Immunoelectron Microscopic Analysis Research Articles

Diagnostic and Therapeutic Aspects of Monoclonal Gammopathies of Renal Significance (MGRS): An Update.

Monoclonal gammopathy of renal significance (MGRS) refers to a group of renal disorders caused by a monoclonal immunoglobulin (MIg), secreted by a non-malignant B-cell clone. Unlike overt multiple myeloma or B-cell proliferation, MGRS does not meet those diagnostic criteria. However, it is associated with significant morbidity, due to severe renal, and sometimes systemic, lesions induced by the MIg. Early recognition is crucial, as chemotherapy to suppress MIg secretion often improves outcomes. The spectrum of renal diseases in MGRS is broad, including both well-known conditions like AL amyloidosis and newly described lesions. Kidney biopsy is essential to determine the specific lesion associated with MGRS and assess its severity. Diagnosis involves integrating morphologic alterations using techniques such as light microscopy, immunofluorescence (IF), electron microscopy, and, in some cases, IF staining for Ig isotypes, immunoelectron microscopy, and proteomic analysis. Additionally, a complete hematologic evaluation, including serum and urine protein electrophoresis, immunofixation, and a serum-free light-chain assay, is necessary.

NcPTP2, a polar tube protein, interacts with spore wall protein in the parasitic microsporidian Nosema ceranae.

Microsporidia is an obligate intracellular eukaryote, which is capable of parasitizing vertebrates and invertebrates. Nosema ceranae, which can infect both Apis mellifera and Apis cerana, poses a serious threat and causes heavy losses to the worldwide apiculture. During infection, polar tube, a highly specialized invasion structure, ejected from the spore to deliver the sporoplasm into host cells to cause infection. Although seven different polar tube proteins (PTP1 ~ 7) have been reported from various microsporidia and showed key functions associated with spore invasion and proliferation, no systematic analysis on identification and characterization of polar tube proteins from N. ceranae was found. The polar tube proteins 2 (NcPTP2) was identified from the total polar tube proteins of N. ceranae by LC_MS/MS and the transcriptional profile was performed by RT-PCR. Sequence characterization analysis revealed that NcPTP2 was rich in lysine and had a signal peptide at the N-terminal. It had 3 potential O-glycosylation sites and 6 potential N-glycosylation sites. 25 phosphorylation sites were found on serine, tyrosine and threonine sites. Sequence alignment analysis revealed that NcPTP2 was homologous and had conserved cysteine residues with PTP2 proteins from other microsporidia. Indirect immunofuorescence analysis (IFA) and Immunoelectron Microscopy analysis (IEM) confirmed that NcPTP2 was localized on the polar tube of the germinated spores. The interaction between NcPTP2 and spore wall protein in N. ceranae indicated its potential function in anchoring and coiling of polar tube in spore. NcPTP2 was the first subcellular localized polar tube protein in N. ceranae and this work could provide an important basis for further analyzing the biological functions of polar tube proteins and uncovering the infection mechanism of N. ceranae to the host cells.

Investigating the cell membrane localization of PADI4 in breast cancer cells and inhibition of anti-PADI4 monoclonal antibody

