The cellular functions of clathrin

Protein kinase-D1 and downstream signaling mechanisms involved in GLUT4 translocation in cardiac muscle

The Ser/Thr kinase protein kinase-D1 (PKD1) is involved in induction of various cell physiological processes in the heart such as myocellular hypertrophy and inflammation, which may turn maladaptive during long-term stimulation. Of special interest is a key role of PKD1 in the regulation of cardiac substrate metabolism. Glucose and fatty acids are the most important substrates for cardiac energy provision, and the ratio at which they are utilized determines the health status of the heart. Cardiac glucose uptake is mainly regulated by translocation of the glucose transporter GLUT4 from intracellular stores (endosomes) to the sarcolemma, and fatty acid uptake via a parallel translocation of fatty acid transporter CD36 from endosomes to the sarcolemma. PKD1 is involved in the regulation of GLUT4 translocation, but not CD36 translocation, giving it the ability to modulate glucose uptake without affecting fatty acid uptake, thereby altering the cardiac substrate balance. PKD1 would therefore serve as an attractive target to combat cardiac metabolic diseases with a tilted substrate balance, such as diabetic cardiomyopathy. However, PKD1 activation also elicits cardiac hypertrophy and inflammation. Therefore, identification of the events upstream and downstream of PKD1 may provide superior therapeutic targets to alter the cardiac substrate balance. Recent studies have identified the lipid kinase phosphatidylinositol 4-kinase IIIβ (PI4KIIIβ) as signaling hub downstream of PKD1 to selectively stimulate GLUT4-mediated myocardial glucose uptake without inducing hypertrophy. Taken together, the PKD1 signaling pathway serves a pivotal role in cardiac glucose metabolism and is a promising target to selectively modulate glucose uptake in cardiac disease.

An overview of the safety and efficacy of LX-9211 in treating neuropathic pain conditions

INTRODUCTION

LX-9211 is a drug designed to treat neuropathic pain conditions. It functions by inhibiting the adaptor-associated kinase 1 (AAK1) enzyme which promotes clathrin-dependent endocytosis. Preclinical studies have shown that LX-9211 does produce a reduction in nociceptive related behaviors and produces no major adverse effects in rats. Thus, LX-9211 has advanced to clinical trials to assess its safety and efficacy in humans. So far, phase 1 and phase 2 clinical trials involving patients with postherpetic neuralgia and diabetic peripheral neuropathic pain have been conducted with phase 3 trials planned in the future.

AREAS COVERED

This paper highlights preclinical studies involving LX-9211 in rodents. Additionally, phase 1 clinical trials examining the safety of LX-9211 in healthy subjects as well as phase 2 studies looking at the safety and efficacy of LX-9211 compared to placebo in patients with diabetic peripheral neuropathic pain and postherpetic neuralgia are also discussed.

EXPERT OPINION

In phase 1 and phase 2 clinical trials conducted so far, LX-9211 has been shown to produce few adverse effects as well as cause a significantly greater reduction in pain compared to placebo. However, more clinical studies are needed to further assess its effects in humans to ensure its safety.

Primary Human Breast Cancer-Associated Endothelial Cells Favor Interactions with Nanomedicines

Cancer nanomedicines predominately rely on transport processes controlled by tumor-associated endothelial cells to deliver therapeutic and diagnostic payloads into solid tumors. While the dominant role of this class of endothelial cells for nanoparticle transport and tumor delivery is established in animal models, the translational potential in human cells needs exploration. Using primary human breast cancer as a model, the differential interactions of normal and tumor-associated endothelial cells with clinically relevant nanomedicine formulations are explored and quantified. Primary human breast cancer-associated endothelial cells exhibit up to ≈2 times higher nanoparticle uptake than normal human mammary microvascular endothelial cells. Super-resolution imaging studies reveal a significantly higher intracellular vesicle number for tumor-associated endothelial cells, indicating a substantial increase in cellular transport activities. RNA sequencing and gene expression analysis indicate the upregulation of transport-related genes, especially motor protein genes, in tumor-associated endothelial cells. Collectively, the results demonstrate that primary human breast cancer-associated endothelial cells exhibit enhanced interactions with nanomedicines, suggesting a potentially significant role for these cells in nanoparticle tumor delivery in human patients. Engineering nanoparticles that leverage the translational potential of tumor-associated endothelial cell-mediated transport into human solid tumors may lead to the development of safer and more effective clinical cancer nanomedicines.

Antimicrobial peptide A9K as a gene delivery vector in cancer cells

Designed peptides are promising biomaterials for biomedical applications. The amphiphilic cationic antimicrobial peptide (AMP), A9K, can self-assemble into nano-rod structures and has shown cancer cell selectivity and could therefore be a promising candidate for therapeutic delivery into cancer cells. In this paper, we investigate the selectivity of A9K for cancer cell models, examining its effect on two human cancer cell lines, A431 and HCT-116. Little or no activity was observed on the control, human dermal fibroblasts (HDFs). In the cancer cell lines the peptide inhibited cellular growth through changes in mitochondrial morphology and membrane potential while remaining harmless towards HDFs. In addition, the peptide can bind to and protect nucleic acids while transporting them into both 2D cultures and 3D spheroids of cancer cells. A9K showed high efficiency in delivering siRNA molecules into the centre of the spheroids. A9K was also explored in vivo, using a zebrafish (Danio rerio) development toxicity assay, showing that the peptide is safe at low doses. Finally, a high-content imaging screen, using RNA interference (RNAi) targeted towards cellular uptake, in HCT-116 cells was carried out. Our findings suggest that active cellular uptake is involved in peptide internalisation, mediated through clathrin-mediated endocytosis. These new discoveries make A9K attractive for future developments in clinical and biotechnological applications.

Biomarkers of chemotherapy-induced cardiotoxicity: toward precision prevention using extracellular vesicles

Detrimental side effects of drugs like doxorubicin, which can cause cardiotoxicity, pose barriers for preventing cancer progression, or treating cancer early through molecular interception. Extracellular vesicles (EVs) are valued for their potential as biomarkers of human health, chemical and molecular carcinogenesis, and therapeutics to treat disease at the cellular level. EVs are released both during normal growth and in response to toxicity and cellular death, playing key roles in cellular communication. Consequently, EVs may hold promise as precision biomarkers and therapeutics to prevent or offset damaging off-target effects of chemotherapeutics. EVs have promise as biomarkers of impending cardiotoxicity induced by chemotherapies and as cardioprotective therapeutic agents. However, EVs can also mediate cardiotoxic cues, depending on the identity and past events of their parent cells. Understanding how EVs mediate signaling is critical toward implementing EVs as therapeutic agents to mitigate cardiotoxic effects of chemotherapies. For example, it remains unclear how mixtures of EV populations from cells exposed to toxins or undergoing different stages of cell death contribute to signaling across cardiac tissues. Here, we present our perspective on the outlook of EVs as future clinical tools to mitigate chemotherapy-induced cardiotoxicity, both as biomarkers of impending cardiotoxicity and as cardioprotective agents. Also, we discuss how heterogeneous mixtures of EVs and transient exposures to toxicants may add complexity to predicting outcomes of exogenously applied EVs. Elucidating how EV cargo and signaling properties change during dynamic cellular events may aid precision prevention of cardiotoxicity in anticancer treatments and development of safer chemotherapeutics.

