Fragmentation Of Golgi Apparatus Research Articles

PECULIARITIES OF RESPIRATORY CELLULAR IMPLICATIONS IN STREPTOZOTOCIN-INDUCED DIABETES: A FOCUS ON TYPE I ALVEOLOCYTES

Introduction. The escalating global prevalence of diabetes mellitus has ignited concerns, given its multifaceted repercussions that extend beyond conventional metabolic considerations. Recent scientific inquiries have firmly established a profound association between diabetes mellitus and abnormalities within the respiratory system, unveiling a nuanced interplay that transcends mere glycemic control. This study delves into the intricate and far-reaching influence of diabetes on the respiratory system, recognizing it as a vulnerable target organ susceptible to systemic repercussions. Compelling epidemiological evidence underscores a heightened prevalence of respiratory complications among individuals grappling with diabetes. This observation prompts a meticulous exploration of the pathophysiological underpinnings of this intricate relationship, spanning from molecular intricacies to clinical manifestations.
 The aim was to deepen our understanding of the impact of diabetes mellitus on the respiratory system by investigating the pathological alterations in type I alveolocytes within an experimental model of diabetes mellitus.
 Methods. In this experimental model we used 88 male Wistar rats (170-210 g). The rats were divided into three groups: Group 1 (n=10) consisted of intact rats; Group 2 (n=40) served as the control group, and Group 3 (n=38) constituted the experimental group where diabetes was induced by intraperitoneal administration of streptozotocin (Sigma, USA) diluted in 0.1 M citrate buffer with pH 4.5 at a dosage of 60 mg/kg of body weight. The control group received an equivalent volume of 0.1 M citrate buffer solution with a pH of 4.5 via intraperitoneal injection. All procedures were performed under sodium thiopental anesthesia at a dose of 60 mg/kg of body weight. Tissue samples were collected at intervals of 14, 28, 42, and 70 days post streptozotocin injection.
 For electron microscopy analysis, fragments of lung tissue were immersed in a 2.5% glutaraldehyde solution for fixation, followed by fixation in a 1% osmium tetroxide solution. After dehydration, the specimens were embedded in Epon Araldite. Sections, obtained through a "Tesla VS-490" ultramicrotome, underwent examination using a "PEM-125K" electron microscope.
 Results. Throughout the experiment, discernible changes in type I alveolocytes were observed. At 14 days, nuclei exhibited rounding or oval shape with uniform chromatin distribution. Mitochondria displayed small size, and the Golgi apparatus (GA) and granulated endoplasmic reticulum (GER) showed no significant alterations. By 28 days, nuclei adopted an oval shape, chromatin localized peripherally, and mitochondria exhibited diverse morphologies. Increased micropinocytotic vesicles indicated heightened cellular activity. At 42 days, hyperhydration became pronounced, nuclei displayed lower electron density, and cellular components showed advanced changes. By 70 days, dystrophic-destructive changes included low electron density nuclei, disorganized mitochondria, and fragmented GA and GER.
 Conclusion. This comprehensive ultrastructural analysis unveils the progressive impact of diabetes on type I alveolocytes, elucidating unique facets of pulmonary alterations over time. This study contributes to a growing body of knowledge, shedding light on the dynamic nature of pulmonary changes in diabetes mellitus, ultimately urging further exploration for a holistic understanding of its implications on respiratory health.

Abstract 2404: Role of TPD52L2 in cell migration and triple negative breast cancer progression

Abstract The Golgi apparatus plays an important role in cell migration and the establishment of epithelial polarity. A dispersed (or fragmented) Golgi ribbon is often seen in stressed cells and in various pathologies, including neurodegeneration or cancer, but whether and how a fragmented Golgi apparatus affect cellular function is poorly defined. Previously our lab has performed and analyzed published RNAi screens to identify genes required to maintain the Golgi ribbon. These candidate genes were filtered for altered expression patterns in breast cancer patients and for their association with survival data. The selected genes reevaluated by RNAi in BT549 breast cancer cells to assess the effect on Golgi fragmentation. One of the most effective hits was TPD52L2, a poorly characterised gene that encodes a membrane-associated protein that is overexpressed in various types of cancer. The aim of this project is to investigate the role of TPD52L2 in cell migration and cell invasion in breast cancer in order to understand the role of Golgi fragmentation in tumorigenesis. In random cell migration assays in dense and sparse seeding conditions, TPD52L2 depleted cells showed an altered actin cytoskeleton and were found to migrate faster in dense seeding without any change in directional persistence. These findings suggest that TPD52L2 not only is required to maintain an intact Golgi structure but also plays an important role in cellular motility and potentially metastasis. Citation Format: Seyedamirabbas Parizadeh, Stephan Geley, Veronika Reiterer-Farhan, Hesso Farhan. Role of TPD52L2 in cell migration and triple negative breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2404.

