EGFR does not directly interact with cortical actin: A SRRF'n'TIRF study.

The epidermal growth factor receptor (EGFR) governs pivotal signaling pathways in cell proliferation and survival, with mutations implicated in numerous cancers. The organization of EGFR on the plasma membrane (PM) is influenced by the lipids and the cortical actin (CA) cytoskeleton. Despite the presence of a putative actin-binding domain (ABD) spanning 13 residues, a direct interaction between EGFR and CA has not been definitively established. While disrupting the cytoskeleton can impact EGFR behavior, suggesting a connection, the influence of the static actin cytoskeleton has been found to be indirect. Here, we investigate the potential interaction between EGFR and CA, as well as the extent to which CA regulates EGFR's distribution on the PM using SRRF'n'TIRF, a spatiotemporal super-resolution microscopy technique that provides sub-100 nm resolution and ms-scale dynamics from the same data set. To label CA, we constructed PMT-mEGFP-F-tractin, which combines an inner leaflet targeting domain PMT, fluorescent probe mEGFP, and the actin-binding protein F-tractin. In addition to EGFR-mEGFP, we included two control constructs: 1) an ABD deletion mutant, EGFRΔABD-mEGFP serving as a negative control and 2) EGFR-mApple-F-tractin, where F-tractin is fused to the C-terminus of EGFR-mApple, serving as the positive control. We find that EGFR-mEGFP and EGFRΔABD-mEGFP show similar membrane dynamics, implying that EGFR-mEGFP dynamics and organization are independent of CA. EGFR dynamics show CA dependence when F-tractin is anchored to the cytoplasmic tail. Together, our results demonstrate that EGFR does not directly interact with the CA in its resting and activated state.

The dependence of EGFR oligomerization on environment and structure: A camera-based N&B study.

Number and brightness (N&B) analysis is a fluorescence spectroscopy technique to quantify oligomerization of the mobile fraction of proteins. Accurate results, however, rely on a good knowledge of nonfluorescent states of the fluorescent labels, especially of fluorescent proteins, which are widely used in biology. Fluorescent proteins have been characterized for confocal, but not camera-based, N&B, which allows, in principle, faster measurements over larger areas. Here, we calibrate camera-based N&B implemented on a total internal reflection fluorescence microscope for various fluorescent proteins by determining their propensity to be fluorescent. We then apply camera-based N&B in live CHO-K1 cells to determine the oligomerization state of the epidermal growth factor receptor (EGFR), a transmembrane receptor tyrosine kinase that is a crucial regulator of cell proliferation and survival with implications in many cancers. EGFR oligomerization in resting cells and its regulation by the plasma membrane microenvironment are still under debate. Therefore, we investigate the effects of extrinsic factors, including membrane organization, cytoskeletal structure, and ligand stimulation, and intrinsic factors, including mutations in various EGFR domains, on the receptor's oligomerization. Our results demonstrate that EGFR oligomerization increases with removal of cholesterol or sphingolipids or the disruption of GM3-EGFR interactions, indicating raft association. However, oligomerization is not significantly influenced by the cytoskeleton. Mutations in either I706/V948 residues or E685/E687/E690 residues in the kinase and juxtamembrane domains, respectively, lead to a decrease in oligomerization, indicating their necessity for EGFR dimerization. Finally, EGFR phosphorylation is oligomerization dependent, involving the extracellular domain (550-580 residues). Coupled with biochemical investigations, camera-based N&B indicates that EGFR oligomerization and phosphorylation are the outcomes of several molecular interactions involving the lipid content and structure of the cell membrane and multiple residues in the kinase, juxtamembrane, and extracellular domains.

FCS videos: Fluorescence correlation spectroscopy in space and time.

Fluorescence Correlation Spectroscopy (FCS), invented more than 50 years ago is a widely used tool providing information on molecular processes in a variety of samples from materials to life sciences. In the last two decades FCS was multiplexed and ultimately made into an imaging technique that provided maps of molecular parameters over whole sample cross-section. However, it was still limited by a measurement time on the order of minutes. With the improvement of FCS time resolution to seconds using deep learning, we extend here FCS to so-called FCS videos that can provide information how the molecular parameters determined by Imaging FCS change in space and time. This opens up new possibilities for the investigation of molecular processes. Here, we demonstrate the feasibility of the approach and show FCS video applications to lipid bilayers and cell membranes.