Recent Advances in Delivery of Peptide and Protein Therapeutics to the Brain

The classes of neuropharmaceuticals known as proteins and peptides serve as diagnostic tools and are involved in specific communication in the peripheral and central nervous systems. However, due to tight junctions resembling epithelial cells found in the blood-brain barrier (BBB) in vivo, they are typically excluded from transport from the blood to the brain. The drugs having molecular weight of less than 400 Dalton are able to cross the BBB via lipid-mediated free diffusion. However, large molecule therapeutics are devoid of these characteristics. As an alternative, these substances may be carried via chimeric peptide drug delivery systems, and assist in transcytosis through BBB with the aid of linker strategies. With their recent developments, several forms of nanoparticles, including poly (ethylene glycol)-poly(ε-caprolactone) copolymers, nanogels, liposomes, nanostructured lipid carriers, poly (D, L-lactide-co-glycolide) nanoparticles, chitosan, and solid lipid nanoparticles, have also been considered for their therapeutic applications. Moreover, the necessity for physiologic optimization of current drug delivery methods and their carriers to deliver therapeutic doses of medication into the brain for the treatment of various neurologic illnesses has also been emphasized. Therapeutic use of proteins and peptides has no neuroprotective impact in the absence of all these methods. Each tactic, however, has unique drawbacks and considerations. In this review, we discuss different drug delivery methods for therapeutic distribution of pharmaceuticals, primarily neuroproteins and neuropeptides, through endothelial capillaries via blood-brain barrier. Finally, we have also discussed the challenges and future perspective of protein and peptide therapeutics delivery to the brain. SIGNIFICANCE STATEMENT: Very few reports on the delivery of therapeutic protein and peptide nanoformulations are available in the literature. Herein, we attempted to discuss these nanoformulations of protein and peptide therapeutics used to treat brain diseases.

Effects of receptor properties on particle internalization through receptor-mediated endocytosis

Receptor-mediated endocytosis (RME) is a highly complex process carried out by bioparticles, such as viruses and drug carriers, to enter cells. The discovery of both clathrin-dependent and clathrin-free pathways makes the RME process even more intriguing. Numerical models have been developed to facilitate the exploration of the process. However, the impacts of the receptor properties on RME have been less studied partially due to the oversimplifications of the receptor models. In this paper, we implement a stochastic model to systematically investigate the effects of mechanical (receptor flexure), geometrical (receptor length) and biochemical (ligand-receptor cutoff) properties of receptors, on RME with and without the existence of clathrin. Our simulation results show that the receptor's flexural rigidity plays an important role in RME with clathrin. There is a threshold beyond which particle internalization will not occur. Without clathrin, it is very difficult to achieve complete endocytosis with ligand-receptor interactions alone. A shorter receptor length and longer ligand-receptor reaction cutoff promote the formation of ligand-receptor bonds and facilitate particle internalization. Complete internalization can only be obtained with an extremely short receptor length and long reaction cutoff. Therefore, there are most likely some additional mechanisms to drive the membrane deformation in clathrin-free RME. Our results yield important fundamental insights into RME and provide crucial guidance when correlating the simulation results with experimental observations.

A Frame-by-Frame Glance at Membrane Fusion Mechanisms: From Viral Infections to Fertilization

Viral entry and fertilization are distinct biological processes that share a common mechanism: membrane fusion. In viral entry, enveloped viruses attach to the host cell membrane, triggering a series of conformational changes in the viral fusion proteins. This results in the exposure of a hydrophobic fusion peptide, which inserts into the host membrane and brings the viral and host membranes into close proximity. Subsequent structural rearrangements in opposing membranes lead to their fusion. Similarly, membrane fusion occurs when gametes merge during the fertilization process, though the exact mechanism remains unclear. Structural biology has played a pivotal role in elucidating the molecular mechanisms underlying membrane fusion. High-resolution structures of the viral and fertilization fusion-related proteins have provided valuable insights into the conformational changes that occur during this process. Understanding these mechanisms at a molecular level is essential for the development of antiviral therapeutics and tools to influence fertility. In this review, we will highlight the biological importance of membrane fusion and how protein structures have helped visualize both common elements and subtle divergences in the mechanisms behind fusion; in addition, we will examine the new tools that recent advances in structural biology provide researchers interested in a frame-by-frame understanding of membrane fusion.

Maternal Diabetes Deregulates the Expression of Mecp2 via miR-26b-5p in Mouse Embryonic Neural Stem Cells

Maternal diabetes has been associated with a greater risk of neurodevelopmental disorders in offspring. It has been established that hyperglycemia alters the expression of genes and microRNAs (miRNAs) regulating the fate of neural stem cells (NSCs) during brain development. In this study, the expression of methyl-CpG-binding protein-2 (Mecp2), a global chromatin organizer and a crucial regulator of synaptic proteins, was analyzed in NSCs obtained from the forebrain of embryos of diabetic mice. Mecp2 was significantly downregulated in NSCs derived from embryos of diabetic mice when compared to controls. miRNA target prediction revealed that the miR-26 family could regulate the expression of Mecp2, and further validation confirmed that Mecp2 is a target of miR-26b-5p. Knockdown of Mecp2 or overexpression of miR-26b-5p altered the expression of tau protein and other synaptic proteins, suggesting that miR-26b-5p alters neurite outgrowth and synaptogenesis via Mecp2. This study revealed that maternal diabetes upregulates the expression of miR-26b-5p in NSCs, resulting in downregulation of its target, Mecp2, which in turn perturbs neurite outgrowth and expression of synaptic proteins. Overall, hyperglycemia dysregulates synaptogenesis that may manifest as neurodevelopmental disorders in offspring from diabetic pregnancy.

Cerebrospinal fluid biomarker panel of synaptic dysfunction in Alzheimer's disease and other neurodegenerative disorders

INTRODUCTION

Synaptic degeneration is a key part of the pathophysiology of neurodegenerative diseases, and biomarkers reflecting the pathological alterations are greatly needed.

METHOD

Seventeen synaptic proteins were quantified in a pathology-confirmed cerebrospinal fluid cohort of patients with Alzheimer's disease (AD; n = 63), frontotemporal lobar degeneration (FTLD; n = 53), and Lewy body spectrum of disorders (LBD; n = 21), as well as healthy controls (HC; n = 48).

RESULTS

Comparisons revealed four distinct patterns: markers decreased across all neurodegenerative conditions compared to HC (the neuronal pentraxins), markers increased across all neurodegenerative conditions (14-3-3 zeta/delta), markers selectively increased in AD compared to other neurodegenerative conditions (neurogranin and beta-synuclein), and markers selectively decreased in LBD and FTLD compared to HC and AD (AP2B1 and syntaxin-1B).

DISCUSSION

Several of the synaptic proteins may serve as biomarkers for synaptic dysfunction in AD, LBD, and FTLD. Additionally, differential patterns of synaptic protein alterations seem to be present across neurodegenerative diseases.

HIGHLIGHTS

A panel of synaptic proteins were quantified in the cerebrospinal fluid using mass spectrometry. We compared Alzheimer's disease, frontotemporal degeneration, and Lewy body spectrum of disorders. Pathology was confirmed by autopsy or familial mutations. We discovered synaptic biomarkers for synaptic degeneration and cognitive decline. We found differential patterns of synaptic proteins across neurodegenerative diseases.