Exogenous spermine alleviates myocardial injury induced by hyperglycemia by inhibiting golgi stress

To investigate whether Golgi stress (GAS) is involved in diabetic cardiomyopathy (DCM) and whether myocardial protection of exogenous spermine is associated with regulation of GAS. Sixty Wistar rats were randomly divided into normal control group (Control), diabetic group (T1D, STZ 60 mg/kg intraperitoneal injection) and spermine group (T1D+Sp, spermine 5 mg/(kg·d) intraperitoneal injection) for 12 weeks. H9C2 rat cardiomyocytes were randomly divided into control group (Control, 10% FBS-DMEM culture), high glucose group (HG, 10% FBS-DMEM+40 mmol/L glucose) and spermine group (HG+Sp, 10% FBS-DMEM+40 mmol/L glucose+5 μmol/L spermine). Rat serum creatine kinase isoenzyme (CK-MB) and cardiac troponin T (cTnT) were detected by ELISA; Golgi protein GOLPH3, GM130 and Cleaved Caspase3 protein expressions were analyzed using Western blot; immunofluorescence was used to detect GOLPH3 cell localization. In the animal model, compared with the normal group, myocardial ultrastructural damage was obvious,the blood glucose, the serum myocardial enzymes CK-MB and cTnT, the expressions of GOLPH3 and cleaved caspase3 were increased or up-regulated significantly,meanwhile, the body weight,the ejection fraction (EF) and the expression of GM130 were decreased or down-regulated markedly in the diabetic group. In the cell model, similar results were obtained. Immunofluorescence showed stress fragmentation of Golgi apparatus. Exogenous spermine treatment could significantly alleviate the above mentioned damages. Golgi stress occurs in diabetic cardiomyopathy (DCM), and myocardial protection of exogenous spermine is associated with a reduction in Golgi stress (GAS).

A Genetic Variant in GOLGB1 Affects Golgi Function and Stroke Risk in Patients with Sickle Cell Disease