BackgroundPeptidyl arginine deiminase 4 (PADI4) is a post-translational modification enzymecan that converts arginine in protein into citrulline in the presence of calcium ions, which is called citrullination. PADI4 has been reported to be expressed in the cytoplasm and nucleus in a variety of malignant tumors. Based on the GeneCards database and our previous research, it is speculated that PADI4 may also be expressed on the cell membrane. This study aimed to confirm the membrane expression of PADI4 and the effect of anti-PADI4 antibodies on cell membrane PADI4. This may be another mechanism of action of anti-PADI4 monoclonal antibodies in the treatment of breast cancer.MethodsThe subcellular localizations of PADI4 in MDA-MB-231 and MCF-7 breast cancer cells were determined by immunofluorescence, immunoelectron microscopy, and Western blot analysis. The tumor cells were treated with PADI4 antibody, and cell proliferation, migration, colony formation, apoptosis, glycolysis, and epithelial-mesenchymal transition (EMT) were measured as well as the expression of some essential tumor genes.ResultsPADI4 was not only localized in the nucleus and cytoplasm of breast cancer cells but was also detected on the cell membrane. Following PADI4 antibody treatment, cell proliferation, migration, colony formation, EMT, and ATP production through glycolysis were decreased, and the mRNA expression of MYC proto-oncogene (MYC), FAT atypical cadherin 1 (FAT1), nuclear factor kappa B subunit 1 (NFκB), and tumor necrosis factor (TNF-α) in breast cancer cells was downregulated, while the mRNA expression of tumor protein p63 (TP63) was upregulated.ConclusionsPADI4 is expressed on the cell membrane in breast cancer cells. Anti-PADI4 antibodies can affect the biological functions of cell membrane PADI4, including proliferation, migration, apoptosis, and glycolysis, thereby inhibiting tumor progression.Graphical abstract

Semaphorin3A Exacerbates Cardiac Microvascular Rarefaction in Pressure Overload-Induced Heart Disease.

Microvascular endothelial cells (MiVECs) impair angiogenic potential, leading to microvascular rarefaction, which is a characteristic feature of chronic pressure overload-induced cardiac dysfunction. Semaphorin3A (Sema3A) is a secreted protein upregulated in MiVECs following angiotensin II (Ang II) activation and pressure overload stimuli. However, its role and mechanism in microvascular rarefaction remain elusive. The function and mechanism of action of Sema3A in pressure overload-induced microvascular rarefaction, is explored, through an Ang II-induced animal model of pressure overload. RNA sequencing, immunoblotting analysis, enzyme-linked immunosorbent assay, quantitative reverse transcription polymerase chain reaction (qRT-PCR), and immunofluorescence staining results indicate that Sema3A is predominantly expressed and significantly upregulated in MiVECs under pressure overload. Immunoelectron microscopy and nano-flow cytometry analyses indicate small extracellular vesicles (sEVs), with surface-attached Sema3A, to be a novel tool for efficient release and delivery of Sema3A from the MiVECs to extracellular microenvironment. To investigate pressure overload-mediated cardiac microvascular rarefaction and cardiac fibrosis in vivo, endothelial-specific Sema3A knockdown mice are established. Mechanistically, serum response factor (transcription factor) promotes the production of Sema3A; Sema3A-positive sEVs compete with vascular endothelial growth factor A to bind to neuropilin-1. Therefore, MiVECs lose their ability to respond to angiogenesis. In conclusion, Sema3A is a key pathogenic mediator that impairs the angiogenic potential of MiVECs, which leads to cardiac microvascular rarefaction in pressure overload-induced heart disease.

Proteomic analysis of extracellular vesicles from tick hemolymph and uptake of extracellular vesicles by salivary glands and ovary cells

BackgroundExtracellular vesicles (EVs) are a heterogeneous group of cell-derived membranous structures that are important mediators of intercellular communication. Arthropods transport nutrients, signaling molecules, waste and immune factors to all areas of the body via the hemolymph. Little is known about tick hemolymph EVs.MethodsHemolymph was collected from partially fed Rhipicephalus haemaphysaloides and Hyalomma asiaticum ticks by making an incision with a sterile scalpel in the middle (between the femur and metatarsus) of the first pair of legs, which is known as leg amputation. EVs were isolated from hemolymph by differential centrifugation and characterized by transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Proteins extracted from the hemolymph EVs were analyzed by 4D label-free proteomics. The EVs were also examined by western blot and immuno-electron microscopy analysis. Intracellular incorporation of PHK26-labeled EVs was tested by adding labeled EVs to tick salivary glands and ovaries, followed by fluorescence microscopy.ResultsIn this study, 149 and 273 proteins were identified by 4D label-free proteomics in R. haemaphysaloides and H. asiaticum hemolymph EVs, respectively. TEM and NTA revealed that the sizes of the hemolymph EVs from R. haemaphysaloides and H. asiaticum were 133 and 138 nm, respectively. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analyses of identified proteins revealed pathways related to binding, catalytic and transporter activity, translation, transport and catabolism, signal transduction and cellular community. The key EV marker proteins RhCD9, RhTSG101, Rh14-3-3 and RhGAPDH were identified using proteomics and western blot. The presence of RhFerritin-2 in tick hemolymph EVs was confirmed by western blot and immuno-electron microscopy. We demonstrated that PKH26-labeled hemolymph EVs are internalized by tick salivary glands and ovary cells in vitro.ConclusionsThe results suggest that tick EVs are secreted into, and circulated by, the hemolymph. EVs may play roles in the regulation of tick development, metabolism and reproduction.Graphical

