspension grown mammalian cells lose dry mass and increase dry mass density following mitotic entry. These changes display large, non-genetic cell-to-cell variability, and the changes are reversed at metaphase-anaphase transition, after which dry mass continues accumulating. The change in dry mass density causes buoyant and dry mass to differ specifically in early mitosis, thus reconciling existing literature on mitotic cell growth. Mechanistically, cells in early mitosis increase lysosomal exocytosis, and inhibition of lysosomal exocytosis decreases the dry mass loss and dry mass density increase in mitosis. Overall, our work provides a new approach for monitoring single-cell dry mass and dry mass density, and reveals that mitosis is coupled to extensive exocytosis-mediated secretion of cellular contents.

Lysosomal Changes in Mitosis

The recent discovery demonstrating that the leakage of cathepsin B from mitotic lysosomes assists mitotic chromosome segregation indicates that lysosomal membrane integrity can be spatiotemporally regulated. Unlike many other organelles, structural and functional alterations of lysosomes during mitosis remain, however, largely uncharted. Here, we demonstrate substantial differences in lysosomal proteome, lipidome, size, and pH between lysosomes that were isolated from human U2OS osteosarcoma cells either in mitosis or in interphase. The combination of pharmacological synchronization and mitotic shake-off yielded ~68% of cells in mitosis allowing us to investigate mitosis-specific lysosomal changes by comparing cell populations that were highly enriched in mitotic cells to those mainly in the G1 or G2 phases of the cell cycle. Mitotic cells had significantly reduced levels of lysosomal-associated membrane protein (LAMP) 1 and the active forms of lysosomal cathepsin B protease. Similar trends were observed in levels of acid sphingomyelinase and most other lysosomal proteins that were studied. The altered protein content was accompanied by increases in the size and pH of LAMP2-positive vesicles. Moreover, mass spectrometry-based shotgun lipidomics of purified lysosomes revealed elevated levels of sphingolipids, especially sphingomyelin and hexocylceramide, and lysoglyserophospholipids in mitotic lysosomes. Interestingly, LAMPs and acid sphingomyelinase have been reported to stabilize lysosomal membranes, whereas sphingomyelin and lysoglyserophospholipids have an opposite effect. Thus, the observed lysosomal changes during the cell cycle may partially explain the reduced lysosomal membrane integrity in mitotic cells.

The mechanosensitive Piezo1 channel controls endosome trafficking for an efficient cytokinetic abscission

Mechanical forces are exerted throughout cytokinesis, the final step of cell division. Yet, how forces are transduced and affect the signaling dynamics of cytokinetic proteins remains poorly characterized. We now show that the mechanosensitive Piezo1 channel is activated at the intercellular bridge (ICB) connecting daughter cells to regulate abscission. Inhibition of Piezo1 caused multinucleation both in vitro and in vivo. Piezo1 positioning at the ICB during cytokinesis depends on Pacsin3. Pharmacological and genetic inhibition of Piezo1 or Pacsin3 resulted in mislocation of Rab11-family-interacting protein 3 (Rab11-FIP3) endosomes, apoptosis-linked gene 2-interacting protein X (ALIX), and endosomal sorting complex required for transport III (ESCRT-III). Furthermore, we identified FIP3 as the link between Piezo1-generated Ca²⁺ signals and ALIX delivery to the ICB, where ALIX recruits the ESCRT-III component charged multivesicular body protein 4B, which promotes abscission. These results provide a different view of how mechanical forces participate in cytokinesis and identify Piezo1 as a key modulator of endosome trafficking.

Sources of variability in nanoparticle uptake by cells

Understanding how nano-sized objects are taken up by cells is important for applications within medicine (nanomedicine), as well as to avoid unforeseen hazard due to nanotechnology (nanosafety). Even within the same cell population, one typically observes a large cell-to-cell variability in nanoparticle uptake, raising the question of the underlying cause(s). Here we investigate cell-to-cell variability in polystyrene nanoparticle uptake by HeLa cells, with generalisations of the results to silica nanoparticles and liposomes, as well as to A549 and primary human umbilical vein endothelial cells. We show that uptake of nanoparticles is correlated with cell size within a cell population, thereby reproducing and generalising previous reports highlighting the role of cell size in nanoparticle uptake. By repeatedly isolating (using fluorescence-activated cell sorting) the cells that take up the most and least nanoparticles, respectively, and performing RNA sequencing on these cells separately, we examine the underlying gene expression that contributes to high and low polystyrene nanoparticle accumulation in HeLa cells. We can thereby show that cell size is not the sole driver of cell-to-cell variability, but that other cellular characteristics also play a role. In contrast to cell size, these characteristics are more specific to the object (nanoparticle or protein) being taken up, but are nevertheless highly heterogeneous, complicating their detailed identification. Overall, our results highlight the complexity underlying the cellular features that determine nanoparticle uptake propensity.