Background: Five to ten percent of patients with sickle cell disease (SCD) have a high risk of suffering an ischemic stroke before they are 10 years of age. The clinical consequences of stroke are severe yet our current mechanistic understanding of the causes of stroke in SCD is limited. There is strong evidence that there is genomic contribution to the risk of stroke, other than just the SCD gene mutation. By whole exome sequencing, we have shown that a specific coding variant in the GOLGB1 gene, Y1212C, is significantly associated with decreased risk of stroke. GOLGB1 encodes a conserved Golgi membrane protein that is essential for maintaining Golgi structure and associated protein transport. To elucidate how the GOLGB1 Y1212C variant is protective against stroke risk in SCD, we performed morphological analysis of Golgi in cultured primary macrophages and whole proteome analyses of peripheral immune cells isolated from SCD patients.Methods: For primary macrophage preparations, we collected whole blood from non-SCD controls (n=11) and pediatric SCD patients (n=12). Monocytic CD14 positive cells were isolated and cultured for nine days with granulocyte monocyte stimulating colony factor, fixed and sequentially stained with antibodies against GOLGB1, TGN-46 and GM130. DAPI was used as a nuclear stain. High resolution images were acquired on Zeiss LSM 780 laser scanning confocal microscope with a 63X oil objective. Golgi morphological analysis was performed using a MATLAB script for cell segmentation, estimation of individual cell area, quantification of Golgi fragments per cell, and Golgi volume and organelle spread index. For the proteomic analysis, we isolated peripheral blood mononuclear cells from 7 patients with SCD. These cells were immediately flash-frozen and stored at -80oC until proteomic processing. We used a label-free protocol using dual-pH reverse phase fractionation and peptide sequencing of digested samples on a Thermo Scientific Orbitrap mass spectrometer. Protein abundances in each sample were estimated by using the intensity-based absolute quantification algorithm and total protein normalization was done with a fraction of total score (iFOT). Data were evaluated using GraphPad Prism and statistical analyses for differences between SCD and non-SCD samples or between samples with and without the GOLGB1 variant were performed with unpaired Student's t-test or Kruskal-Wallis test; analyses for multiple group comparisons were performed with the one-way ANOVA method. Statistical significance was set at P < 0.05.Results: In cultured primary macrophages, SCD individuals with the GOLGB1 Y1212C variant had altered Golgi morphologies compared to individuals with wild-type GOLGB1. Overall, macrophages derived from patients with SCD (n=12) were significantly larger (average cell size 11,728 vs. 7,598; p<0.001) yet had smaller Golgi (average Golgi volume 69.6µm vs. 75.4µm, p<0.01) and with more detected Golgi fragments (12.3 vs. 10.2 per cell, p<0.01) compared to non-SCD controls (n=11). For SCD patients with the GOLGB1 variant (n=5 heterozygote and 1 homozygote), their Golgi apparatus were more compact (average spread index 0.087 vs. 0.079; p<0.05) and had less Golgi fragments per cell (average 10.9 vs. 13.9; p<0.05) compared to SCD patients wild-type for GOLGB1 (n=6). From the proteomics analysis of peripheral blood immune cells, we identified 73 proteins that were differentially expressed (p<0.05) between SCD patients with (n=3) and without (n=4) the GOLGB1 variant. Of these proteins, 64 (90%) had lower levels in patients with the GOLGB1 Y1212C variant. Pathway analysis of the identified proteins showed that there strong clustering of proteins involved in platelet activation, regulation of actin cytoskeleton, and COPI-independent Golgi-to-ER retrograde trafficking (Table 1).Conclusions: Our study has shown that a coding variant in GOLGB1, identified as protective against risk of stroke in patients with SCD, has significant effects on Golgi function in SCD samples. We observed that having the GOLGB1 Y1212C variant resulted in more compact and less fragmented Golgi apparatus. Proteomic analysis showed that SCD patients with the GOLGB1 variant also had significantly lower levels of proteins involved in platelet activation and Golgi trafficking. Our findings suggest a novel role for the Golgi apparatus in controlling protein flux that modulates risk of stroke in SCD. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Peritoneal Dialysis Fluid-Induced Fragmentation of Golgi Apparatus as a Biocompatibility Marker.

In vitro biocompatibility assessments that consider physiologically appropriate conditions of cell exposure to peritoneal dialysis fluids (PDFs) are still awaited. In this study, we found that fragmentation of Golgi apparatus occurred in a pH-dependent manner within 30-min exposure to five distinct commercially available PDFs, which showed no marked difference in their effects on cell viability in the conventional MTT assay. Fluorescence microscopy analysis of labeling antibody against cis-Golgi protein GM130 indicated that the stacked cisternal structure was maintained in the perinuclear area of both M199 culture medium and a neutral-pH PDF groups. However, this specific structure became partially disassembled over time even in a neutral-pH PDF, and fragmentation was markedly enhanced in cells exposed to neutralized-pH PDFs in correspondence with their intracellular pH; moreover, in acidic PDFs, Golgi staining was diffuse and scattered in the entire cytoplasm and showed partial aggregation. The Golgi fragmentation markedly observed with the neutralized PDFs could be reversed by replacing either the media with a neutral-pH medium or a mixture of PDF and PD effluent (PDF) in a gradient manner mimicking clinical conditions. Furthermore, although weaker than pH effect, notable effects of other PDF-related factors were also observed after 30-min exposure to pH-adjusted PDFs. Lastly, the results of studies conducted using MAPK/SAPK inhibitors indicated that the mechanism underlying the Golgi fragmentation described here differs from that associated with the fragmentation that occurs at the G2/M checkpoint in the cell cycle. We conclude that Golgi fragmentation is suitable for rapid biocompatibility assessment of PDF not only because of its strong pH dependence but also because the fragmentation is recognizably affected by PDF constituents.

SOD1 Mutations Causing Familial Amyotrophic Lateral Sclerosis Induce Toxicity in Astrocytes: Evidence for Bystander Effects in a Continuum of Astrogliosis.