Diagnostic Challenges and Solutions in Systemic Amyloidosis

Amyloidosis refers to a clinically heterogeneous group of disorders characterized by the extracellular deposition of amyloid proteins in various tissues of the body. To date, 42 different amyloid proteins that originate from normal precursor proteins and are associated with distinct clinical forms of amyloidosis have been described. Identification of the amyloid type is essential in clinical practice, since prognosis and treatment regimens both vary according to the particular amyloid disease. However, typing of amyloid protein is often challenging, especially in the two most common forms of amyloidosis, i.e., the immunoglobulin light chain amyloidosis and transthyretin amyloidosis. Diagnostic methodology is based on tissue examinations as well as on noninvasive techniques including serological and imaging studies. Tissue examinations vary depending on the tissue preparation mode, i.e., whether it is fresh-frozen or fixed, and they can be carried out by ample methodologies including immunohistochemistry, immunofluorescence, immunoelectron microscopy, Western blotting, and proteomic analysis. In this review, we summarize current methodological approaches used for the diagnosis of amyloidosis and discusses their utility, advantages, and limitations. Special attention is paid to the simplicity of the procedures and their availability in clinical diagnostic laboratories. Finally, we describe new methods recently developed by our team to overcome limitations existing in the standard assays used in common practice.

Immunoelectron Microscopic Analysis of Dipeptidyl-Peptidases and Dipeptide Transporter Involved in Nutrient Acquisition in Porphyromonas gingivalis.

Porphyromonas gingivalis is an asaccharolytic, Gram-negative, anaerobic bacterium representing a keystone pathogen in chronic periodontitis. The bacterium's energy production depends on the metabolism of amino acids, which are predominantly incorporated as dipeptides via the proton-dependent oligopeptide transporter (Pot). In this study, the localization of dipeptidyl-peptidases (DPPs) and Pot was investigated for the first time in P. gingivalis using immunoelectron microscopy with specific antibodies for the bacterial molecules and gold-conjugated secondary antibodies on ultrathin sections. High-temperature protein G and hemin-binding protein 35 were used as controls, and the cytoplasmic localization of the former and outer membrane localization of the latter were confirmed. P. gingivalis DPP4, DPP5, DPP7, and DPP11, which are considered sufficient for complete dipeptide production, were detected in the periplasmic space. In contrast, DPP3 was localized in the cytoplasmic space in accord with the absence of a signal sequence. The inner membrane localization of Pot was confirmed. Thus, spatial integration of the nutrient acquisition system exists in P. gingivalis, in which where dipeptides are produced in the periplasmic space by DPPs and readily transported across the inner membrane via Pot.

Chloroplast Envelopes Play a Role in the Formation of Autophagy-Related Structures in Plants.