SMO-CRISPR-mediated apoptosis in CD133-targeted cancer stem cells and tumor growth inhibition.

Cancer stem cells (CSCs) possess the ability to indefinitely proliferate and resist therapy, leading to cancer relapse and metastasis. To address this, we aimed to develop a CSC-inclusive therapy that targets both CSCs and non-CSC glioblastoma (GBM) cells. We accomplished this by using a smoothened (SMO) CRISPR/Cas9 plasmid to suppress the hedgehog pathway in CSCs, in combination with inhibiting the serine hydroxymethyl transferase 1 (SHMT1)-driven thymidylate biosynthesis pathway in non-CSC GBM cells using SHMT1 siRNA (siSHMT1). We targeted CSCs using a CD133 peptide attached to an osmotically active vitamin B6-coupled polydixylitol vector (VPX-CD133) by a photoactivatable heterobifunctional linker. VPX-CD133 nanocomplexes in comparison to VPX complexes remarkably targeted and transfected CSCs both in vitro and in subcutaneous tumor. The VPX-CD133-mediated targeted delivery of SMO CRISPR in CSCs led to SMO suppression that negatively affected its growth. Next, we performed comprehensive therapy in xenograft mice using VPX-CD133, which delivered SMO-CRISPR to CSCs, and VPX, which delivered siSHMT1 to non-CSC GBM cells. The combined treatment induced apoptosis in a large number of cells, reduced tumor volume by up to 81%, and improved the health of treated mice significantly. By eliminating CSCs together with the non-CSC GBM cells, the combined study paves the way for developing CSC-inclusive therapies for GBM.

Insight towards the effect of the multi basic cleavage site of SARS-CoV-2 spike protein on cellular proteases.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection presents an immense global health problem. Spike (S) protein of coronavirus is the primary determinant of its entry into the host as it consists of both receptor binding and fusion domain. Besides tissue tropism, and host range, coronavirus pathogenesis are primarily controlled by the interaction of S protein with the cell receptor. Moreover, the proteolytic activation of S protein by host cell proteases plays a decisive role. The host-cell proteases have shown to be involved in the proteolysis of S protein and cleaving it into two functional subunits, S1 and S2, during the maturation process. In the present study, the interaction of the S protein of SARS-CoV-2 with different host proteases like furin, cathepsin B, and plasmin has been analyzed using molecular docking and molecular dynamics (MD) simulation. Incorporation of the furin cleavage site (R-R-A-R) in the S protein of SARS-CoV-2 has been studied by mutating the individual amino acid. MD simulation results suggest the polytropic nature of the S protein. Our analysis indicated that a single amino acid substitution in the polybasic cleavage site of S protein perturb the binding of cellular proteases. This mutation study might help to generate an attenuated SARS-CoV-2. Besides, targeting host proteases by inhibitors may result in a practical approach to stop the cellular spread of SARS-CoV-2 and develop its antiviral.

Synthesis, characterization and application of chitosan-N-(4-hydroxyphenyl)-methacrylamide derivative as a drug and gene carrier.

The aim of this study was to develop a green method to fabricate a novel CS modified N-(4-hydroxyphenyl)- methacrylamide conjugate (CSNHMA) and to evaluate its biomedical potential. CSNHMA has been prepared by a simple method via aza Michael addition reaction between CS and N- (4-hydroxyphenyl)-methacrylamide (NHMA) in ethanol. Its structural and morphological properties were characterized by various analysis techniques. The obtained results confirmed that a highly porous network structure of CSNHMA was successfully synthesized via aza Michael addition reaction. Consequently, it was analyzed as a drug and gene carrier. CSNHMA/pGL3 showed an enhanced buffering capacity due to the presence of NHMA moiety leading to higher transfection efficiency in all cancer cells (A549, HeLa and HepG2) as compared to native CS and Lipofectamine®. Therefore, these findings clearly support the possibility of using CSNHMA as a good transfection agent. For in vitro drug release study, we prepared CSNHMA nanoparticles (NPs) and curcumin loaded CSNHMA NPs of size <230 nm respectively via the non-toxic ionic gelation route and the encapsulation efficiency of drug was found to be 77.03%. In vitro drug release studies demonstrated a faster and sustained release of curcumin loaded CSNHMA NPs at pH 5.0 compared to physiological pH.