Astrocytes contribute to the death of motor neurons via non-cell autonomous mechanisms of injury in amyotrophic lateral sclerosis (ALS). Since mutations in the gene encoding Cu/Zn superoxide dismutase (SOD1) underlie the neuropathology of some forms of familial ALS, we explored how expression of mutant SOD1 protein A4V SOD1-EGFP affected the biology of secondary murine astrocytes. A4V SOD1-EGFP expressing astrocytes (72h after transfection) displayed decreased mitochondrial activity (~45%) and L-glutamate transport (~25%), relative to cells expressing wild-type SOD1-EGFP. A4V SOD1-EGFP altered F-actin and Hoechst staining, indicative of cytoskeletal and nuclear changes, and altered GM130 labelling suggesting fragmentation of Golgi apparatus. SOD1 inclusion formation shifted from discrete to "punctate" over 72h with A4V SOD1-EGFP more rapidly producing inclusions than G85R SOD1-EGFP, and forming more punctate aggregates. A4V, not wild-type SOD1-EGFP, exerted a substantial, time-dependent effect on GFAP expression, and ~60% of astrocytes became stellate and hypertrophic at 72h. Spreading toxicity was inferred since at 72h ~80% of bystander cells exhibited hypertrophy and stellation. This evidence favours mutant SOD1-containing astrocytes releasing destructive species that alter the biology of adjacent astrocytes. This panoply of mutant SOD1-induced destructive events favours recruitment of astrocytes to non-cell autonomous injury in ALS.

Aggressive Behavior in Silent Subtype III Pituitary Adenomas May Depend on Suppression of Local Immune Response: A Whole Transcriptome Analysis.

Silent subtype III pituitary adenomas (SS-3) are clinically nonfunctional adenomas that are more aggressive in terms of invasion and risk of recurrence than their conventional null cell counterparts. We previously showed that these tumors can be distinguished by immunohistochemistry based on the identification of a markedly enlarged and fragmented Golgi apparatus. To understand the molecular correlates of differential aggressiveness, we performed whole transcriptome sequencing (RNAseq) on 4 SS-3 and 4 conventional null cell adenomas. The genes that were highly upregulated in all the SS-3 adenomas included 2 secreted proteins involved in the suppression of T-lymphocyte activity, i.e., ARG2 (multiple testing adjusted padj = 1.5 × 10-3) and SEMA3A (padj = 3.3 × 10-3). Highly downregulated genes in all the SS-3 adenomas included HLA-B (padj = 3.3 × 10-6), suggesting reduced antigen presentation by the adenoma to cytotoxic T-cells. Quantitative RT-PCR of these genes performed on the adenoma samples supported the RNAseq results. We also found a relative decrease in the overall concentration of T-lymphocytes in the SS-3 tumors. These results suggest that SS-3 adenomas actively suppress the immune system and raise the possibility that they may be treatable with immune checkpoint inhibitors or nonspecific cancer immunotherapies.

Identification of Rab41/6d Effectors Provides an Explanation for the Differential Effects of Rab41/6d and Rab6a/a' on Golgi Organization.

Unexpectedly, members of the Rab VI subfamily exhibit considerable variation in their effects on Golgi organization and trafficking. By fluorescence microscopy, neither depletion nor overexpression of the GDP-locked form of Rab6a/a', the first trans Golgi-associated Rab protein discovered, affects Golgi ribbon organization while, on the other hand, both Rab41/6d depletion and overexpression of GDP-locked form cause Golgi fragmentation into a cluster of punctate elements, suggesting that Rab41/6d has an active role in maintenance of Golgi ribbon organization. To establish a molecular basis for these differences, we screened for Rab41/6d interacting proteins by yeast two-hybrid assay. 155 non-repetitive hits were isolated and sequenced, and after searching in NCBI database, 102 different proteins and protein fragments were identified. None of these hits overlapped with any published Rab6a/a' effector. Eight putative Rab41 interactors involved in membrane trafficking were found. Significantly, these exhibited a preferential interaction with GTP- vs. GDP-locked Rab41/6d. Of the 8 hits, the dynactin 6, syntaxin 8, and Kif18A plasmids were the only ones expressing the full-length protein. Hence, these 3 proteins were selected for further study. We found that depletion of dynactin 6 or syntaxin 8, but not Kif18A, resulted in a fragmented Golgi apparatus that displayed a Rab41/6d knockdown phenotype, i.e., the Golgi apparatus was disrupted into a cluster of punctate Golgi elements. Co-immunoprecipation experiments verified that the interaction of dynactin 6 and syntaxin 8 with GTP-locked Rab41/6d was stronger than that with wild type Rab41/6d and least with the GDP-locked form. In contrast, co-immunoprecipitation interaction with Rab6a was greatest with the GDP-locked Rab6a, suggestive of a non-physiological interaction. In conclusion, we suggest that dynactin 6, a subunit of dynactin complex, the minus-end-directed, dynein motor, provides a sufficient molecular basis to explain the active role of Rab41/6d in maintaining Golgi ribbon organization while syntaxin 8 contributes more indirectly to Golgi positioning.