Effects of the Laplace pressure on the cells during cytokinesis

The Laplace pressure is one of the most fundamental regulators that determine cell shape and function, and thus has been receiving widespread attention. Here, we systemically investigate the effect of the Laplace pressure on the shape and function of the cells during cytokinesis. We find that the Laplace pressure during cytokinesis can directly control the distribution and size of cell blebbing and adjust the symmetry of cell division by virtue of changing the characteristics of cell blebbing. Further, we demonstrate that the Laplace pressure changes the structural uniformity of cell boundary to regulate the symmetry of cell division. Our findings provide further insights as to the important role of the Laplace pressure in regulating the symmetry of cell division during cytokinesis.

All-purpose nanostrategy based on dose deposition enhancement, cell cycle arrest, DNA damage, and ROS production as prostate cancer radiosensitizer for potential clinical translation

Radiotherapy (RT) is one of the main treatments for men with prostate cancer (PCa). To date, numerous sophisticated nano-formulations as radiosensitizers have been synthesized with inspiring therapeutic effects both in vitro and in vivo; however, almost all the attention has been paid on the enhanced dose deposition effect by secondary electrons of nanomaterials with high atomic numbers (Z); despite this, cell-cycle arrest, DNA damage, and also reactive oxygen species (ROS) production are critical working mechanisms that account for radiosensitization. Herein, an 'all-purpose' nanostrategy based on dose deposition enhancement, cell cycle arrest, and ROS production as prostate cancer radiosensitizer for potential clinical translation was proposed. The rather simple structure of docetaxel-loaded Au nanoparticles (NPs) with prostate specific membrane antigen (PSMA) ligand conjugation have been successfully synthesized. Enhanced cellular uptake achieved via the selective internalization of the NPs by PCa cells with positive PSMA expression could guarantee enhanced dose deposition. Moreover, the as-synthesized nanosystem could effectively arrest the cell cycle at G2/M phases, which would reduce the ability of DNA damage repair for more irradiation sensitive of the PCa cells. Moreover, the G2/M phase arrest would further promote cascade retention and the enrichment of NPs within the cells. Furthermore, ROS generation and double strand breaks greatly promoted by NPs under irradiation (IR) could also provide an underlying basis for effective radiosensitizers. In vitro and in vivo investigations confirmed the as-synthesized NPs as an effective nano-radiosensitizer with ideal safety. More importantly, all moieties within the present nanosystem have been approved by FDA for the purpose of PCa treatment, thus making it highly attractive for clinical translation.

Endocytosis in the context-dependent regulation of individual and collective cell properties

Endocytosis allows cells to transport particles and molecules across the plasma membrane. In addition, it is involved in the termination of signalling through receptor downmodulation and degradation. This traditional outlook has been substantially modified in recent years by discoveries that endocytosis and subsequent trafficking routes have a profound impact on the positive regulation and propagation of signals, being key for the spatiotemporal regulation of signal transmission in cells. Accordingly, endocytosis and membrane trafficking regulate virtually every aspect of cell physiology and are frequently subverted in pathological conditions. Two key aspects of endocytic control over signalling are coming into focus: context-dependency and long-range effects. First, endocytic-regulated outputs are not stereotyped but heavily dependent on the cell-specific regulation of endocytic networks. Second, endocytic regulation has an impact not only on individual cells but also on the behaviour of cellular collectives. Herein, we will discuss recent advancements in these areas, highlighting how endocytic trafficking impacts complex cell properties, including cell polarity and collective cell migration, and the relevance of these mechanisms to disease, in particular cancer.

Visualizing bleb mass dynamics in single cells using quantitative phase microscopy

Understanding biological responses to directed energy (DE) is critical to ensure the safety of personnel within the Department of Defense. At the Air Force Research Laboratory, we have developed or adapted advanced optical imaging systems that quantify biophysical responses to DE. One notable cellular response to DE exposure is the formation of blebs, or semi-spherical protrusions of the plasma membrane in living cells. In this work, we demonstrate the capacity of quantitative phase imaging (QPI) to both visualize and quantify the formation of membrane blebs following DE exposure. QPI is an interferometric imaging tool that uses optical path length as a label-free contrast mechanism and is sensitive to the non-aqueous mass density, or dry mass, of living cells. Blebs from both CHO-K1 and U937 cells were generated after exposure to a series of 600 ns, 21.2 kV/cm electric pulses. These blebs were visualized in real time, and their dry mass relative to the rest of the cell body was quantified as a function of time. It is our hope that this system will lead to an improved understanding of both DE-induced and apoptotic blebbing.

Dynamic interplay between cell membrane tension and clathrin-mediated endocytosis

Deformability of the plasma membrane, the outermost surface of metazoan cells, allows cells to be dynamic, mobile and flexible. Factors that affect this deformability, such as tension on the membrane, can regulate a myriad of cellular functions, including membrane resealing, cell motility, polarisation, shape maintenance, membrane area control and endocytic vesicle trafficking. This review focuses on mechanoregulation of clathrin-mediated endocytosis (CME). We first delineate the origins of cell membrane tension and the factors that yield to its spatial and temporal fluctuations within cells. We then review the recent literature demonstrating that tension on the membrane is a fast-acting and reversible regulator of CME. Finally, we discuss tension-based regulation of endocytic clathrin coat formation during physiological processes.