SHMT1 siRNA-Loaded hyperosmotic nanochains for blood-brain/tumor barrier post-transmigration therapy.

The near-perivascular accumulation in solid tumors and short-lived span in circulation, derails even the most competent nanoparticles (NPs) from achieving their maximum therapeutic potential. Moreover, delivering them across the blood brain/tumor barrier (BBB/BTB) is further challenging to sought anticancer effect. To address these key challenges, we designed a linearly aligned nucleic acid-complexed polydixylitol-based polymeric nanochains (X-NCs), with inherent hyperosmotic properties enabling transmigration of the BBB/BTB and navigation through deeper regions of the brain tumor. The high aspect ratio adds shape-dependent functional aspects to parent particles by providing effective payload increment and nuclear factor of activated T cells-5 (NFAT5)-mediated cellular uptake. Therefore, serine hydroxymethyltransferase 1 (SHMT1) siRNA-loaded nanochains not only demonstrated to transmigrate the BTB, but also resulted in remarkably reducing the tumor size to 97% in the glioblastoma xenograft brain tumor mouse models. Our study illustrates how the hyperosmotic nanochains with high aspect ratio and aligned structure can accelerate a therapeutic effect in aggressive brain tumors post-transmigration of the BBB/BTB by utilizing an NFAT5 mode of uptake mechanism.

Reduced graphene oxide-incorporated calcium phosphate cements with pulsed electromagnetic fields for bone regeneration.

Natural calcium phosphate cements (CPCs) derived from sintered animal bone have been investigated to treat bone defects, but their low mechanical strength remains a critical limitation. Graphene improves the mechanical properties of scaffolds and promotes higher osteoinduction. To this end, reduced graphene oxide-incorporated natural calcium phosphate cements (RGO-CPCs) are fabricated for reinforcement of CPCs' characteristics. Pulsed electromagnetic fields (PEMFs) were additionally applied to RGO-CPCs to promote osteogenic differentiation ability. The fabricated RGO-CPCs show distinct surface properties and chemical properties according to the RGO concentration. The RGO-CPCs' mechanical properties are significantly increased compared to CPCs owing to chemical bonding between RGO and CPCs. In in vitro studies using a mouse osteoblast cell line and rat-derived adipose stem cells, RGO-CPCs are not severely toxic to either cell type. Cell migration study, western blotting, immunocytochemistry, and alizarin red staining assay reveal that osteoinductivity as well as osteoconductivity of RGO-CPCs was highly increased. In in vivo study, RGO-CPCs not only promoted bone ingrowth but also enhanced osteogenic differentiation of stem cells. Application of PEMFs enhanced the osteogenic differentiation of stem cells. RGO-CPCs with PEMFs can overcome the flaws of previously developed natural CPCs and are anticipated to open the gate to clinical application for bone repair and regeneration.

Development of novel gene carrier using modified nano hydroxyapatite derived from equine bone for osteogenic differentiation of dental pulp stem cells.

Hydroxyapatite (HA) is a representative substance that induces bone regeneration. Our research team extracted nanohydroxyapatite (EH) from natural resources, especially equine bones, and developed it as a molecular biological tool. Polyethylenimine (PEI) was used to coat the EH to develop a gene carrier. To verify that PEI is well coated in the EH, we first observed the morphology and dispersity of PEI-coated EH (pEH) by electron microscopy. The pEH particles were well distributed, while only the EH particles were not distributed and aggregated. Then, the existence of nitrogen elements of PEI on the surface of the pEH was confirmed by EDS, calcium concentration measurement and fourier transform infrared spectroscopy (FT-IR). Additionally, the pEH was confirmed to have a more positive charge than the 25 kD PEI by comparing the zeta potentials. As a result of pGL3 transfection, pEH was better able to transport genes to cells than 25 kD PEI. After verification as a gene carrier for pEH, we induced osteogenic differentiation of DPSCs by loading the BMP-2 gene in pEH (BMP-2/pEH) and delivering it to the cells. As a result, it was confirmed that osteogenic differentiation was promoted by showing that the expression of osteopontin (OPN), osteocalcin (OCN), and runt-related transcription factor 2 (RUNX2) was significantly increased in the group treated with BMP-2/pEH. In conclusion, we have not only developed a novel nonviral gene carrier that is better performing and less toxic than 25 kD PEI by modifying natural HA (the agricultural byproduct) but also proved that bone differentiation can be effectively promoted by delivering BMP-2 with pEH to stem cells.