Golgi fragmentation in amyotrophic lateral sclerosis, an overview of possible triggers and consequences.

Amyotrophic Lateral Sclerosis (ALS) is an invariably fatal neurodegenerative disorder, which specifically targets motor neurons in the brain, brain stem and spinal cord. Whilst the etiology of ALS remains unknown, fragmentation of the Golgi apparatus is detected in ALS patient motor neurons and in animal/cellular disease models. The Golgi is a highly dynamic organelle that acts as a dispatching station for the vesicular transport of secretory/transmembrane proteins. It also mediates autophagy and maintains endoplasmic reticulum (ER) and axonal homeostasis. Both the trigger for Golgi fragmentation and the functional consequences of a fragmented Golgi apparatus in ALS remain unclear. However, recent evidence has highlighted defects in vesicular trafficking as a pathogenic mechanism in ALS. This review summarizes the evidence describing Golgi fragmentation in ALS, with possible links to other disease processes including cellular trafficking, ER stress, defective autophagy, and axonal degeneration.

Mammillary Bodies in Alzheimer's Disease: A Golgi and Electron Microscope Study.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, characterized by irreversible memory decline, concerning no rarely spatial memory and orientation, alterations of the mood and personality, gradual loss of motor skills, and substantial loss of capacities obtained by previous long education. We attempted to describe the morphological findings of the mammillary bodies in early cases of AD. Samples were processed for electron microscopy and silver impregnation techniques. The nuclei of the mammillary bodies demonstrated a substantial decrease in the neuronal population and marked abbreviation of dendritic arbors. Decrease in spine density and morphological abnormalities of dendritic spines was also seen. Synaptic alterations were prominent. Alzheimer's pathology, such as deposits of amyloid-β peptide and neurofibrillary degeneration, was minimal. Electron microscopy revealed mitochondrial alterations and fragmentation of Golgi apparatus, associated frequently with synaptic pathology.

Coat protein I depletion-associated Golgi fragmentation in an Alzheimer's disease model

The onset and progression of Alzheimer's disease (AD) is closely associated with amyloid β (Aβ) peptide-induced cytotoxicity and abnormal protein transportation caused by breakdown of endoplasmic reticulum (ER)–Golgi apparatus trafficking network. Although the fragmentation of Golgi apparatus has been reported in AD human patients and various AD model animals, the molecular mechanisms causing the morpho-functional impairments of Golgi apparatus during AD progression remain poorly understood. Thus, we investigated the ultrastructure of Golgi apparatus and coat protein I (COPI) expression in β-amyloid precursor protein/presenilin-1 double transgenic mouse and Aβ-stimulated BV-2 cell as an AD model using cryo-immunogold electron microscopy. In the neurons of the hippocampus of transgenic mouse and BV-2 cell, the cisternae of Golgi stacks were fragmented in difference with that of wild type mouse and cells. In addition, we further showed the COPI depletion in Golgi apparatus, which demonstrated the impairment of molecular integrities of Golgi apparatus. Taken together, our results provide insights into the Golgi apparatus-involved morphopathology of AD and we suggest that the Golgi fragmentation is caused by the depletion of COPI affecting the intra-Golgi transport through stimulation and accumulation of Aβ during AD development.

Golgi fragmentation and sphingomyelin transport to Chlamydia trachomatis during penicillin-induced persistence do not depend on the cytosolic presence of the chlamydial protease CPAF.