Clathrin-dependent endocytosis plays a critical role in larval and pupal development, and female oocyte production in the red flour beetle (Tribolium castaneum)

BACKGROUND

Clathrin-dependent endocytosis is a vesicular transport process by which cells take macromolecules from the extracellular space to the intracellular space. It plays important roles in various cellular functions, but its biological significance in insect development and reproduction has not been well studied.

RESULTS

We characterized and functionally analyzed four major clathrin-dependent endocytic pathway genes (TcChc, TcAP50, TcVhaSFD, TcRab7) in Tribolium castaneum. RNA interference (RNAi) by injecting double-stranded RNA (dsRNA) targeting each gene at three doses (50, 100, or 200 ng per insect) in 20-day-old larvae led to 100% larval mortality. When the expressions of TcChc, TcVhaSFD, and TcRab7 were suppressed by injecting their respective dsRNAs at each dose in 1-day-old pupae, the adults that emerged from the dsRNA-injected pupae were deformed, with the absence of wing development. The deformed adults died within 2 days after eclosion. When the expression of TcAP50 was suppressed by injecting its dsRNA into 1-day-old pupae, although no apparent deformed adults were observed, all the adults died within 35 days after eclosion. In addition, when the expressions of TcChc and TcVhaSFD were suppressed by injecting their respective dsRNAs at a reduced dose (10 ng per insect) in 5-day-old pupae, the ovarian development and oocyte production in the resultant females were completely inhibited.

CONCLUSION

Our results indicate that clathrin-dependent endocytosis is essential for insect development and reproduction. The results from this study can help researchers identify potential molecular targets for developing novel strategies for insect pest management. © 2023 Society of Chemical Industry.

A conformational switch in clathrin light chain regulates lattice structure and endocytosis at the plasma membrane of mammalian cells

Conformational changes in endocytic proteins are regulators of clathrin-mediated endocytosis. Three clathrin heavy chains associated with clathrin light chains (CLC) assemble into triskelia that link into a geometric lattice that curves to drive endocytosis. Structural changes in CLC have been shown to regulate triskelia assembly in solution, yet the nature of these changes, and their effects on lattice growth, curvature, and endocytosis in cells are unknown. Here, we develop a new correlative fluorescence resonance energy transfer (FRET) and platinum replica electron microscopy method, named FRET-CLEM. With FRET-CLEM, we measure conformational changes in clathrin at thousands of individual morphologically distinct clathrin-coated structures. We discover that the N-terminus of CLC repositions away from the plasma membrane and triskelia vertex as coats curve. Preventing this conformational switch with chemical tools increases lattice sizes and inhibits endocytosis. Thus, a specific conformational switch in the light chain regulates lattice curvature and endocytosis in mammalian cells.

Clathrin light chain-conjugated drug delivery for cancer

Targeted drug delivery systems hold the remarkable potential to improve the therapeutic index of anticancer medications markedly. Here, we report a targeted delivery platform for cancer treatment using clathrin light chain (CLC)-conjugated drugs. We conjugated CLC to paclitaxel (PTX) through a glutaric anhydride at high efficiency. Labeled CLCs localized to 4T1 tumors implanted in mice, and conjugation of PTX to CLC enhanced its delivery to these tumors. Treatment of three different mouse models of cancer-melanoma, breast cancer, and lung cancer-with CLC-PTX resulted in significant growth inhibition of both the primary tumor and metastatic lesions, as compared to treatment with free PTX. CLC-PTX treatment caused a marked increase in apoptosis of tumor cells and reduction of tumor angiogenesis. Our data suggested HSP70 as a binding partner for CLC. Our study demonstrates that CLC-based drug-conjugates constitute a novel drug delivery platform that can augment the effects of chemotherapeutics in treating a variety of cancers. Moreover, conjugation of therapeutics with CLC may be used as means by which drugs are delivered specifically to primary tumors and metastatic lesions, thereby prolonging the survival of cancer patients.

Characteristics of environmental RNAi in potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Psylloidea: Triozidae)

RNA interference (RNAi) has potential to become a major tool for integrated management of insect pests of agricultural crops based on sequence-specificity and low doses of rapidly biodegradable dsRNA. Deploying ‘environmental RNAi’ for control of insect vectors of plant pathogens is of increasing interest for combatting emerging plant diseases. Hemipteran insect vectors, including psyllids, are vascular feeders, making their development difficult to control specifically by targeting with pesticidal chemistries. Psyllids transmit “Candidatus Liberibacter solanacearum” the causal organism of potato zebra chip and tomato vein greening diseases, transmitted, respectively, by the potato or tomato psyllid (PoP). Until now, the optimal effective concentration(s) of double-stranded RNA (dsRNA) required for significant gene knockdown and RNAi persistence in PoP have not been determined. The objective of this study was to optimize RNAi in young PoP adults and 3rd instars for screening by oral delivery of dsRNAs. The minimal effective dsRNA concentrations required for robust knockdown and persistence were evaluated by delivering seven concentrations spanning 0.1 ng/μL to 500 ng/μL over post ingestion-access periods (IAP) ranging from 48 h to 12 days. The PoP gene candidates evaluated as targets were vacuolar ATPase subunit A, clathrin heavy chain, and non-fermenting protein 7, which were evaluated for knockdown by qPCR amplification. The minimum and/or the second most effective dsRNA concentration resulting in effective levels of gene knockdown was 100 ng/μL for all three targets. Higher concentrations did not yield further knockdown, indicating potential RISC saturation at the higher doses. Gene silencing post-IAP of 100 ng/μL dsRNA persisted for 3–5 days in adults and nymphs, with the PoP 3rd instar, followed by teneral and mature adults, respectively, exhibiting the most robust RNAi-response.

Functional Diversity of Macropinocytosis

Eukaryotic cells are capable of internalizing different types of cargo by plasma membrane ruffling and forming vesicles in a process known as endocytosis. The most extensively characterized endocytic pathways are clathrin-coated pits, lipid raft/caveolae-mediated endocytosis, phagocytosis, and macropinocytosis. Macropinocytosis is unique among all the endocytic processes due to its nonselective internalization of extracellular fluid, solutes, and membrane in large endocytic vesicles known as macropinosomes with unique susceptibility toward Na+/H+ exchanger inhibitors. Range of cell types capable of macropinocytosis and known to play important role in different physiological processes, which include antigen presentation, nutrient sensing, migration, and signaling. Understanding the physiological function of macropinocytosis will be helpful in filling the gaps in our knowledge and which can be exploited to develop novel therapeutic targets. In this chapter, we discuss the different molecular mechanisms that initiate the process of macropinocytosis with special emphasis on proteins involved and their diversified role in different cell types.