Methyl methacrylate modified chitosan: Synthesis, characterization and application in drug and gene delivery.

A methyl methacrylate (MMA) modified chitosan (CS) conjugate (CSMMA) has been synthesized by a green method via Michael addition reaction between CS and MMA in ethanol. The synthesized conjugate was characterized by FT-IR, 1H NMR, X-ray diffraction spectrometry and SEM analysis. The results confirmed that CS was covalently linked to MMA yielding a highly porous framework. The uses of CSMMA were analyzed as a potential gene and drug delivery agent. CSMMA proved to be a reasonably good gene delivery agent based on transfection efficiency studies in mammalian cancer cell lines (A549, HeLa and HepG2). For drug delivery studies, nanoparticles of the CSMMA biopolymer were prepared by ionic gelation method with sodium tripolyphosphate (TPP). The prepared nanoparticles were characterized in terms of FE-SEM, DLS and zeta potential. In vitro drug release study of curcumin loaded CSMMA nanoparticles showed its maximal entrapment efficiency up to 68% and the drug release was more rapid at a pH (5.0) lower than physiological pH.

JNK2 silencing and caspase-9 activation by hyperosmotic polymer inhibits tumor progression.

c-Jun N-terminal kinase 2 (JNK2) is primarily responsible for the oncogenic transformation of the transcription factor c-Jun. Expression of the proto-oncogene c-Jun progresses the cell cycle from G1 to S phase, but when its expression becomes awry it leads to uncontrolled proliferation and angiogenesis. Delivering a JNK2 siRNA (siJNK2) in tumor tissue was anticipated to reverse the condition with subsequent onset of apoptosis which predominantly requires an efficient delivering system capable of penetrating through the compact tumor mass. In the present study, it was demonstrated that polymannitol-based vector (PMGT) with inherent hyperosmotic properties was able to penetrate through and deliver the siJNK2 in the subcutaneous tumor of xenograft mice. Hyperosmotic activity of polymannitol was shown to account for the enhanced therapeutic delivery both in vitro and in vivo because of the induction of cyclooxygenase-2 (COX-2) which stimulates caveolin-1 for caveolae-mediated endocytosis of the polyplexes. Further suppression of JNK2 and hence c-Jun expression led to the activation of caspase-9 to induce apoptosis and inhibition of tumor growth in xenograft mice model. The study exemplifies PMGT as an efficient vector for delivering therapeutic molecules in compact tumor tissue and suppression of JNK2 introduces a strategy to inhibit tumor progression.

Chitosan/PEI patch releasing EGF and the EGFR gene for the regeneration of the tympanic membrane after perforation.

Damage to the eardrum causes acute pain and can lead to chronic otitis media if it develops into chronic tympanic membrane (TM) perforations. Chronic TM perforations are usually treated with surgical methods such as tympanoplasty and myringoplasty. However, these surgeries are not only complicated and difficult but also cost a lot of money. Our research team developed chitosan patches (E-CPs) that release epidermal growth factor (EGF) as a patch therapy to replace surgical methods. However, there was a limitation in the healing ratio of the treatment compared to the surgical methods. In this study, we developed EGF and epidermal growth factor receptor (EGFR) gene-releasing polyethyleneimine (PEI)/chitosan patches (EErP-CPs) to increase the regeneration of TM perforations. The addition of PEI increased the adhesion and migration ability of TM cells on the patches. The simultaneous release of the EGF and the EGFR gene further enhanced TM cell proliferation, adhesion and migratory ability. It was confirmed that the EGF protein and EGFR gene were released for 30 days; however, EGF was released and increased TM cell viability almost immediately after treatment and EGFR took a minimum of 3 days before showing its effect on improved cell viability. It was also shown that EErP-CPs are more hydrophilic and have more positive charge than E-CP because of added amine groups from PEI. In conclusion, the developed EErP-CPs resulted in the improved healing of TM perforations and can potentially be applied to the regeneration of both chronic and acute tympanic membrane perforations.