Chlamydia grows inside a cytosolic vacuole (the inclusion) that is supplied with nutrients by the host through vesicular and non-vesicular transport. It is unclear in many respects how Chlamydia organizes this transport. One model posits that the Chlamydia-induced fragmentation of the Golgi-apparatus is required for normal transport processes to the inclusion and for chlamydial development, and the chlamydial protease CPAF has been controversially implicated in Golgi-fragmentation. We here use a model of penicillin-induced persistence of infection with Chlamydia trachomatis to test this link. Under penicillin-treatment the inclusion grew in size for the first 24 h but after that growth was severely reduced. Penicillin did not reduce the number of infected cells with fragmented Golgi-apparatus, and normal Golgi-fragmentation was found in a CPAF-deficient mutant. Surprisingly, sphingomyelin transport into the inclusion and into the bacteria, as measured by fluorescence accumulation upon addition of labelled ceramide, was not reduced during penicillin-treatment. Thus, both Golgi-fragmentation and transport of sphingomyelin to C. trachomatis still occurred in this model of persistence. The portion of cells in which CPAF was detected in the cytosol, either by immunofluorescence or by immune-electron microscopy, was drastically reduced in cells cultured in the presence of penicillin. These data argue against an essential role of cytosolic CPAF for Golgi-fragmentation or for sphingomyelin transport in chlamydial infection.

Human Liver Cell Trafficking Mutants: Characterization and Whole Exome Sequencing

The HuH7 liver cell mutant Trf1 is defective in membrane trafficking and is complemented by the casein kinase 2α subunit CK2α’’. Here we identify characteristic morphologies, trafficking and mutational changes in six additional HuH7 mutants Trf2-Trf7. Trf1 cells were previously shown to be severely defective in gap junction functions. Using a Lucifer yellow transfer assay, remarkable attenuation of gap junction communication was revealed in each of the mutants Trf2-Trf7. Electron microscopy and light microscopy of thiamine pyrophosphatase showed that several mutants exhibited fragmented Golgi apparatus cisternae compared to parental HuH7 cells. Intracellular trafficking was investigated using assays of transferrin endocytosis and recycling and VSV G secretion. Surface binding of transferrin was reduced in all six Trf2-Trf7 mutants, which generally correlated with the degree of reduced expression of the transferrin receptor at the cell surface. The mutants displayed the same transferrin influx rates as HuH7, and for efflux rate, only Trf6 differed, having a slower transferrin efflux rate than HuH7. The kinetics of VSV G transport along the exocytic pathway were altered in Trf2 and Trf5 mutants. Genetic changes unique to particular Trf mutants were identified by exome sequencing, and one was investigated in depth. The novel mutation Ile34Phe in the GTPase RAB22A was identified in Trf4. RNA interference knockdown of RAB22A or overexpression of RAB22AI34F in HuH7 cells caused phenotypic changes characteristic of the Trf4 mutant. In addition, the Ile34Phe mutation reduced both guanine nucleotide binding and hydrolysis activities of RAB22A. Thus, the RAB22A Ile34Phe mutation appears to contribute to the Trf4 mutant phenotype.

Subcellular Mechanisms in Pulmonary Arterial Hypertension: Combinatorial Modalities that Inhibit Anterograde Trafficking and Cause Bone Morphogenetic Protein Receptor Type 2 Mislocalization

Abstract The natural history of familial pulmonary arterial hypertension (PAH) typically involves mutations in and/or haploinsuffciency of BMPR2 (gene for bone morphogenetic protein receptor type 2) but with low penetrance (10%-15%), delayed onset (in the third or fourth decade), and a gender bias (two- to fourfold more prevalent in postpubertal women). Thus, investigators have sought an understanding of "second-hit" modalities that might affect BMPR2 anterograde trafficking and/or function. Indeed, vascular lung lesions in PAH have been reported to contain enlarged "vacuolated" endothelial and smooth muscle cells with dilated endoplasmic reticulum (ER) cisternae, increased ER structural protein reticulon 4 (also called Nogo-B), and enlarged and fragmented Golgi apparatus. We recently replicated this cellular phenotype in primary human pulmonary arterial endothelial cells and human pulmonary arterial smooth muscle cells in culture by acute knockdown of the estradiol 17β (E2)-responsive proteins signal transducer and activator of transcription 5a (STAT5a) and STAT5b using small interfering RNAs (siRNAs). We have now investigated whether functional haploinsufficiences of these molecules, alone or in combination with other modalities, might interfere with anterograde membrane trafficking using (a) the quantitative tsO45VSV-G-GFP trafficking assay and (b) assays for cell-surface localization of Flag-tagged BMPR2 molecules. The G glycoprotein of the vesicular stomatitis virus (VSV-G) trafficking assay was validated in EA.hy926 endothelial cells by showing that cells exposed to monocrotaline pyrrole displayed reduced anterograde trafficking. Thereafter, the combinatorial knockdowns of STAT5a, STAT5b, BMPR2, and/or endothelial nitric oxide synthase as well as exposure to E2 or 2-methoxyestradiol were observed to significantly inhibit VSV-G trafficking. These combinations also led to intracellular trapping of wild-type Flag-tagged BMPR2. Overexpression of the PAH disease-derived F14 and KDF mutants of BMPR2, which were trapped in the ER/Golgi, also inhibited VSV-G trafficking in trans. Moreover, probenecid, a chemical chaperone in clinical use today, partially restored cell-surface localization of the KDF but not the F14 mutant. These data identify several combinatorial modalities that inhibit VSV-G anterograde trafficking and cause mislocalization of BMPR2. These modalities merit consideration in defining aspects of the late-developing and gender-biased natural history of human PAH.