A Focus on "Bio" in Bio-Nanoscience: The Impact of Biological Factors on Nanomaterial Interactions

Bio-nanoscience research encompasses studies on the interactions of nanomaterials with biological structures or what is commonly referred to as the biointerface. Fundamental studies on the influence of nanomaterial properties, including size, shape, composition, and charge, on the interaction with the biointerface have been central in bio-nanoscience to assess nanomaterial efficacy and safety for a range of biomedical applications. However, the state of the cells, tissues, or biological models can also influence the behavior of nanomaterials at the biointerface and their intracellular processing. Focusing on the "bio" in bio-nano, this review discusses the impact of biological properties at the cellular, tissue, and whole organism level that influences nanomaterial behavior, including cell type, cell cycle, tumor physiology, and disease states. Understanding how the biological factors can be addressed or exploited to enhance nanomaterial accumulation and uptake can guide the design of better and suitable models to improve the outcomes of materials in nanomedicine.

Cell Cycle Control of Nanoplastics Internalization in Phytoplankton

Nanoparticles (NPs) for delivering chemotherapeutic drugs are now in clinical trials, and cellular uptake of NPs plays an important role in determining the drug delivery efficiency. Herein, we reported that the bioaccumulation and internalization of NPs were governed by the cell cycle. Specifically, we found that the bioaccumulation of NPs was more favored in the G₂/M stages, followed by the S and G₀/G₁ stages. We demonstrated that three key parameters-clathrin-mediated endocytosis capacity, algal cell membrane permeability, and exopolymer substance (EPS) thickness-were critical in the bioaccumulation of NPs during the cell cycling process. Over the 24-h average duration of cell cycle, clathrin-mediated endocytosis capacity was much higher at the S stage than that at the G₀/G₁ and G₂/M stages. Besides, cell membrane permeability was measured to be higher in S and G₂/M stages while the lowest in G₀/G₁ stage. We have also identified the change of EPS thickness during the 24-h cell cycle. Transition from G₀/G₁ to S and G₂/M induced the attenuation in EPS thickness, and the thinnest EPS was found at the end of mitosis. The cell cycle control NPs internalization were further verified by exposing Ag nanoparticles to algae at different cell cycle stages, confirming the important roles of EPS thickness and cell cycle control in the dynamic internalization processes. The present study highlights the important roles of cell cycle controlling the NPs bioaccumulation and internalization, with possible implications in maximizing NPs internalization efficiency while reducing the cost.

Inherited nuclear pore substructures template post-mitotic pore assembly

Nuclear envelope assembly during late mitosis includes rapid formation of several thousand complete nuclear pore complexes (NPCs). This efficient use of NPC components (nucleoporins or "NUPs") is essential for ensuring immediate nucleocytoplasmic communication in each daughter cell. We show that octameric subassemblies of outer and inner nuclear pore rings remain intact in the mitotic endoplasmic reticulum (ER) after NPC disassembly during prophase. These "inherited" subassemblies then incorporate into NPCs during post-mitotic pore formation. We further show that the stable subassemblies persist through multiple rounds of cell division and the accompanying rounds of NPC mitotic disassembly and post-mitotic assembly. De novo formation of NPCs from newly synthesized NUPs during interphase will then have a distinct initiation mechanism. We postulate that a yet-to-be-identified modification marks and "immortalizes" one or more components of the specific octameric outer and inner ring subcomplexes that then template post-mitotic NPC assembly during subsequent cell cycles.

Brain-specific functions of the endocytic machinery

Endocytosis is an essential cellular process required for multiple physiological functions, including communication with the extracellular environment, nutrient uptake, and signaling by the cell surface receptors. In a broad sense, endocytosis is accomplished through either constitutive or ligand-induced invagination of the plasma membrane, which results in the formation of the plasma membrane-retrieved endocytic vesicles, which can either be sent for degradation to the lysosomes or recycled back to the PM. This additional function of endocytosis in membrane retrieval has been adopted by excitable cells, such as neurons, for membrane equilibrium maintenance at synapses. The last two decades were especially productive with respect to the identification of brain-specific functions of the endocytic machinery, which additionally include but not limited to regulation of neuronal differentiation and migration, maintenance of neuron morphology and synaptic plasticity, and prevention of neurotoxic aggregates spreading. In this review, we highlight the current knowledge of brain-specific functions of endocytic machinery with a specific focus on three brain cell types, neuronal progenitor cells, neurons, and glial cells.