Development of a bio-electrospray system for cell and non-viral gene delivery.

Bio-electrospray technology is a very attractive tool for preparing scaffolds and depositing desired solutions on various targets by electric force. In this study, we focused on the application of a bio-electrospray (BES) technique to spray cells on the target and to simultaneously deliver genetic constructs into the cells, called non-viral gene delivery-based bio-electrospray (NVG-BES). Using this method, we tried to harvest the electric charge produced during electrospray for the cellular internalization of cationic polymer/DNA nanoparticles as well as the delivery of living cells on the desired substrate. Furthermore, we optimized the voltage, culture medium and polymeric cationic charges for high transfection efficiency and cell viability during NVG-BES. As a result, the solutions used during the NVG-BES process played an important role in improving transfection efficiency. We determined that a voltage of 10 kV with PBS as the spraying solution showed high transfection efficiency, probably due to the facilitation of cationic polymer/DNA nanocomplexes in cellular internalization and their subsequent expression. In conclusion, NVG-BES, as a novel method, is expected to deliver genes to cells and simultaneously deliver transfected cells to any substrate or scaffold.

Correction: Development of a bio-electrospray system for cell and non-viral gene delivery.

[This corrects the article DOI: 10.1039/C7RA12477E.].

Enhanced chitosan-DNA interaction by 2-acrylamido-2-methylpropane coupling for an efficient transfection in cancer cells.

Gene therapy is the treatment of human disorders by the introduction of genetic material to specific target cells of a patient. Chitosan and its derivatives show excellent biological properties including biocompatibility, biodegradability and nonallergenicity. Primary amines of chitosan are responsible for its cationic nature and hence binding and protection of DNA for intracellular delivery. But the transfection efficiency of chitosan based gene transporters is severely hampered by its poor physical properties such as low water solubility and high viscosity. In this study, primary amines of low molecular weight (LMW) chitosan were coupled with 2-acrylamido-2-methylpropane sulphonic acid (AMP) making it water soluble for its application in gene delivery. AMP modified chitosan (CSAMP) showed an enhanced interaction with DNA and a higher buffering capacity due to AMP amines leading to a higher transfection efficiency in cancer cells (A549, HeLa and HepG2) compared to native chitosan and Lipofectamine®. In vivo studies in Balb/c through intravenous injection demonstrated a higher luciferase expression compared to LMW chitosan.

Nucleotide biosynthesis arrest by silencing SHMT1 function via vitamin B6-coupled vector and effects on tumor growth inhibition.

Serine hydroxymethyltransferase isoforms (SHMT1 & SHMT2α), which serve as scaffold protein for the formation of a multi-enzyme complex and generate one-carbon unit for the de novo thymidylate biosynthesis pathway during DNA synthesis, are vitamin B6 (VB6)-dependent enzyme. Cancer cells with high proliferation intensity need increased SHMT activation which enforces the facilitated-diffusion of VB6 for the continuous functioning of thymidylate synthase cycle. Therefore, SHMT knockdown presents an alternative approach to prevent DNA synthesis in cancer cells; however, its potential to inhibit cancer growth remains unknown so far. Here we demonstrated that VB6 coupled to poly(ester amine) (VBPEA) enforces a high level of VTC (VB6-transporting membrane carriers)-mediated endocytosis of the complexed SHMT1 siRNA (siSHMT1) to interrupt the thymidylate biosynthesis pathway of cancer cells. The detrimental effect of SHMT1 knockdown on the disintegration of multi-enzyme complex resulted in cell cycle arrest and a decrease in cell's genomic DNA content, leading to enhanced apoptotic events in cancer cells. A reduction in tumor size was observed with constant SHMT1 suppression in xenograft mice. This study illustrates how silencing the SHMT1 expression inhibits cancer growth and the increased VB6 channeling for sustenance of cancer cells promotes VB6-coupled vector to elicit enhanced delivery of siSHMT1.

Highly efficient gene transfection by a hyperosmotic polymannitol based gene tranporter through regulation of caveolae and COX-2 induced endocytosis.