Chlamydia trachomatisinfection prevents front-rear polarity of migrating HeLa cells

Chlamydiae are obligate intracellular bacterial pathogens that cause trachoma, sexually transmitted diseases and respiratory infections in humans. Fragmentation of the host cell Golgi apparatus (GA) is essential for chlamydial development, whereas the consequences for host cell functions, including cell migration are not well understood. We could show that Chlamydia trachomatis-infected cells display decelerated migration and fail to repopulate monolayer scratch wounds. Furthermore, infected cells lost the ability to reorient the fragmented GA or the microtubule organization centre (MTOC) after a migratory stimulus. Silencing of golgin-84 phenocopied this defect in the absence of the infection. Interestingly, GA stabilization via knockdown of Rab6A and Rab11A improved its reorientation in infected cells and it was fully rescued after inhibition of Golgi fragmentation with WEHD-fmk. These results show that C. trachomatis infection perturbs host cell migration on multiple levels, including the alignment of GA and MTOC.

Conditional Expression of Parkinson's Disease-Related Mutant -Synuclein in the Midbrain Dopaminergic Neurons Causes Progressive Neurodegeneration and Degradation of Transcription Factor Nuclear Receptor Related 1

α-Synuclein (α-syn) plays a prominent role in the degeneration of midbrain dopaminergic (mDA) neurons in Parkinson's disease (PD). However, only a few studies on α-syn have been performed in the mDA neurons in vivo, which may be attributed to a lack of α-syn transgenic mice that develop PD-like severe degeneration of mDA neurons. To gain mechanistic insights into the α-syn-induced mDA neurodegeneration, we generated a new line of tetracycline-regulated inducible transgenic mice that overexpressed the PD-related α-syn A53T missense mutation in the mDA neurons. Here we show that the mutant mice developed profound motor disabilities and robust mDA neurodegeneration, resembling some key motor and pathological phenotypes of PD. We also systematically examined the subcellular abnormalities that appeared in the mDA neurons of mutant mice and observed a profound decrease of dopamine release, the fragmentation of Golgi apparatus, and the impairments of autophagy/lysosome degradation pathways in these neurons. To further understand the specific molecular events leading to the α-syn-dependent degeneration of mDA neurons, we found that overexpression of α-syn promoted a proteasome-dependent degradation of nuclear receptor-related 1 protein (Nurr1), whereas inhibition of Nurr1 degradation ameliorated the α-syn-induced loss of mDA neurons. Given that Nurr1 plays an essential role in maintaining the normal function and survival of mDA neurons, our studies suggest that the α-syn-mediated suppression of Nurr1 protein expression may contribute to the preferential vulnerability of mDA neurons in the pathogenesis of PD.

Combinatorial inhibitory effects on VSV‐GtsO45GFP trafficking in human endothelial cells due to functional haploinsufficiency of BMPRII, eNOS, STAT5a and STAT5b

Lung lesions in idiopathic pulmonary arterial hypertension (PAH) contain enlarged “vacuolated” endothelial and smooth muscle cells with enlarged and fragmented Golgi apparatus and dilated endoplasmic reticulum (ER) cisternae. Familial PAH often involves mutations in or haploinsuffciency of BMPRII but with low penetrance (10–15%) setting up a search for “second‐hit” genes. Recently we observed that acute knockdown of STAT5a or STAT5b or both in HPAECs using siRNAs led to marked Golgi enlargement and fragmentation and cisternal dilatation of the ER. In the present study we used the VSV‐GtsO45GFP ER to Golgi to plasma membrane trafficking assay in EA.hy926 human endothelial cells to quantitatively assess the combinatorial effects of functional haploinsufficiency of BMPRII, eNOS, STAT5a and STAT5b using respective siRNAs. Knockdown of STAT5a, STAT5b, BMPRII, or eNOS one at a time did not significantly affect intracellular trafficking. However, down‐regulation of STAT5a plus STAT5b inhibited VSV‐G trafficking from the ER/Golgi apparatus to the cell surface by 60–70%. STAT5a or STAT5b combined with eNOS siRNA treatments had a similar inhibitory effect. STAT5a or STAT5b combined with BMPRII siRNA also inhibited VSV‐G trafficking. These observations suggest that combinatorial functional haploinsufficiency of BMPRII, eNOS, STAT5a and STAT5b may contribute to intracellular trafficking defects.