Clathrin-nanoparticles deliver BDNF to hippocampus and enhance neurogenesis, synaptogenesis and cognition in HIV/neuroAIDS mouse model

Brain derived neurotrophic factor (BDNF) promotes the growth, differentiation, maintenance and survival of neurons. These attributes make BDNF a potentially powerful therapeutic agent. However, its charge, instability in blood, and poor blood brain barrier (BBB) penetrability have impeded its development. Here, we show that engineered clathrin triskelia (CT) conjugated to BDNF (BDNF-CT) and delivered intranasally increased hippocampal BDNF concentrations 400-fold above that achieved previously with intranasal BDNF alone. We also show that BDNF-CT targeted Tropomyosin receptor kinase B (TrkB) and increased TrkB expression and downstream signaling in iTat mouse brains. Mice were induced to conditionally express neurotoxic HIV Transactivator-of-Transcription (Tat) protein that decreases BDNF. Down-regulation of BDNF is correlated with increased severity of HIV/neuroAIDS. BDNF-CT enhanced neurorestorative effects in the hippocampus including newborn cell proliferation and survival, granule cell neurogenesis, synaptogenesis and increased dendritic integrity. BDNF-CT exerted cognitive-enhancing effects by reducing Tat-induced learning and memory deficits. These results show that CT bionanoparticles efficiently deliver BDNF to the brain, making them potentially powerful tools in regenerative medicine.

Role of Clathrin and Dynamin in Clathrin Mediated Endocytosis/Synaptic Vesicle Recycling and Implications in Neurological Diseases

Endocytosis is a process essential to the health and well-being of cell. It is required for the internalisation and sorting of “cargo”—the macromolecules, proteins, receptors and lipids of cell signalling. Clathrin mediated endocytosis (CME) is one of the key processes required for cellular well-being and signalling pathway activation. CME is key role to the recycling of synaptic vesicles [synaptic vesicle recycling (SVR)] in the brain, it is pivotal to signalling across synapses enabling intracellular communication in the sensory and nervous systems. In this review we provide an overview of the general process of CME with a particular focus on two key proteins: clathrin and dynamin that have a central role to play in ensuing successful completion of CME. We examine these two proteins as they are the two endocytotic proteins for which small molecule inhibitors, often of known mechanism of action, have been identified. Inhibition of CME offers the potential to develop therapeutic interventions into conditions involving defects in CME. This review will discuss the roles and the current scope of inhibitors of clathrin and dynamin, providing an insight into how further developments could affect neurological disease treatments.

Clathrin light chains regulate hypocotyl elongation by affecting the polarization of the auxin transporter PIN3 in Arabidopsis

PIN-FORMED (PIN)-dependent directional auxin transport is crucial for plant development. Although the redistribution of auxin mediated by the polarization of PIN3 plays key roles in modulating hypocotyl cell expansion, how PIN3 becomes repolarized to the proper sites within hypocotyl cells is poorly understood. We previously generated the clathrin light chain clc2-1 clc3-1 double mutant in Arabidopsis thaliana and found that it has an elongated hypocotyl phenotype compared to the wild type. Here, we performed genetic, cell biology, and pharmacological analyses combined with live-cell imaging to elucidate the molecular mechanism underlying the role of clathrin light chains in hypocotyl elongation. Our analyses indicated that the defects of the double mutant enhanced auxin maxima in epidermal cells, thus, promoting hypocotyl elongation. PIN3 relocated to the lateral sides of hypocotyl endodermal cells in clc2-1 clc3-1 mutants to redirect auxin toward the epidermal cell layers. Moreover, the loss of function of PIN3 largely suppressed the long hypocotyl phenotype of the clc2-1 clc3-1 double mutant, as did treatment with auxin transport inhibitors. Based on these data, we propose that clathrin modulates PIN3 abundance and polarity to direct auxin flux and inhibit cell elongation in the hypocotyl, providing novel insights into the regulation of hypocotyl elongation.

Designed Antitumor Peptide for Targeted siRNA Delivery into Cancer Spheroids

Antimicrobial/anticancer peptides (AMPs/ACPs) have shown promising results as new therapeutic agents in cancer thearpy. Among them, the designed amphiphilic α-helical peptide G(IIKK)₃I-NH₂ (G3) displayed great affinity and specificity in targeting cancer cells. Here, we report new insights on how G3 penetrates cancer cells. G3 showed high specificity to HCT-116 colon cancer cells compared to the HDFs (human neonatal primary dermal fibroblasts) control. With high concentrations of peptide, a clear cancer cell membrane disruption was observed through SEM. Gene knockdown of the endocytic pathways demonstrated that an energy-dependent endocytic pathway is required for the uptake of the peptide. In addition, G3 can protect and selectively deliver siRNAs into cancer cells and successfully modulated their gene expression. Gene delivery was also tested in 3D cancer spheroids and showed deep penetration delivery into the cancer spheroids. Finally, the in vivo toxicity of G3 was evaluated on zebrafish embryos, showing an increasing toxicity effect with concentration. However, the toxicity of the peptide was attenuated when complexed with siRNA. In addition, negligible toxicity was observed at the concentration range for efficient gene delivery. The current results demonstrate that G3 is promising as an excellent agent for cancer therapy.

Therapeutic potential of garlic chive-derived vesicle-like nanoparticles in NLRP3 inflammasome-mediated inflammatory diseases

Aberrant activation of the nucleotide-binding domain and leucine-rich repeat related (NLR) family, pyrin domain containing 3 (NLRP3) inflammasome drives the development of many complex inflammatory diseases, such as obesity, Alzheimer's disease, and atherosclerosis. However, no medications specifically targeting the NLRP3 inflammasome have become clinically available. Therefore, we aim to identify new inhibitors of the NLRP3 inflammasome in this study. Methods: Vesicle-like nanoparticles (VLNs) were extracted from garlic chives and other Allium vegetables and their effects on the NLRP3 inflammasome were evaluated in primary macrophages. After garlic chive-derived VLNs (GC-VLNs) were found to exhibit potent anti-NLRP3 inflammasome activity in cell culture, such function was further assessed in a murine acute liver injury disease model, as well as in diet-induced obesity. Finally, GC-VLNs were subjected to omics analysis to identify the active components with anti-NLRP3 inflammasome function. Results: GC-VLNs are membrane-enclosed nanoparticles containing lipids, proteins, and RNAs. They dose-dependently inhibit pathways downstream of NLRP3 inflammasome activation, including caspase-1 autocleavage, cytokine release, and pyroptotic cell death in primary macrophages. The inhibitory effects of GC-VLNs on the NLRP3 inflammasome are specific, considering their marginal impact on activation of other inflammasomes. Local administration of GC-VLNs in mice alleviates NLRP3 inflammasome-mediated inflammation in chemical-induced acute liver injury. When administered orally or intravenously, GC-VLNs accumulate in specific tissues and suppress activation of the NLRP3 inflammasome and chronic inflammation in diet-induced obese mice. The phospholipid 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLPC) in GC-VLNs has been identified to inhibit NLRP3 inflammasome activation. Conclusions: Identification of GC-VLNs and their active component DLPC as potent inflammasome inhibitors provides new therapeutic candidates in the treatment of NLRP3 inflammasome-driven diseases.