Imaging mitotic processes in three dimensions with lattice light-sheet microscopy

There are few technologies that can capture mitotic processes occurring in three-dimensional space with the desired spatiotemporal resolution. Due to such technical limitations, our understanding of mitosis, which has been studied since the early 1880s, is still incomplete with regard to mitotic processes and their regulatory mechanisms at a molecular level. A recently developed high-resolution type of light-sheet microscopy, lattice light-sheet microscopy (LLSM), has achieved unprecedented spatiotemporal resolution scans of intracellular spaces at the whole-cell level. This technology enables experiments that were not possible before (e.g., tracking of growth of every spindle microtubule end and discrimination of individual chromosomes in living cells), thus providing a new avenue for the analysis of mitotic processes. Herein, principles of LLSM technology are introduced, as well as experimental techniques that became possible with LLSM. In addition, issues remaining to be solved for use of this technology in mitosis research, big image data problems, are presented to help guide mitosis research into a new era.

Lysosomal degradation ensures accurate chromosomal segregation to prevent chromosomal instability

Lysosomes, as primary degradative organelles, are the endpoint of different converging pathways, including macroautophagy. To date, lysosome degradative function has been mainly studied in interphase cells, while their role during mitosis remains controversial. Mitosis dictates the faithful transmission of genetic material among generations, and perturbations of mitotic division lead to chromosomal instability, a hallmark of cancer. Heretofore, correct mitotic progression relies on the orchestrated degradation of mitotic factors, which was mainly attributed to ubiquitin-triggered proteasome-dependent degradation. Here, we show that mitotic transition also relies on lysosome-dependent degradation, as impairment of lysosomes increases mitotic timing and leads to mitotic errors, thus promoting chromosomal instability. Furthermore, we identified several putative lysosomal targets in mitotic cells. Among them, WAPL, a cohesin regulatory protein, emerged as a novel SQSTM1-interacting protein for targeted lysosomal degradation. Finally, we characterized an atypical nuclear phenotype, the toroidal nucleus, as a novel biomarker for genotoxic screenings. Our results establish lysosome-dependent degradation as an essential event to prevent chromosomal instability.Abbreviations: 3D: three-dimensional; APC/C: anaphase-promoting complex; ARL8B: ADP ribosylation factor like GTPase 8B; ATG: autophagy-related; BORC: BLOC-one-related complex; CDK: cyclin-dependent kinase; CENPE: centromere protein E; CIN: chromosomal instability; ConcA: concanamycin A; CQ: chloroquine; DAPI: 4,6-diamidino-2-penylinole; FTI: farnesyltransferase inhibitors; GFP: green fluorescent protein; H2B: histone 2B; KIF: kinesin family member; LAMP2: lysosomal associated membrane protein 2; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MEF: mouse embryonic fibroblast; MTOR: mechanistic target of rapamycin kinase; PDS5B: PDS5 cohesin associated factor B; SAC: spindle assembly checkpoint; PLEKHM2: pleckstrin homology and RUN domain containing M2; SQSTM1: sequestosome 1; TEM: transmission electron microscopy; ULK1: unc-51 like autophagy activating kinase 1; UPS: ubiquitin-proteasome system; v-ATPase: vacuolar-type H+-translocating ATPase; WAPL: WAPL cohesion release factor.

Subcellular localization of glypican-5 is associated with dynamic motility of the human mesenchymal stem cell line U3DT

Glypican-5 (GPC5) is a heparan sulfate proteoglycan (HSPG) localized to the plasma membrane. We previously reported that in the human mesenchymal stem cell line UE6E7T-3, GPC5 is overexpressed in association with transformation and promotes cell proliferation by acting as a co-receptor for Sonic hedgehog signaling. In this study, we found using immunofluorescence microscopy that in transformed cells (U3DT), GPC5 localized not only at primary cilia on the cell surface, but also at the leading edge of migrating cells, at the intercellular bridge and blebs during cytokinesis, and in extracellular vesicles. In each subcellular region, GPC5 colocalized with fibroblast growth factor receptor (FGFR) and the small GTPases Rab11 and ARF6, indicating that GPC5 is delivered to these regions by Rab11-associated recycling endosomes. These colocalizations suggest that GPC5 plays an important role in FGF2 stimulation of cell migration, which was abrogated by knockdown of GPC5. Our findings indicate that GPC5 plays a role in regulation of U3DT cell migration and provides several insights into the functions of GPC5 that could be elucidated by future studies.

Cyclin-dependent Kinase 1 and Aurora Kinase choreograph mitotic storage and redistribution of a growth factor receptor

Endosomal trafficking of receptors and associated proteins plays a critical role in signal processing. Until recently, it was thought that trafficking was shut down during cell division. Thus, remarkably, the regulation of trafficking during division remains poorly characterized. Here we delineate the role of mitotic kinases in receptor trafficking during asymmetric division. Targeted perturbations reveal that Cyclin-dependent Kinase 1 (CDK1) and Aurora Kinase promote storage of Fibroblast Growth Factor Receptors (FGFRs) by suppressing endosomal degradation and recycling pathways. As cells progress through metaphase, loss of CDK1 activity permits differential degradation and targeted recycling of stored receptors, leading to asymmetric induction. Mitotic receptor storage, as delineated in this study, may facilitate rapid reestablishment of signaling competence in nascent daughter cells. However, mutations that limit or enhance the release of stored signaling components could alter daughter cell fate or behavior thereby promoting oncogenesis.