The regulation of cellular uptake to cross the cell membrane is one of the key strategies of importance for efficient gene transfection of non-viral vectors. Hyperosmotic activity of polyplexes may facilitate crossing of the membrane barrier by elevating the osmolarity of the extracellular matrix. In this study, we demonstrated that a polymannitol based gene transporter (PMGT) utilizes the hyperosmoticity contributed by the polymannitol backbone leading to accelerated cellular uptake and enhanced gene transfection. Mannitol dimethacrylate (MDM) monomer was synthesized by esterification of mannitol and methacryloyl chloride. The prepared MDM was then cross-linked with low molecular weight (LMW) branched polyethyleneimine (bPEI) by Michael addition reaction to produce PMGT. PMGT provided polyplex stability in serum, low cytotoxicity, and degradability due to the ester linkages present in the polymannitol backbone. Elevated transfection activity and efficiency, both in vitro and in vivo, were achieved by modulating the mode of cellular uptake due to the effect of the hyperosmotic properties of PMGT. Cyclooxygenase-2 (COX-2) inhibition by SC58236 revealed the up-regulation of this osmoprotectant molecule against the hyperosmotic activity of polymannitol, inducing rapid endocytosis of PMGT in order to re-balance the hyperosmotic environment. Various inhibition studies of endocytosis showed caveolae-mediated endocytosis to be the main route of cellular internalization to account for the enhanced transgene expression.

Triphenylamine coupled chitosan with high buffering capacity and low viscosity for enhanced transfection in mammalian cells, in vitro and in vivo.

Chitosan and its derivatives show excellent biological properties, including biocompatibility, biodegradability and non-allergenicity. The primary amines of chitosan are responsible for its cationic nature, which confer its electrostatic binding with anionic DNA and protects from DNA degradation during intracellular delivery. However, its poor physical properties, such as low water solubility and high viscosity, severely hamper the transfection efficiency and in vivo applicability of chitosan based gene transporters. In this study, highly soluble triphenylamine coupled chitosan (TPAC) was synthesized by coupling triphenylamine (TPA) with primary amines of low molecular weight (LMW) chitosan, offering lower viscosity at biological pH and at the concentrations required for in vivo gene delivery. TPAC inherits a higher buffering capacity due to the tertiary amines of TPA leading to enhanced endosomal escape compared to native LMW chitosan. Intracellular fate and co-localization studies of TPAC showed decreased co-localization of polyplexes with lysosomes, demonstrating an increased availability of delivered plasmid DNA to the nucleus. Low viscosity and smaller pGL3/TPAC polyplex size enabled in vivo studies in Balb/c mice through intravenous injection. The in vitro transfection and in vivo biodistribution of the pGL3/TPAC nanoplexes showed higher luciferase expression compared to chitosan, polyethyleneimine (PEI 25K) and lipofectamine®. Physicochemical characterization, cell viability assays, and degradation studies demonstrated that TPAC meets the standards of a good transfection agent.

The efficiency of membrane transport of vitamin B6 coupled to poly(ester amine) gene transporter and transfection in cancer cells.

Vitamin B6 (VB6) plays an essential role as a coenzyme in various cellular metabolic functions, including DNA biosynthesis for cellular growth and proliferation. VB6 is taken up by cells through facilitated diffusion via VB6 transporting membrane carrier (VTC). In this study, we demonstrated that the VB6-coupled poly(ester amine) (VBPEA) gene transporter utilizes this uptake mechanism, leading to enhanced vector transport inside the rapidly proliferating cancer cells with relatively high affinity. Physicochemical characterization, cell viability assays, and transfection studies showed VBPEA to meet the standards of a good transfection agent. Competitive inhibition of VBPEA uptake by its structural analog 4'-deoxypyridoxine hydrochloride revealed the involvement of VB6 specific transporting membrane carrier in VBPEA internalization in tumor cells. VBPEA elicit higher transfection levels in lung cancer cells than in normal lung cells, indicating that cancer cells which have a high demand for VB6, have a higher affinity for VB6-coupled vector. VB6 coupling to the gene transporter is important to enforce a high level of VTC-mediated endocytosis compared to VB6 alone. This system illustrated how understanding of the VB6 membrane transporter specificity allowed for the design of a VB6-coupled gene transporter with accelerated transfection activity in cancer cells owing to an advanced mode of internalization.