Autophagy is a degradation process of cytoplasmic components that is conserved in eukaryotes. One of the hallmark features of autophagy is the formation of double-membrane structures known as autophagosomes, which enclose cytoplasmic content destined for degradation. Although the membrane source for the formation of autophagosomes remains to be determined, recent studies indicate the involvement of various organelles in autophagosome biogenesis. In this study, we examined the autophagy process in Bienertia sinuspersici: one of four terrestrial plants capable of performing C4 photosynthesis in a single cell (single-cell C4 species). We demonstrated that narrow tubules (stromule-like structures) 30-50 nm in diameter appear to extend from chloroplasts to form the membrane-bound structures (autophagosomes or autophagy-related structures) in chlorenchyma cells of B. sinuspersici during senescence and under oxidative stress. Immunoelectron microscopic analysis revealed the localization of stromal proteins to the stromule-like structures, sequestering portions of the cytoplasm in chlorenchyma cells of oxidative stress-treated leaves of B. sinuspersici and Arabidopsis thaliana. Moreover, the fluorescent marker for autophagosomes GFP-ATG8, colocalized with the autophagic vacuole maker neutral red in punctate structures in close proximity to the chloroplasts of cells under oxidative stress conditions. Together our results implicate a role for chloroplast envelopes in the autophagy process induced during senescence or under certain stress conditions in plants.

Biological properties of Staphylococcus virus ΦSA012 for phage therapy

Staphylococcus virus ΦSA012 has a wide host range and efficient lytic activity. Here, we assessed the biological stability of ΦSA012 against temperature, freeze-thawing, and pH to clinically apply the phage. In addition, inoculation of ΦSA012 through i.p. and i.v. injections into mice revealed that phages were reached the limit of detection in serum and accumulated notably spleens without inflammation at 48h post-inoculation. Furthermore, inoculation of ΦSA012 through s.c. injections in mice significantly induced IgG, which possesses neutralizing activity against ΦSA012 and other Staphylococcus viruses, ΦSA039 and ΦMR003, but not Pseudomonas viruses ΦS12-3 and ΦR18 or Escherichia viruses T1, T4, and T7 in vitro. Immunoelectron microscopic analysis showed that purified anti-phage IgG recognizes the long-tail fiber of staphylococcus viruses. Although S. aureus inoculation resulted in a 25% survival rate in a mouse i.p. model, ΦSA012 inoculation (i.p.) improved the survival rate to 75%; however, the survival rate of ΦSA012-immunized mice decreased to less than non-immunized mice with phage i.v. injection at a MOI of 100. These results indicated that ΦSA012 possesses promise for use against staphylococcal infections but we should carefully address the appropriate dose and periods of phage administration. Our findings facilitate understandings of staphylococcus viruses for phage therapy.

Distribution and Localization of Mahogunin Ring Finger 1 in the Mouse Central Nervous System.

Mahogunin ring finger 1 (MGRN1), an E3 ubiquitin, is involved in several physiological and neuropathological processes. Although mgrn1 mRNA is widely distributed in the central nervous system (CNS), detailed information on its cellular and subcellular localization is lacking and its physiological role remains unclear. In this study, we aimed to determine the distribution of MGRN1 in the mouse CNS using a newly produced antibody against MGRN1. We found that the MGRN1 protein was expressed in most neuronal cell bodies. An intense MGRN1 expression was also observed in the neuropil of the gray matter in different regions of the CNS, including the main olfactory bulb, cerebral cortex, caudate, putamen, thalamic nuclei, hypothalamic nuclei, medial eminence, superior colliculus, hippocampus, dentate gyrus, and spinal cord. Contrastingly, no MGRN1 expression was observed in glial cells. Double fluorescence and immunoelectron microscopic analyses revealed the intracellular distribution of MGRN1 in pre-synapses and near the outer membrane of the mitochondria in neurons. These findings indicate that MGRN1 is more widely expressed throughout the CNS; additionally, the intracellular expression of MGRN1 suggests that it may play an important role in synaptic and mitochondrial functions.