Investigating the molecular mechanisms of learning and memory using Caenorhabditis elegans

Learning is an essential biological process for survival since it facilitates behavioural plasticity in response to environmental changes. This process is mediated by a wide variety of genes, mostly expressed in the nervous system. Many studies have extensively explored the molecular and cellular mechanisms underlying learning and memory. This review will focus on the advances gained through the study of the nematode Caenorhabditis elegans. C. elegans provides an excellent system to study learning because of its genetic tractability, in addition to its invariant, compact nervous system (~300 neurons) that is well-characterised at the structural level. Importantly, despite its compact nature, the nematode nervous system possesses a high level of conservation with mammalian systems. These features allow the study of genes within specific sensory-, inter- and motor neurons, facilitating the interrogation of signalling pathways that mediate learning via defined neural circuits. This review will detail how learning and memory can be studied in C. elegans through behavioural paradigms that target distinct sensory modalities. We will also summarise recent studies describing mechanisms through which key molecular and cellular pathways are proposed to affect associative and non-associative forms of learning.

Clathrin Is Important for Virulence Factors Delivery in the Necrotrophic Fungus Botrytis cinerea

Fungi are the most prevalent plant pathogens, causing annually important damages. To infect and colonize their hosts, they secrete effectors including hydrolytic enzymes able to kill and macerate plant tissues. These secreted proteins are transported from the Endoplasmic Reticulum and the Golgi apparatus to the extracellular space through intracellular vesicles. In pathogenic fungi, intracellular vesicles were described but their biogenesis and their role in virulence remain unclear. In this study, we report the essential role of clathrin heavy chain (CHC) in the pathogenicity of Botrytis cinerea, the agent of gray mold disease. To investigate the importance of this protein involved in coat vesicles formation in eukaryotic cells, a T-DNA insertional mutant reduced in the expression of the CHC-encoding gene, and a mutant expressing a dominant-negative form of CHC were studied. Both mutants were strongly affected in pathogenicity. Characterization of the mutants revealed altered infection cushions and an important defect in protein secretion. This study demonstrates the essential role of clathrin in the infectious process of a plant pathogenic fungus and more particularly its role in virulence factors delivery.

An integrative view on vacuolar pH homeostasis in Arabidopsis thaliana: Combining mathematical modeling and experimentation

The acidification of plant vacuoles is of great importance for various physiological processes, as a multitude of secondary active transporters utilize the proton gradient established across the vacuolar membrane. Vacuolar-type H⁺ -translocating ATPases and a pyrophosphatase are thought to enable vacuoles to accumulate protons against their electrochemical potential. However, recent studies pointed to the ATPase located at the trans-Golgi network/early endosome (TGN/EE) to contribute to vacuolar acidification in a manner not understood as of now. Here, we combined experimental data and computational modeling to test different hypotheses for vacuolar acidification mechanisms. For this, we analyzed different models with respect to their ability to describe existing experimental data. To better differentiate between alternative acidification mechanisms, new experimental data have been generated. By fitting the models to the experimental data, we were able to prioritize the hypothesis in which vesicular trafficking of Ca²⁺ /H⁺ -antiporters from the TGN/EE to the vacuolar membrane and the activity of ATP-dependent Ca²⁺ -pumps at the tonoplast might explain the residual acidification observed in Arabidopsis mutants defective in vacuolar proton pump activity. The presented modeling approach provides an integrative perspective on vacuolar pH regulation in Arabidopsis and holds potential to guide further experimental work.

Cerebrospinal fluid biomarker panel for synaptic dysfunction in Alzheimer's disease

INTRODUCTION

Synaptic dysfunction and degeneration is one of the earliest events in Alzheimer's disease (AD) and the best correlate of cognitive decline. Thus, identification and validation of biomarkers reflecting synaptic degeneration to be used as prognostic biomarkers are greatly needed.

METHOD

Solid-phase extraction and parallel reaction monitoring mass spectrometry were used to quantify 17 synaptic proteins in CSF, in two cross-sectional studies including AD (n = 52) and controls (n = 37).

RESULTS

Increased concentrations of beta-synuclein, gamma-synuclein, neurogranin, phosphatidylethanolamine-binding protein 1, and 14-3-3 proteins were observed in AD patients compared to controls, while neuronal pentraxin-2 and neuronal pentraxin receptor were decreased.

DISCUSSION

We have established a method with a novel panel of synaptic proteins as biomarkers of synaptic dysfunction. The results indicate that several of the proteins included in the panel may serve as synaptic biomarkers for AD.

Wbox2: A clathrin terminal domain-derived peptide inhibitor of clathrin-mediated endocytosis

Clathrin-mediated endocytosis (CME) occurs via the formation of clathrin-coated vesicles from clathrin-coated pits (CCPs). Clathrin is recruited to CCPs through interactions between the AP2 complex and its N-terminal domain, which in turn recruits endocytic accessory proteins. Inhibitors of CME that interfere with clathrin function have been described, but their specificity and mechanisms of action are unclear. Here we show that overexpression of the N-terminal domain with (TDD) or without (TD) the distal leg inhibits CME and CCP dynamics by perturbing clathrin interactions with AP2 and SNX9. TDD overexpression does not affect clathrin-independent endocytosis or, surprisingly, AP1-dependent lysosomal trafficking from the Golgi. We designed small membrane–permeant peptides that encode key functional residues within the four known binding sites on the TD. One peptide, Wbox2, encoding residues along the W-box motif binding surface, binds to SNX9 and AP2 and potently and acutely inhibits CME.

A draft phased assembly of the diploid Cascade hop (Humulus lupulus) genome

Hop (Humulus lupulus L. var Lupulus) is a diploid, dioecious plant with a history of cultivation spanning more than one thousand years. Hop cones are valued for their use in brewing and contain compounds of therapeutic interest including xanthohumol. Efforts to determine how biochemical pathways responsible for desirable traits are regulated have been challenged by the large (2.8 Gb), repetitive, and heterozygous genome of hop. We present a draft haplotype-phased assembly of the Cascade cultivar genome. Our draft assembly and annotation of the Cascade genome is the most extensive representation of the hop genome to date. PacBio long-read sequences from hop were assembled with FALCON and partially phased with FALCON-Unzip. Comparative analysis of haplotype sequences provides insight into selective pressures that have driven evolution in hop. We discovered genes with greater sequence divergence enriched for stress-response, growth, and flowering functions in the draft phased assembly. With improved resolution of long terminal retrotransposons (LTRs) due to long-read sequencing, we found that hop is over 70% repetitive. We identified a homolog of cannabidiolic acid synthase (CBDAS) that is expressed in multiple tissues. The approaches we developed to analyze the draft phased assembly serve to deepen our understanding of the genomic landscape of hop and may have broader applicability to the study of other large, complex genomes.

Identification of anti-inflammatory vesicle-like nanoparticles in honey

Honey has been used as a nutrient, an ointment, and a medicine worldwide for many centuries. Modern research has demonstrated that honey has many medicinal properties, reflected in its anti-microbial, anti-oxidant, and anti-inflammatory bioactivities. Honey is composed of sugars, water and a myriad of minor components, including minerals, vitamins, proteins and polyphenols. Here, we report a new bioactive component‒vesicle-like nanoparticles‒in honey (H-VLNs). These H-VLNs are membrane-bound nano-scale particles that contain lipids, proteins and small-sized RNAs. The presence of plant-originated plasma transmembrane proteins and plasma membrane-associated proteins suggests the potential vesicle-like nature of these particles. H-VLNs impede the formation and activation of the nucleotide-binding domain and leucine-rich repeat related (NLR) family, pyrin domain containing 3 (NLRP3) inflammasome, which is a crucial inflammatory signalling platform in the innate immune system. Intraperitoneal administration of H-VLNs in mice alleviates inflammation and liver damage in the experimentally induced acute liver injury. miR-4057 in H-VLNs was identified in inhibiting NLRP3 inflammasome activation. Together, our studies have identified anti-inflammatory VLNs as a new bioactive agent in honey.