This study provides fundamental insights into the crosstalk between cell division and signaling, with implications for cancer. High-resolution in vivo analysis reveals that dividing cells sequester signal receptor proteins into internal compartments; stored receptors are then redistributed as cells complete division.

Functional reciprocity of proteins involved in mitosis and endocytosis

Mitosis and endocytosis are two fundamental cellular processes essential for maintaining a eukaryotic life. Mitosis partitions duplicated chromatin enveloped in the nuclear membrane into two new cells, whereas endocytosis takes in extracellular substances through membrane invagination. These two processes are spatiotemporally separated and seemingly unrelated. However, recent studies have uncovered that endocytic proteins have moonlighting functions in mitosis, and mitotic complexes manifest additional roles in endocytosis. In this review, we summarize important proteins or protein complexes that participate in both processes, compare their mechanism of action, and discuss the rationale behind this multifunctionality. We also speculate on the possible origin of the functional reciprocity from an evolutionary perspective.

Cell density-dependent accumulation of low polarity gold nanocluster in cultured vascular endothelial cells

We have previously reported the cytotoxicity and various biological responses of organic-inorganic hybrid molecules. However, because all the molecules used were electrophilic, the effect of the hybrid molecule without electrophilicity remains unclear. The glutathione-protected gold nanocluster, Au₂₅(SG)₁₈, is an organic-inorganic hybrid molecule that shows a low intramolecular polarity and high stability. In this study, we examined the cytotoxicity and intracellular accumulation of Au₂₅(SG)₁₈ in cultured vascular endothelial cells and compared these characteristics with those of negatively charged gold nanoparticles (AuNPs). Both Au₂₅(SG)₁₈ and AuNPs accumulated in vascular endothelial cells in a dose-dependent manner without cytotoxicity and more accumulation was observed at low cell densities. However, Au₂₅(SG)₁₈ accumulated significantly less than AuNPs in the cells. These results suggest that the intramolecular polarity of organic-inorganic hybrid molecules could regulate intracellular accumulation.

The multifaceted role of cell cycle regulators in the coordination of growth and metabolism

Adapting to changes in nutrient availability and environmental conditions is a fundamental property of cells. This adaptation requires a multi‐directional coordination between metabolism, growth, and the cell cycle regulators (consisting of the family of cyclin‐dependent kinases (CDKs), their regulatory subunits known as cyclins, CDK inhibitors, the retinoblastoma family members, and the E2F transcription factors). Deciphering the mechanisms accountable for this coordination is crucial for understanding various patho‐physiological processes. While it is well established that metabolism and growth affect cell division, this review will focus on recent observations that demonstrate how cell cycle regulators coordinate metabolism, cell cycle progression, and growth. We will discuss how the cell cycle regulators directly regulate metabolic enzymes and pathways and summarize their involvement in the endolysosomal pathway and in the functions and dynamics of mitochondria.

Kinase activity-independent role of EphA2 in the regulation of M-phase progression

Cell division is a tightly regulated, essential process for cell proliferation. Very recently, we reported that EphA2 is phosphorylated at Ser897, via the Cdk1/MEK/ERK/RSK pathway, during M phase and contributes to proper M-phase progression by maintaining cortical rigidity via the EphA2pSer897/ephexin4/RhoG pathway. Here, we show that EphA2 kinase activity is dispensable for M-phase progression. Although EphA2 knockdown delayed this progression, the delay was rescued by an EphA2 mutant expression with an Asp739 to Asn substitution, as well as by wild-type EphA2. Western blotting analysis confirmed that the Asp739Asn mutant lost its EphA2 kinase activity. Like wild-type EphA2, the Asp739Asn mutant was localized to the plasma membrane irrespective of cell cycle. While RhoG localization to the plasma membrane was decreased in EphA2 knockdown cells, it was rescued by re-expression of wild-type EphA2 but not via the mutant containing the Ser897 to Ala substitution. This confirmed our recent report that phosphorylation at Ser897 is responsible for RhoG localization to the plasma membrane. In agreement with the M-phase progression's rescue effect, the Asp739Asn mutant rescued RhoG localization in EphA2 knockdown cells. These results suggest that EphA2 regulates M-phase progression in a manner independent of its kinase activity.

Focal adhesion kinase is activated by microtubule-depolymerizing agents and regulates membrane blebbing in human endothelial cells

Microtubule-depolymerizing agents can selectively disrupt tumor vessels via inducing endothelial membrane blebbing. However, the mechanism regulating blebbing is largely unknown. IMB5046 is a newly discovered microtubule-depolymerizing agent. Here, the functions of focal adhesion kinase (FAK) during IMB5046-induced blebbing and the relevant mechanism are studied. We found that IMB5046 induced membrane blebbing and reassembly of focal adhesions in human vascular endothelial cells. Both FAK inhibitor and knock-down expression of FAK inhibited IMB5046-induced blebbing. Mechanism study revealed that IMB5046 induced the activation of FAK via GEF-H1/ Rho/ ROCK/ MLC2 pathway. cRGD peptide, a ligand of integrin, also blocked IMB5046-induced blebbing. After activation, FAK further promoted the phosphorylation of MLC2. This positive feedback loop caused more intensive actomyosin contraction and continuous membrane blebbing. FAK inhibitor blocked membrane blebbing via inhibiting actomyosin contraction, and stimulated stress fibre formation via promoting the phosphorylation of HSP27. Conclusively, these results demonstrate that FAK is a molecular switch controlling endothelial blebbing and stress fibre formation. Our study provides a new molecular mechanism for microtubule-depolymerizing agents to be used as vascular disrupting agents.