Abstract P3040: Mitochondrial Membrane Protein Sigmar1 Regulates Mitochondrial Ultrastructure And Respiratory Functions In The Heart

Background: Sigma-1 receptor (Sigmar1) is multifunctional, ubiquitously expressed chaperone protein in mammalian cell systems. Earlier biochemical and immuno-electron microscopic analysis revealed Sigmar1’s cellular localization depends on cell and tissue systems, explaining its involvement in regulating diverse cellular and molecular functions. However, Sigmar1’s localization at organelle levels, membrane tropism, and direct molecular functions in cardiomyocytes remain elusive. Objective: We conducted systematic biochemical, microscopic, and functional assays to define Sigmar1’s subcellular localization, membrane topology, and functions in the heart. Methods and Results: Immuno-labeled quantum dots (QDs) in transmission electron microscopy revealed anti-Sigmar1 labeled QDs on the mitochondrial membranes, lysosomes, and at the sarcoplasmic reticulum-mitochondria interface. Subcellular fractionation of heart lysates also confirmed Sigmar1’s distribution in purified mitochondrial and lysosomal fractions. We further confirmed Sigmar1’s mitochondrial localization by Sigmar1’s colocalization with Mito-Tracker Red labeled isolated cardiac mitochondria. Biochemical experiments constituting alkaline extraction, detergent solubilization, and dose-dependent Proteinase K digestion on isolated heart mitochondria demonstrated Sigmar1 as an integral mitochondrial membrane protein. Sigmar1’s structural requirement for mitochondrial localization by expressing Flag-tagged Sigmar1 fragments demonstrated N-terminal required for mitochondrial localization. High-resolution mitochondrial respirometry studies showed that genetic loss of Sigmar1 in primary cardiomyocytes reduces mitochondrial respiration. Sigmar1 knock-out mice hearts also showed the accumulation of abnormal, irregular-shaped giant mitochondria and defects in mitochondrial respiration. Conclusions: Overall, our studies demonstrated that Sigmar1 is an integral mitochondrial membrane protein and is essential in maintaining mitochondrial ultrastructure and respiratory functions in the heart.

Activation of Extrasynaptic Kainate Receptors Drives Hilar Mossy Cell Activity.

Mossy cells (MCs) of the dentate gyrus are key components of an excitatory associative circuit established by reciprocal connections with dentate granule cells (GCs). MCs are implicated in place field encoding, pattern separation, and novelty detection, as well as in brain disorders such as temporal lobe epilepsy and depression. Despite their functional relevance, little is known about the determinants that control MC activity. Here, we examined whether MCs express functional kainate receptors (KARs), a subtype of glutamate receptors involved in neuronal development, synaptic transmission, and epilepsy. Using mouse hippocampal slices, we found that bath application of submicromolar and micromolar concentrations of the KAR agonist kainic acid induced inward currents and robust MC firing. These effects were abolished in GluK2 KO mice, indicating the presence of functional GluK2-containing KARs in MCs. In contrast to CA3 pyramidal cells, which are structurally and functionally similar to MCs and express synaptic KARs at mossy fiber (MF) inputs (i.e., GC axons), we found no evidence for KAR-mediated transmission at MF-MC synapses, indicating that most KARs at MCs are extrasynaptic. Immunofluorescence and immunoelectron microscopy analyses confirmed the extrasynaptic localization of GluK2-containing KARs in MCs. Finally, blocking glutamate transporters, a manipulation that increases extracellular levels of endogenous glutamate, was sufficient to induce KAR-mediated inward currents in MCs, suggesting that MC-KARs can be activated by increases in ambient glutamate. Our findings provide the first direct evidence of functional extrasynaptic KARs at a critical excitatory neuron of the hippocampus.SIGNIFICANCE STATEMENT Hilar mossy cells (MCs) are an understudied population of hippocampal neurons that form an excitatory loop with dentate granule cells. MCs have been implicated in pattern separation, spatial navigation, and epilepsy. Despite their importance in hippocampal function and disease, little is known about how MC activity is recruited. Here, we show for the first time that MCs express extrasynaptic kainate receptors (KARs), a subtype of glutamate receptors critically involved in neuronal function and epilepsy. While we found no evidence for synaptic KARs in MCs, KAR activation induced strong action potential firing of MCs, raising the possibility that extracellular KARs regulate MC excitability in vivo and may also promote dentate gyrus hyperexcitability and epileptogenesis.