Centrosomal aggregates and Golgi fragmentation disrupt vesicular trafficking of DAT

Lewy bodies containing the centrosomal protein γ-tubulin and fragmentation of Golgi apparatus (GA) have been described in nigral neurons of Parkinson's disease (PD) patients. However, the relevance of these features in PD pathophysiology remains unknown. We analyzed the impact of proteasome inhibition in the formation of γ-tubulin-containing aggregates as well as on GA structure. SH-SY5Y cells were treated with the proteasome inhibitor Z-Leu-Leu-Leu-al (MG132) to induce centrosomal-protein aggregates. Then, microtubules (MTs) and Golgi dynamics, as well as the vesicular transport of dopamine transporter (DAT) were evaluated both in vitro and in living cells. MG132 treatment induced γ-tubulin aggregates which altered microtubule nucleation. MG132-treated cells containing γ-tubulin aggregates showed fragmentation of GA and perturbation of the trans-Golgi network. Under these conditions, the DAT accumulated at the centrosomal-Golgi region indicating that the vesicular transport of DAT was disrupted. Thus, centrosomal aggregates and fragmentation of GA are 2 closely related processes that could result in the disruption of the vesicular transport of DAT toward the plasma membrane in a model of dopaminergic neuronal degeneration.

Clinicopathologic study on an ALS family with a heterozygous E478G optineurin mutation

We investigated a family manifesting amyotrophic lateral sclerosis (ALS) with a heterozygous E478G mutation in the optineurin (OPTN) gene. Clinically, slow deterioration of motor function, mood and personality changes, temporal lobe atrophy on neuroimaging, and bizarre finger deformity were noted. Neuropathologically, TAR DNA-binding protein 43 (TDP-43)-positive neuronal intracytoplasmic inclusions were observed in the spinal and medullary motor neurons. In these cells, the immunoreactivity of nuclear TDP-43 was reduced. Consecutive sections revealed that the inclusions were also reactive with anti-ubiquitin and anti-p62 antibodies, but noticeably negative for OPTN. In addition, TDP-43/p62-positive glial cytoplasmic inclusions (GCIs) were scattered throughout the spinal cord and the medullary motor nuclei. Furthermore, Golgi fragmentation was identified in 70% of the anterior horn cells (AHCs). The presence of AHCs with preserved nuclear TDP-43 and a fragmented Golgi apparatus, which are unrecognizable in sporadic ALS, indicates that patients with the E4787G OPTN mutation would manifest Golgi fragmentation before loss of nuclear TDP-43. In the neocortex, GCIs were sparsely scattered among the primary motor and temporal cortices, but no neuronal TDP-43-positive inclusions were detected. In the amygdala and the ambient gyrus, argyrophilic grains and ballooned neurons were seen. The thorough neuropathologic investigations performed in this work demonstrated that OPTN-positive inclusion bodies, if any, were not prominent. We postulate that optineurinopathy is closely linked with TDP-proteinopathy and speculate that this heterozygous E478G mutation would cause ALS by acting through a dominant-negative mechanism.

Morphological changes of Golgi apparatus in adult rats after facial nerve injuries

We examined the morphological changes of Golgi apparatus (GA) of the facial motor neurons in rats after facial nerve avulsion or axotomy. In rats after avulsion, the numbers of motor neurons showed reduction and fragmentation of GA, namely the organelle lost the normal network-like configuration which was replaced by numerous small disconnected elements (fine fragmentation). This GA fragmentation was morphologically indistinguishable from that previously reported in amyotrophic lateral sclerosis (ALS). On the other hand, axotomy did not induce significant motor neuron loss, and the GA had lost the elongated profiles (coarse fragmentation). These results suggest that there may be a similar cascade leading to motor neuron death in rats after avulsion, and ALS and GA observed in rats after axotomy may not be related to neuronal death.