Toxicity of binary mixtures of Al2O3 and ZnO nanoparticles toward fibroblast and bronchial epithelium cells

The objective of this study was to examine the cytotoxic effects of binary mixtures of Al₂O₃ and ZnO NPs using mouse fibroblast cells (L929) and human bronchial epithelial cells (BEAS-2B) as biological test systems. The synergistic, additive, or antagonistic behavior of the binary mixture was also investigated. In toxicity experiments, cellular morphology, mitochondrial function (MTT assay), apoptosis, nuclear size and shape, clonogenic assays, and damage based upon oxidative stress parameters were assessed under control and NPs exposure conditions. Although Abbott modeling results provided no clear evidence of the binary mixture of Al₂O₃ and ZnO NPs exhibiting synergistic toxicity, some specific assays such as apoptosis, nuclear size and shape, clonogenic assay, activities of antioxidant enzymatic enzymes catalase, superoxide dismutase, and levels of glutathione resulted in enhanced toxicity for the mixtures with 1 and 1.75 toxic units (TU) toward both cell types. Data demonstrated that co-presence of Al₂O₃ and ZnO NPs in the same environment might lead to more realistic environmental conditions. Our findings indicate cytotoxicity of binary mixtures of Al₂O₃ and ZnO NPs produced greater effects compared to toxicity of either individual compound.

SRRF-Stream Imaging of Optogenetically Controlled Furrow Formation Shows Localized and Coordinated Endocytosis and Exocytosis Mediating Membrane Remodeling

Cleavage furrow formation during cytokinesis involves extensive membrane remodeling. In the absence of methods to exert dynamic control over these processes, it has been a challenge to examine the basis of this remodeling. Here we used a subcellular optogenetic approach to induce this at will and found that furrow formation is mediated by actomyosin contractility, retrograde plasma membrane flow, localized decrease in membrane tension, and endocytosis. FRAP, 4-D imaging, and inhibition or upregulation of endocytosis or exocytosis show that ARF6 and Exo70 dependent localized exocytosis supports a potential model for intercellular bridge elongation. TIRF and Super Resolution Radial Fluctuation (SRRF) stream microscopy show localized VAMP2-mediated exocytosis and incorporation of membrane lipids from vesicles into the plasma membrane at the front edge of the nascent daughter cell. Thus, spatially separated but coordinated plasma membrane depletion and addition are likely contributors to membrane remodeling during cytokinetic processes.

Regulation of the Total Cell Surface Area in Dividing Dictyostelium Cells

When a cell divides into two daughter cells, the total cell surface area should increase. There are two models for membrane supply to support cell division: (1) unfolding of small surface membrane reservoirs such as microvilli or wrinkles and (2) exocytosis of intracellular vesicles. Here, we precisely measured the total cell surface area in dividing Dictyostelium cells, flattened by the agar overlay that eliminated the complexity of unfolding surface membrane reservoirs. Because the cells divided normally under the agar overlay, unfolding of surface membrane reservoirs was not required for cell division. Under the agar overlay, the total cell surface area slightly decreased from the interphase to the metaphase and then increased about 20% during cytokinesis. Both endocytosis and exocytosis were suppressed in the early mitotic phase but recovered during cytokinesis. The imbalance of endocytosis and exocytosis could contribute to the changes observed in the cell surface area. Clathrin-dependent endocytosis was also substantially suppressed during cytokinesis, but contrary to previous reports in cultured animal cells, it did not significantly contribute to the regulation of the cell surface area. Furrowing during cytokinesis was indispensable for the cell membrane increase, and vice versa.

The crosstalk between microtubules, actin and membranes shapes cell division

Mitotic progression is orchestrated by morphological and mechanical changes promoted by the coordinated activities of the microtubule (MT) cytoskeleton, the actin cytoskeleton and the plasma membrane (PM). MTs assemble the mitotic spindle, which assists sister chromatid separation, and contact the rigid and tensile actomyosin cortex rounded-up underneath the PM. Here, we highlight the dynamic crosstalk between MTs, actin and cell membranes during mitosis, and discuss the molecular connections between them. We also summarize recent views on how MT traction forces, the actomyosin cortex and membrane trafficking contribute to spindle positioning in isolated cells in culture and in epithelial sheets. Finally, we describe the emerging role of membrane trafficking in synchronizing actomyosin tension and cell shape changes with cell-substrate adhesion, cell-cell contacts and extracellular signalling events regulating proliferation.