The diffuse distribution of Nav1.2 on mid-axonal regions is a marker for unmyelinated fibers in the central nervous system

Unmyelinated fibers in the central nervous system are known to exist in hippocampal mossy fibers, cerebellar parallel fibers and striatal projection fibers. Previously, we and others reported diffuse distribution of Nav1.2, a voltage-gated sodium channel α-subunit encoded by the SCN2A gene, on unmyelinated striatal projection fibers. Mutations in the SCN2A gene are associated with epilepsies and autism. In this study, we investigated the distribution of Nav1.2 on the unmyelinated fibers in the corpus callosum and stria terminalis by immunohistochemistry and immunoelectron microscopy analysis, suggesting that diffuse localization of Nav1.2 on mid-axonal regions can be a useful marker for unmyelinated fibers.

The two faces of mast cells in vitiligo pathogenesis

Aim: Previously, we reported increased number of T helper 17 (Th17) cells in vitiligo. However, in our recent study, tryptase and interleukin (IL)17 double positive cells which identified by polyclonal anti-IL17 antibody with specificity for IL17A, B, D, F was observed, but these mast cells cannot be stained by monoclonal anti-IL17 antibody with specificity for IL17A. Therefore, this study was aimed to clarify the role of mast cells in induction and progression of vitiligo. Methods: Mast cells were stained with two antibodies against IL17 and one antibody against tryptase by immunofluorescent staining. Furthermore, immunoelectron microscopy (IEM) analyses were conducted using anti-tryptase. In vitro, cultured epidermal keratinocytes were treated with agents which released by mast cells. Expression levels of mRNA were analyzed by real-time polymerase chain reaction (PCR), expression of protein levels was analyzed by western blotting. Results: An increased number of tryptase positive mast cells was observed at the lesional skin of upper dermis in vitiligo and rhododendrol-induced leukoderma (RDIL). These mast cells showed prominent degranulation in vitiligo. Interestingly, the melanosome forming glycoprotein non-metastatic melanoma protein B (GPNMB) is downregulated in the lesional basal keratinocytes in vitiligo and mast cell tryptase contributes to this phenomenon. In addition, small interfering GPNMB RNA (siGPNMB RNA)-introduced keratinocytes increased melanocyte survival through stem cell factor (SCF) production in the melanocyte/keratinocyte co-culture system. Conclusions: Mast cells might be two-faced in vitiligo induction, progression, and recovery through the differential function of histamine and tryptase.

AML-108: Exogenous Mitochondrial Transfer and Endogenous Mitochondrial Fission Facilitate Resistance to OxPhos Inhibition in AML