His-Mediated Reversible Self-Assembly of Ferritin Nanocages through Two Different Switches for Encapsulation of Cargo Molecules

Protein nanocages represent a class of nanovehicles for a variety of applications. However, precise manipulation of self-assembly behavior of these protein nanocages in response to multiple external stimuli for custom-tailored applications remains challenging. Herein, we established a simple but effective strategy for controlling protein nanocage self-assembly that combines a dual property of His motifs (their significantly pH-dependent protonation state and their capacity to coordinate with transition metals) with its high symmetry. With this strategy, we enabled two different ferritin nanocages to disassemble into protein tetramers under neutral solution by introducing His₆ motifs at the 4-fold channel interfaces. Notably, these tetramers are able to self-assemble into ferritin-like protein nanocages in response to multiple external stimuli such as transition metal ions and pH, and vice versa, indicative of a reversible self-assembly process. Furthermore, such His-mediated reversible protein self-assembly has been explored for encapsulation of bioactive cargo molecules within these reconstituted protein nanocages with higher loading efficiency under milder conditions as compared to the reported acid denaturation encapsulation method for ferritin.

Tailoring Iron Oxide Nanoparticles for Efficient Cellular Internalization and Endosomal Escape

Iron oxide nanoparticles (IONs) have been widely explored for biomedical applications due to their high biocompatibility, surface-coating versatility, and superparamagnetic properties. Upon exposure to an external magnetic field, IONs can be precisely directed to a region of interest and serve as exceptional delivery vehicles and cellular markers. However, the design of nanocarriers that achieve an efficient endocytic uptake, escape lysosomal degradation, and perform precise intracellular functions is still a challenge for their application in translational medicine. This review highlights several aspects that mediate the activation of the endosomal pathways, as well as the different properties that govern endosomal escape and nuclear transfection of magnetic IONs. In particular, we review a variety of ION surface modification alternatives that have emerged for facilitating their endocytic uptake and their timely escape from endosomes, with special emphasis on how these can be manipulated for the rational design of cell-penetrating vehicles. Moreover, additional modifications for enhancing nuclear transfection are also included in the design of therapeutic vehicles that must overcome this barrier. Understanding these mechanisms opens new perspectives in the strategic development of vehicles for cell tracking, cell imaging and the targeted intracellular delivery of drugs and gene therapy sequences and vectors.

Presynaptic dysfunction in neurodevelopmental disorders: Insights from the synaptic vesicle life cycle

The activity-dependent fusion, retrieval and recycling of synaptic vesicles is essential for the maintenance of neurotransmission. Until relatively recently it was believed that most mutations in genes that were essential for this process would be incompatible with life, because of this fundamental role. However, an ever-expanding number of mutations in this very cohort of genes are being identified in individuals with neurodevelopmental disorders, including autism, intellectual disability and epilepsy. This article will summarize the current state of knowledge linking mutations in presynaptic genes to neurodevelopmental disorders by sequentially covering the various stages of the synaptic vesicle life cycle. It will also discuss how perturbations of specific stages within this recycling process could translate into human disease. Finally, it will also provide perspectives on the potential for future therapy that are targeted to presynaptic function.

Sulfated syndecan 1 is critical to preventing cellular senescence by modulating fibroblast growth factor receptor endocytosis

Cellular senescence can be triggered by various intrinsic and extrinsic stimuli. We previously reported that silencing of 3'-phosphoadenosine 5'-phosphosulfate synthetase 2 (PAPSS2) induces cellular senescence through augmented fibroblast growth factor receptor 1 (FGFR1) signaling. However, the exact molecular mechanism connecting heparan sulfation and cellular senescence remains unclear. Here, we investigated the potential involvement of heparan sulfate proteoglycans (HSPGs) in augmented FGFR1 signaling and cellular senescence. Depletion of several types of HSPGs revealed that cells depleted of syndecan 1 (SDC1) exhibited typical senescence phenotypes, and those depleted of PAPSS2-, SDC1-, or heparan sulfate 2-O sulfotransferase 1 (HS2ST1) showed decreased FGFR1 internalization along with hyperresponsiveness to and prolonged activation of fibroblast growth factor 2 (FGF2)-stimulated FGFR1- v-akt murine thymoma viral oncogene homolog (AKT) signaling. Clathrin- and caveolin-mediated FGFR1 endocytosis contributed to cellular senescence through the FGFR1-AKT-p53-p21 signaling pathway. Dynasore treatment triggered senescence phenotypes, augmented FGFR1-AKT-p53-p21 signaling, and decreased SDC1 expression. Finally, the replicatively and prematurely senescent cells were characterized by decreases of SDC1 expression and FGFR1 internalization, and an increase in FGFR1-AKT-p53-p21 signaling. Together, our results demonstrate that properly sulfated SDC1 plays a critical role in preventing cellular senescence through the regulation of FGFR1 endocytosis.

Different localization of lysosomal-associated membrane protein 1 (LAMP1) in mammalian cultured cell lines

Lysosomal-associated membrane protein 1 (LAMP1) mainly localizes to lysosomes and late endosomes. We herein investigated the intracellular localization of lysosomal membrane proteins in five mammalian cultured cell lines. Rat LAMP1 fused to enhanced green fluorescent protein (EGFP) mostly accumulated at a particular cytoplasmic area and barely co-localized with LysoTracker® Red DND-99 in golden hamster kidney BHK-21 cells and Chinese hamster ovary CHO-K1 cells. Golden hamster, Chinese hamster, and human LAMP1-EGFP showed a similar intracellular distribution to rat LAMP1-EGFP in BHK-21 cells. Endogenous LAMP1 was also detected in a perinuclear area in BHK-21 cells and CHO-K1 cells, and co-localized with rat CD63-EGFP in BHK-21 cells. Moreover, rat LAMP1-DsRed-Monomer co-localized well with the human trans-Golgi network protein 2-EGFP in BHK-21 cells. These results reveal that LAMP1 predominantly localizes to the trans-Golgi network in BHK-21 cells.

Integrated Transcriptomics, Proteomics, and Glycomics Reveals the Association between Up-regulation of Sialylated N-glycans/Integrin and Breast Cancer Brain Metastasis

Breast cancer brain metastasis has been recognized as one of the central issues in breast cancer research. The elucidation of the processes and pathways that mediate this step will provide important clues for a better understanding of breast cancer metastasis. Increasing evidence suggests that aberrant glycosylation patterns greatly contribute to cell invasion and cancer metastasis. Herein, we combined next-generation RNA sequencing with liquid chromatography-tandem mass spectrometry-based proteomic and N-glycomic analysis from five breast cancer cell lines and one brain cancer cell line to investigate the possible mechanisms of breast cancer brain metastasis. The genes/proteins associated with cell movement were highlighted in breast cancer brain metastasis. The integrin signaling pathway and the up-regulation of α-integrin (ITGA2, ITGA3) were associated with the brain metastatic process. 12 glycogenes showed unique expression in 231BR, which could result in an increase of sialylation during brain metastasis. In agreement with the changes of glycogenes, 60 out of 63 N-glycans that were identified exhibited differential expression among cell lines. The correlation between glycogenes and glycans revealed the importance of sialylation and sialylated glycans in breast cancer brain metastasis. Highly sialylated N-glycans, which were up-regulated in brain-seeking cell line 231BR, likely play a role in brain metastasis.