Limitation in Controlling the Morphology of Mammalian Vero Cells Induced by Cell Division on Asymmetric Tungsten-Silicon Oxide Nanocomposite

Engineered nanomaterials are often used in tissue engineering applications to influence and manipulate the behavior of cells. Recently, a number of tungsten-silicon oxide nanocomposite devices containing equal width (symmetric) tungsten and silicon oxide parallel line comb structures were developed and used by our group. The devices induced over 90% of seeded cells (Vero) to align within ±20° of the axes of 10 µm wide tungsten lines. Furthermore, a mathematical model was successfully developed to predict this alignment behavior and forecast the minimum width of isolated tungsten lines required to induce such behavior. However, the mechanism by which the widths of the symmetrical tungsten and silicon oxide lines induce the alignment behavior is still unknown. Furthermore, the model was never tested on more complex asymmetrical structures. Herewith, experiments were conducted with mammalian cells on complex asymmetrical structures with unequal tungsten and silicon oxide line widths. Results showed that the model could be extended to more complex pattern structures. In addition, cell morphology on the patterned structures reset during cell division because of mitotic rounding, which reduced the population of cells that elongated and aligned on the tungsten lines. Ultimately, we concluded that it was impossible to achieve a 100% alignment with cells having unsynchronized cell cycles because cell rounding during mitosis took precedence over cell alignment; in other words, internal chemical cues had a stronger role in cell morphology than external cues.

Mechanical conditions for stable symmetric cell constriction

Cell constriction is a decisive step for division in many cells. However, its physical pathway remains poorly understood, calling for a quantitative analysis of the forces required in different cytokinetic scenarios. Using a model cell composed by a flexible membrane (actin cortex and cell membrane) that encloses the cytoplasm, we study the mechanical conditions necessary for stable symmetric constriction under radial equatorial forces using analytical and numerical methods. We deduce that stable symmetric constriction requires positive effective spontaneous curvature, while spontaneous constriction requires a spontaneous curvature higher than the characteristic inverse cell size. Surface tension reduction (for example by actin cortex growth and membrane trafficking) increases the stability and spontaneity of cellular constriction. A reduction of external pressure also increases stability and spontaneity. Cells with prolate lobes (elongated cells) require lower stabilization forces than oblate-shaped cells (discocytes). We also show that the stability and spontaneity of symmetric constriction increase as constriction progresses. Our quantitative results settle the physical requirements for stable cytokinesis, defining a quantitative framework to analyze the mechanical role of the different constriction machinery and cytokinetic pathways found in real cells, so contributing to a deeper quantitative understanding of the physical mechanism of the cell division process.

Quantitative Analysis of Proteome in Non-functional Pituitary Adenomas: Clinical Relevance and Potential Benefits for the Patients

Background: Non-functional pituitary adenoma (NFPA) is a common tumor that occurs in the pituitary gland, and generally without any symptoms at its early stage and without clinical elevation of hormones, which is commonly diagnosed when it grows up to compress its surrounding tissues and organs. Currently, the pathogenesis of NFPA has not been clarified yet. It is necessary to investigate molecular alterations in NFPA, and identify reliable biomarkers and drug therapeutic targets for effective treatments. Methods: Tandem mass tags (TMT)-based quantitative proteomics was used to identify and quantify proteins in NFPAs. GO and KEGG enrichment analyses were used to analyze the identified proteins. Differentially expressed genes (DEGs) between NFPA and control tissues were obtained from GEO datasets. These two sets of protein and gene data were analyzed to obtain overlapped molecules (genes; proteins), followed by further GO and KEGG pathway analyses of these overlapped molecules, and molecular network analysis to obtain the hub molecules with Cytoscape. Two hub molecules (SRC and AKT1) were verified with Western blotting. Results: Totally 6076 proteins in NFPA tissues were identified, and 3598 DEGs between NFPA and control tissues were identified from GEO database. Overlapping analysis of 6076 proteins and 3598 DEGs obtained 1088 overlapped molecules (DEGs; proteins). KEGG pathway analysis of 6076 proteins obtained 114 statistically significant pathways, including endocytosis, and spliceosome signaling pathways. KEGG pathway analysis of 1088 overlapped molecules obtained 52 statistically significant pathways, including focal adhesion, cGMP-PKG pathway, and platelet activation signaling pathways. These pathways play important roles in cell energy supply, adhesion, and maintenance of the tumor microenvironment. According to the association degree in Cytoscape, ten hub molecules (DEGs; proteins) were identified, including GAPDH, ALB, ACACA, SRC, ENO2, CALM1, POTEE, HSPA8, DECR1, and AKT1. Western-blotting analysis confirmed the upregulated expressions of SRC and PTMScan experiment confirmed the increased levels of pAKT1, in NFPAs compared to controls. Conclusions: This study established the large-scale quantitative protein profiling of NFPA tissue proteome. It offers a basis for subsequent in-depth proteomics analysis of NFPAs, and insight into the molecular mechanism of NFPAs. It also provided the basic data to discover reliable biomarkers and therapeutic targets for NFPA patients.