<h3>Context:</h3> Oxidative phosphorylation (OxPhos) inhibition induces mitochondrial trafficking from BM stromal cells to AML and is accompanied by mitochondrial fission and mitophagy. The mitochondrial coupling and crosstalk with BM stromal cells facilitate the development of resistance to OxPhos inhibition in AML cells. <h3>Objective:</h3> Acute myeloid leukemia (AML) cells are highly dependent on OxPhos for survival and continually adapt to fluctuations in nutrient and oxygen availability in the environment. We investigated how the BM microenvironment affects the response to OxPhos inhibition in AML by using a novel complex I OxPhos inhibitor, IACS-010759. <h3>Design:</h3> Primary AML cells from 26 patients, primary normal MSCs, and AML cell lines were utilized and treated with the OxPhos inhibitor IACS-0107598 and/or cytarabine. Cap analysis of gene expression transcriptome analyses for AML PDXs, primary samples, and AML cell lines has been performed. We performed an extracellular flux assay to measure the oxygen consumption rate. To visualize mitochondria, AML cell lines and MSCs were stably transfected with mitochondria-targeted PDHA1-GFP and -dsRed, respectively. Electron microscopy and immunoelectron microscopy analysis have been performed. <h3>Results:</h3> Cellular adhesion, growth, and apoptosis assays, along with measurements of mtDNA expression and mitochondrial reactive oxygen species generation, indicated that direct interactions with BM stromal cells triggered the compensatory activation of mitochondrial respiration and resistance to OxPhos inhibition in AML cells. Mechanistically, OxPhos inhibition induced (1) transfer of mesenchymal stem cell (MSC)-derived mitochondria to AML cells via tunneling nanotubes under direct-contact co-culture conditions and (2) mitochondrial fission with an increase in functional mitochondria and mitophagy in AML cells. Mitochondrial fission is known to enhance cell migration, and we observed mitochondrial transport to the leading edge of protrusions of migrating AML cells toward MSCs by electron microscopy analysis. We further demonstrated that cytarabine, a commonly used antileukemia agent, increased IACS-010759-triggered mitochondrial transfer from MSCs to AML cells. <h3>Conclusions:</h3> Our findings indicate an important role of exogenous mitochondrial trafficking from BM stromal cells to AML cells and of endogenous mitochondrial fission and mitophagy in the compensatory adaptation of leukemia cells to energetic stress in the BM microenvironment.

Trastuzumab Modulates the Protein Cargo of Extracellular Vesicles Released by ERBB2+ Breast Cancer Cells

Cancers overexpressing the ERBB2 oncogene are aggressive and associated with a poor prognosis. Trastuzumab is an ERBB2 specific recombinant antibody employed for the treatment of these diseases since it blocks ERBB2 signaling causing growth arrest and survival inhibition. While the effects of Trastuzumab on ERBB2 cancer cells are well known, those on the extracellular vesicles (EVs) released from these cells are scarce. This study focused on ERBB2+ breast cancer cells and aimed to establish what type of EVs they release and whether Trastuzumab affects their morphology and molecular composition. To these aims, we performed immunoelectron microscopy, immunoblot, and high-resolution mass spectrometry analyses on EVs purified by differential centrifugation of culture supernatant. Here, we show that EVs released from ERBB2+ breast cancer cells are polymorphic in size and appearance and that ERBB2 is preferentially associated with large (120 nm) EVs. Moreover, we report that Trastuzumab (Tz) induces the expression of a specific glycosylated 50 kDa isoform of the CD63 tetraspanin and modulates the expression of 51 EVs proteins, including TOP1. Because these proteins are functionally associated with organelle organization, cytokinesis, and response to lipids, we suggest that Tz may influence these cellular processes in target cells at distant sites via modified EVs.

Neutrophil specific granule and NETosis defects in gray platelet syndrome

Gray platelet syndrome (GPS) is an autosomal recessive bleeding disorder characterized by a lack of α-granules in platelets and progressive myelofibrosis. Rare loss-of-function variants in neurobeachin-like 2 (NBEAL2), a member of the family of beige and Chédiak-Higashi (BEACH) genes, are causal of GPS. It is suggested that BEACH domain containing proteins are involved in fusion, fission, and trafficking of vesicles and granules. Studies in knockout mice suggest that NBEAL2 may control the formation and retention of granules in neutrophils. We found that neutrophils obtained from the peripheral blood from 13 patients with GPS have a normal distribution of azurophilic granules but show a deficiency of specific granules (SGs), as confirmed by immunoelectron microscopy and mass spectrometry proteomics analyses. CD34+ hematopoietic stem cells (HSCs) from patients with GPS differentiated into mature neutrophils also lacked NBEAL2 expression but showed similar SG protein expression as control cells. This is indicative of normal granulopoiesis in GPS and identifies NBEAL2 as a potentially important regulator of granule release. Patient neutrophil functions, including production of reactive oxygen species, chemotaxis, and killing of bacteria and fungi, were intact. NETosis was absent in circulating GPS neutrophils. Lack of NETosis is suggested to be independent of NBEAL2 expression but associated with SG defects instead, as indicated by comparison with HSC-derived neutrophils. Since patients with GPS do not excessively suffer from infections, the consequence of the reduced SG content and lack of NETosis for innate immunity remains to be explored.