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.

Identification of clathrin proteins by incorporating hyperparameter optimization in deep learning and PSSM profiles

BACKGROUND AND OBJECTIVES

Clathrin is an adaptor protein that serves as the principal element of the vesicle-coating complex and is important for the membrane cleavage to dispense the invaginated vesicle from the plasma membrane. The functional loss of clathrins has been tied to a lot of human diseases, i.e., neurodegenerative disorders, cancer, Alzheimer's diseases, and so on. Therefore, creating a precise model to identify its functions is a crucial step towards understanding human diseases and designing drug targets.

METHODS

We present a deep learning model using a two-dimensional convolutional neural network (CNN) and position-specific scoring matrix (PSSM) profiles to identify clathrin proteins from high throughput sequences. Traditionally, the 2D CNNs take images as an input so we treated the PSSM profile with a 20 × 20 matrix as an image of 20 × 20 pixels. The input PSSM profile was then connected to our 2D CNN in which we set a variety of parameters to improve the performance of the model. Based on the 10-fold cross-validation results, hyper-parameter optimization process was employed to find the best model for our dataset. Finally, an independent dataset was used to assess the predictive ability of the current model.

RESULTS

Our model could identify clathrin proteins with sensitivity of 92.2%, specificity of 91.2%, accuracy of 91.8%, and MCC of 0.83 in the independent dataset. Compared to state-of-the-art traditional neural networks, our method achieved a significant improvement in all typical measurement metrics.

CONCLUSIONS

Throughout the proposed study, we provide an effective tool for investigating clathrin proteins and our achievement could promote the use of deep learning in biomedical research. We also provide source codes and dataset freely at https://www.github.com/khanhlee/deep-clathrin/.

Design and site-directed compartmentalization of gold nanoclusters within the intrasubunit interfaces of ferritin nanocage

Background

Protein nanocages have emerged as popular nanocarriers for either drug delivery or biotemplates for the preparation of nanomaterials. However, only three interfaces, namely exterior surface, intersubunit and inner cavity, have been used as reaction sites for the above purposes with all known protein nanocages. On the other hand, how to control the site of Au NCs formed within a targeted protein template while maintaining the functionality of protein itself remains challenging.

Results

In this work, inspired by compartmentalization in living systems, we firstly come up with the conception of “intrasubunit interfaces”, located within subunit of protein nanocage. We built a new, specific compartment for fabrication of gold nanoclusters by genetic modification of the inherent ferroxidase center located within four-α-helix bundle of each ferritin subunit. This newly built compartment not only realizes the site-directed synthesis of gold nanoclusters but also has no effect on the functionality of ferritin itself such as encapsulation by its inner cavity. These redesigned composites can be further applied as fluorescent imaging agent and carriers for preparation of hybrid nanomaterials.

Conclusions

The designing strategy of intrasubunit interfaces opens a new way for future applications of cage-like proteins.

Electronic supplementary material

The online version of this article (10.1186/s12951-019-0512-0) contains supplementary material, which is available to authorized users.

Association of AEBP1 and NRN1 RNA expression with Alzheimer's disease and neurofibrillary tangle density in middle temporal gyrus

We explored RNA expression changes in the middle temporal gyrus (MTG) of Alzheimer's Disease patients (AD) by RNA sequencing the whole transcriptome of 8 AD and 8 Non-Demented (ND) controls. We used three additional expression datasets from related brain regions to validate the findings. The results highlighted the upregulation of AEBP1 and downregulation of NRN1 in AD, as well as their association with Braak staging and neurofibrillary tangles density. Furthermore, more than 400 protein-coding RNAs enriched for "Clathrin-mediated endocytosis" were validated in independent datasets from the same brain region. Finally, using in silico prediction analysis we found a signature of 52 non-protein coding RNAs that perturb key pathways involved in GABAergic transmission and peptide chain elongation. The association of AEBP1 in our data confirmed other published work examining gene expression in the hippocampus of AD patients. NRN1 is involved in neurite outgrowth, and in previous studies it has been shown to reverse synaptic defects and cognitive function impairment in Tg2576 mice. Finally, our results on non-protein coding RNAs suggest a role of these transcripts in altering synaptic and amyloid-β associated pathways.

Measuring Clathrin-Coated Vesicle Formation with Single-Molecule Resolution

High-resolution fluorescence microscopy is increasingly contributing to our understanding of molecular processes. By utilizing single-molecule intensity information, imaging experiments can be rendered quantitative, yielding insights into the stoichiometry and kinetics of the components of a molecular assembly. Here, we describe the experimental and analytical steps needed to study the assembly of clathrin-coated vesicles with single-molecule resolution, using total internal reflection fluorescence microscopy. Many components of the protocol are broadly applicable to the characterization of other molecular processes.

Co-Encapsulation and Co-Delivery of Peptide Drugs via Polymeric Nanoparticles

Combination therapy is a promising form of treatment. In particular, co-treatment of P3 and QBP1 has been shown to enhance therapeutic effect in vivo in treating polyglutamine diseases. These peptide drugs, however, face challenges in clinical administration due to poor stability, inability to reach intracellular targets, and lack of method to co-deliver both drugs. Here we demonstrate two methods of co-encapsulating the peptide drugs via polymer poly(ethylene glycol)-block-polycaprolactone (PEG-b-PCL) based nanoparticles. Nanoparticles made by double emulsion were 100⁻200 nm in diameter, with drug encapsulation efficiency of around 30%. Nanoparticles made by nanoprecipitation with lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (POPG) were around 250⁻300 nm in diameter, with encapsulation efficiency of 85⁻100%. Particles made with both formulations showed cellular uptake when decorated with a mixture of peptide ligands that facilitate endocytosis. In vitro assay showed that nanoparticles could deliver bioactive peptides and encapsulation by double emulsion were found to be more effective in rescuing cells from polyglutamine-induced toxicity.

Disulfide-mediated reversible two-dimensional self-assembly of protein nanocages

Disulfide-mediated 2D protein self-assembly was achieved by single point mutation of hot spots at the C₄ interface of ferritin.

Thermostability of protein nanocages: the effect of natural extra peptide on the exterior surface

Protein nanocages have been used as functional bio-templates for the synthesis or organization of nanomaterials. However, the stability of these protein nanocages is nonideal, which limits their applications. Herein, we characterized the high thermal stability of plant ferritin, soybean seed H-2 ferritin (SSFH-2), the melting point (T_m) of which is 106 °C. We demonstrated that the hyperthermostability of SSFH-2 is derived from extra peptides (EP) located on its outer surface. Indeed, removal of the EP domains resulted in a dramatic decrease in T_m to 88 °C. Similar to EP-deleted plant ferritin, human H-chain ferritin (HuHF) has a T_m of 82 °C. Excitingly, the graft of the EP domain on the exterior surface of HuHF pronouncedly improved its T_m to 103 °C, which represents a simple, efficient approach to the construction of protein architectures with high stability. The remarkable stability of protein nanocages will greatly facilitate their application as robust biotemplates in the field of nanoscience.