Unusual proteins in Giardia duodenalis and their role in survival

The capacity of the parasite Giardia duodenalis to perform complex functions with minimal amounts of proteins and organelles has attracted increasing numbers of scientists worldwide, trying to explain how this parasite adapts to internal and external changes to survive. One explanation could be that G. duodenalis evolved from a structurally complex ancestor by reductive evolution, resulting in adaptation to its parasitic lifestyle. Reductive evolution involves the loss of genes, organelles, and functions that commonly occur in many parasites, by which the host renders some structures and functions redundant. However, there is increasing data that Giardia possesses proteins able to perform more than one function. During recent decades, the concept of moonlighting was described for multitasking proteins, which involves only proteins with an extra independent function(s). In this chapter, we provide an overview of unusual proteins in Giardia that present multifunctional properties depending on the location and/or parasite requirement. We also discuss experimental evidence that may allow some giardial proteins to be classified as moonlighting proteins by examining the properties of moonlighting proteins in general. Up to date, Giardia does not seem to require the numerous redundant proteins present in other organisms to accomplish its normal functions, and thus this parasite may be an appropriate model for understanding different aspects of moonlighting proteins, which may be helpful in the design of drug targets.

De novo lipogenesis at the mitotic exit is used for nuclear envelope reassembly/expansion. Implications for combined chemotherapy

Mitosis has been traditionally considered a metabolically inactive phase. We have previously shown, however, that extensive alterations in lipids occur as the cells traverse mitosis, including increased de novo fatty acid (FA) and phosphatidylcholine (PtdCho) synthesis and decreased lysophospholipid content. Given the diverse structural and functional properties of these lipids, we sought to study their metabolic fate and their importance for cell cycle completion. Here we show that FA and PtdCho synthesized at the mitotic exit are destined to the nuclear envelope. Importantly, FA and PtdCho synthesis, but not the decrease in lysophospholipid content, are necessary for cell cycle completion beyond G₂/M. Moreover, the presence of alternative pathways for PtdCho synthesis renders the cells less sensitive to its inhibition than to the impairment of FA synthesis. FA synthesis, thus, represents a cell cycle-related metabolic vulnerability that could be exploited for combined chemotherapy. We explored the combination of fatty acid synthase (FASN) inhibition with agents that act at different phases of the cell cycle. Our results show that the effect of FASN inhibition may be enhanced under some drug combinations.

Cyclin-dependent kinase-mediated phosphorylation of the exocyst subunit Exo84 in late G1 phase suppresses exocytic secretion and cell growth in yeast

In eukaryotic cells, the growth rate is strictly regulated for proper progression of the cell cycle. In the budding yeast Saccharomyces cerevisiae, it was previously shown that cell growth dramatically slows down when the cells start budding at the G₁/S transition. However, the molecular mechanism for this G₁/S-associated growth arrest is unclear. In this study, using exocytic secretion, cyclin-dependent kinase (CDK) assay, immunoprecipitation, and microscopy, we demonstrate that the exocyst subunit Exo84, which is known to be phosphorylated in mitosis, can also be phosphorylated directly by Cdk1 in the late G₁ phase. Of note, we found that the Cdk1-mediated Exo84 phosphorylation impairs exocytic secretion in the late G₁ phase. Using conditional cdc mutants and phosphodeficient and phosphomimetic exo84 mutants, we further observed that Cdk1-phosphoryated Exo84 inhibits the exocyst complex assembly, exocytic secretion, and cell growth, which may be important for proper execution of the G₁/S-phase transition before commitment to a complete cell cycle. Our results suggest that the direct Cdk1-mediated regulation of the exocyst complex critically contributes to the coordination of cell growth and cell cycle progression.

Age at mating and male quality influence female patterns of reproductive investment and survival

The trade-off between the allocation of resources toward somatic maintenance or reproduction is one of the fundamentals of life history theory and predicts that females invest in offspring at the expense of their longevity or vice versa. Mate quality may also affect life history trade-offs through mechanisms of sexual conflict; however, few studies have examined the interaction between mate quality and age at first mating in reproductive decisions. Using house crickets (Acheta domesticus), this study examines how survival and reproductive trade-offs change based on females' age at first reproduction and exposure to males of varying size. Females were exposed to either a large (presumably high-quality) or small male at an early (young), middle (intermediate), or advanced (old) age, and longevity and reproductive investment were subsequently tracked. Females mated at a young age had the largest number of eggs but the shortest total lifespans while females mated at older ages produced fewer eggs but had longer total lifespans. The trade-off between age at first mating and eggs laid appears to be mediated through higher egg-laying rates and shorter postmating lifespans in females mated later in life. Exposure to small males resulted in shorter lifespans and higher egg-laying rates for all females indicating that male manipulation of females, presumably through spermatophore contents, varies with male size in this species. Together, these data strongly support a trade-off between age at first reproduction and lifespan and support the role of sexual conflict in shaping patterns of reproduction.