Maturation of Complex Synaptic Connections of Layer 5 Cortical Axons in the Posterior Thalamic Nucleus Requires SNAP25.

Synapses are able to form in the absence of neuronal activity, but how is their subsequent maturation affected in the absence of regulated vesicular release? We explored this question using 3D electron microscopy and immunoelectron microscopy analyses in the large, complex synapses formed between cortical sensory efferent axons and dendrites in the posterior thalamic nucleus. Using a Synaptosome-associated protein 25 conditional knockout (Snap25 cKO), we found that during the first 2 postnatal weeks the axonal boutons emerge and increase in the size similar to the control animals. However, by P18, when an adult-like architecture should normally be established, axons were significantly smaller with 3D reconstructions, showing that each Snap25 cKO bouton only forms a single synapse with the connecting dendritic shaft. No excrescences from the dendrites were formed, and none of the normally large glomerular axon endings were seen. These results show that activity mediated through regulated vesicular release from the presynaptic terminal is not necessary for the formation of synapses, but it is required for the maturation of the specialized synaptic structures between layer 5 corticothalamic projections in the posterior thalamic nucleus.

Expression and Identification of a Novel Spore Wall Protein in Microsporidian Nosema bombycis.

Microsporidia are a group of obligate intracellular parasites causing significant disease in human beings and economically important animals. Though a few spore wall proteins (SWPs) have now been identified in these intriguing species, the information on SWPs remains too little to elucidate the spore wall formation mechanisms of microsporidia. It has been well described that numerous proteins with tandem repeats tend to be localized on the cell wall of fungi and parasites. Previously, by scanning the proteins with tandem repeats in microsporidian Nosema bombycis, we obtained 83 candidate SWPs based on whether those proteins possess a signal peptide and/or transmembrane domain. Here, we further characterized a candidate protein (EOB13250) with three tandem repeats in the N-terminal region and a transmembrane domain in C-terminus of N.bombycis. Sequence analysis showed that the tandem repeat domain of EOB13250 was species-specific for this parasite. RT-PCR indicated that the expression of the gene encoding this protein started on the fourth day postinfection. After cloned and expressed in Escherichia coli, a polyclone antibody against the recombinant EOB13250 protein was prepared. Western blotting demonstrated this protein exist in N. bombycis. Immunofluorescence analysis (IFA) and immunoelectron microscopy analysis (IEM) further provided evidence that EOB13250 was an endospore wall protein. These results together suggested that EOB13250 was a novel spore wall protein of N. bombycis. This study provides a further enrichment of the number of identified spore wall proteins in microsporidia and advances our understanding of the spore wall formation mechanism in these obligate unicellular parasites.

Degradation of Mutant Protein Aggregates within the Endoplasmic Reticulum of Vasopressin Neurons.

SummaryMisfolded or unfolded proteins in the ER are said to be degraded only after translocation or isolation from the ER. Here, we describe a mechanism by which mutant proteins are degraded within the ER. Aggregates of mutant arginine vasopressin (AVP) precursor were confined to ER-associated compartments (ERACs) connected to the ER in AVP neurons of a mouse model of familial neurohypophysial diabetes insipidus. The ERACs were enclosed by membranes, an ER chaperone and marker protein of phagophores and autophagosomes were expressed around the aggregates, and lysosomes fused with the ERACs. Moreover, lysosome-related molecules were present within the ERACs, and aggregate degradation within the ERACs was dependent on autophagic-lysosomal activity. Thus, we demonstrate that protein aggregates can be degraded by autophagic-lysosomal machinery within specialized compartments of the ER.