Ferritin nanocage exhibits hyperthermostability with EP domain located on its outer surface.

The physiology of impenetrable skin: Colossus of the X-Men

The X-Men are an ensemble of superheroes whose powers are associated with the X-Gene, a mutant genetic factor. The powers exhibited by each character differ and are dependent on how the X-Gene has modified their individual genomes. For instance, Wolverine possesses regenerative healing, Storm can control local weather systems, and Colossus can create an impenetrable "organic steel" layer around his body. Thanks to the establishment of the superhero genre in modern cinema, audiences are familiar with Colossus from films such as X-Men: Days of Future Past and Deadpool. While attaining this power might be attractive to many people, there are innumerate scientific obstacles to be overcome to replicate this "organic steel" layer. Due to its unique combination of high strength and flexibility, a graphene-based layer might be a more realistic material for Colossus' impenetrable skin and would also address a number of physiological issues associated with an "organic steel" layer. The actualization of this layer would depend on complex processes associated with protein folding, protein self-assembly, and changing the structure of his skin. In the classroom, Colossus can foster a multidisciplinary learning environment where concepts in physiology can overlap with topics in physics, engineering, and materials science. Just like other superheroes, Colossus can also be used to promote scientific content in outreach for the general public.

On-Axis Alignment of Protein Nanocage Assemblies from 2D to 3D through the Aromatic Stacking Interactions of Amino Acid Residues

Aromatic-aromatic interactions between natural aromatic amino acids Phe, Tyr, and Trp play crucial roles in protein-protein recognition and protein folding. However, the function of such interactions in the preparation of different dimensional, ordered protein superstructures has not been recognized. Herein, by a combination of the directionality of the symmetry axes of protein building blocks and the strength of the aromatic-aromatic interactions coming from a group of aromatic amino acid residues, we built an engineering strategy to construct protein superlattices. Based on this strategy, substitution of single amino acid residue Glu162 around the C₄ rotation axes near the outer surface of 24-mer ferritin nanocage with Phe, Tyr, and Trp, respectively, resulted in 2D and 3D protein superlattices where protein cages are aligned along the C₄ axes, imposing a fixed disposition of neighboring ferritins. The self-assembly of these superlattices is reversible, which can be tuned by external stimuli (salt concentration or pH). Moreover, these superlattices can serve as biotemplates for the fabrication of 2D and 3D inorganic nanoparticle arrays.

Survivin inhibits excessive autophagy in cancer cells but does so independently of its interaction with LC3

Survivin expression is pivotal to life and death at the cellular level. For the past decade its pro-survival activity has been attributed to its essential role in cell proliferation and its ability to inhibit apoptosis. However, a growing body of evidence suggests that it may also contribute to cell viability through an as yet undefined role in autophagy. We report that survivin overexpression in osteosarcoma (U2OS) cells is associated with increased LC3-II expression, smaller autophagosomes, enlarged lysosomes and reduced autophagic flux. We also demonstrate that survivin binds LC3 directly through a canonical LC3-interacting region (LIR) in its baculovirus inhibitors of apoptosis protein (IAP) repeat BIR domain, mutation of which inhibits the interaction, but does not abrogate its influence on autophagy. Collectively these data suggest that survivin expression restricts autophagic flux, thereby inhibiting late-stage autophagy and preventing cell death, but does so independently of LC3.

Summary: Survivin binds to LC3 through a canonical LIR, yet this interaction is not required for survivin overexpression to reduce autophagic flux, suggesting that survivin regulates autophagy via an alternative mechanism.

Iron overload by transferrin receptor protein 1 regulation plays an important role in palmitate-induced insulin resistance in human skeletal muscle cells

Free fatty acid is considered to be one of the major pathogenic factors of inducing insulin resistance. The association between iron disturbances and insulin resistance has recently begun to receive a lot of attention. Although skeletal muscles are a major tissue for iron utilization and storage, the role of iron in palmitate (PA)-induced insulin resistance is unknown. We investigated the molecular mechanism underlying iron dysregulation in PA-induced insulin resistance. Interestingly, we found that PA simultaneously increased intracellular iron and induced insulin resistance. The iron chelator deferoxamine dramatically inhibited PA-induced insulin resistance, and iron donors impaired insulin sensitivity by activating JNK. PA up-regulated transferrin receptor 1 (tfR1), an iron uptake protein, which was modulated by iron-responsive element-binding proteins 2. Knockdown of tfR1 and iron-responsive element-binding proteins 2 prevented PA-induced iron uptake and insulin resistance. PA also translocated the tfR1 by stimulating calcium influx, but the calcium chelator, BAPTA-AM, dramatically reduced iron overload by inhibiting tfR1 translocation and ultimately increased insulin sensitivity. Iron overload may play a critical role in PA-induced insulin resistance. Blocking iron overload may thus be a useful strategy for preventing insulin resistance and diabetes.-Cui, R., Choi, S.-E., Kim, T. H., Lee, H. J., Lee, S. J., Kang, Y., Jeon, J. Y., Kim, H. J., Lee, K.-W. Iron overload by transferrin receptor protein 1 regulation plays an important role in palmitate-induced insulin resistance in human skeletal muscle cells.

Erythrocyte-Derived Optical Nanoprobes Doped with Indocyanine Green-Bound Albumin: Material Characteristics and Evaluation for Cancer Cell Imaging

Nanosize structures activated by near-infrared (NIR) photoexcitation can provide an optical platform for the image-guided removal of small tumor nodules. We have engineered nanoparticles derived from erythrocytes that can be doped with NIR fluorophore indocyanine green (ICG). We refer to these constructs as NIR erythrocyte-derived transducers (NETs). The objective of this study was to determine if ICG-bound albumin (IbA), as the doping material, could enhance the fluorescence emission of NETs, and evaluate the capability of these nanoprobes in imaging cancer cells. Erythrocytes were isolated from bovine whole blood and depleted of hemoglobin to form erythrocyte ghosts (EGs). EGs were then extruded through nanosize porous membranes in the presence of 10-100 μm ICG or Iba (1:1 molar ratio) to form ICG- or IbA-doped NETs. The resulting nanosize constructs were characterized for their diameters, zeta-potentials, absorption, and fluorescence emission spectra. We used fluorescence microscopic imaging to evaluate the capability of the constructs in imaging SKOV3 ovarian cancer cells. Based on dynamic light-scattering measurements, ICG- and IbA-doped NETs had similar diameter distributions (Z-average diameter of 236 and 238 nm, respectively) in phosphate-buffered saline supplemented with 10% fetal bovine serum, which remained nearly constant over the course of 2 h at 37 °C. Despite a much-lower loading efficiency of IbA (∼0.7-8%) as compared to ICG (10-45%), the integrated normalized fluorescence emission of IbA-NETs was 2- to 6-fold higher than ICG-doped NETs. IbA-NETs also demonstrated an enhanced capability in fluorescence imaging of SKOV3 ovarian cancer cells, and can serve as potentially effective nanoprobes for the fluorescence imaging of cancerous cells.