Evidence for lysosomal biogenesis proteome defect and impaired autophagy in preeclampsia

The etiology of preeclampsia (PE), a serious pregnancy complication, remains an enigma. We have demonstrated that proteinopathy, a pathologic feature of neurodegenerative diseases, is a key observation in the placenta and serum from PE patients. We hypothesize that the macroautophagy/autophagy machinery that mediates degradation of aggregated proteins and damaged organelles is impaired in PE. Here, we show that TFEB (transcription factor EB), a master transcriptional regulator of lysosomal biogenesis, and its regulated proteins, LAMP1, LAMP2, and CTSD (cathepsin D), were dysregulated in the placenta from early and late onset PE deliveries. Primary human trophoblasts and immortalized extravillous trophoblasts (EVTs) showed reduced TFEB expression and nuclear translocation as well as lysosomal protein content in response to hypoxia. Hypoxia-exposed trophoblasts also showed decreased PPP3/calcineurin phosphatase activity and increased XPO1/CRM1 (exportin 1), events that inhibit TFEB nuclear translocation. These proteins were also dysregulated in the PE placenta. These results are supported by observed lysosomal ultrastructural defects with decreased number of autolysosomes in hypoxia-treated primary human trophoblasts. Autophagy-deficient human EVTs exhibited poor TFEB nuclear translocation, reduced lysosomal protein expression and function, and increased MTORC1 activity. Sera from PE patients induced these features and protein aggregation in EVTs. Importantly, trophoblast-specific conditional atg7 knockout mice exhibited reduced TFEB expression with increased deposition of protein aggregates in the placenta. These results provide compelling evidence for a regulatory link between accumulation of protein aggregates and TFEB-mediated impaired lysosomal biogenesis and autophagy in the placenta of PE patients. Abbreviation:atg7: autophagy related 7; CTSD: cathepsin D; ER: endoplasmic reticulum; EVTs: extravillous trophoblasts; KRT7: keratin 7; LAMP1: lysosomal associated membrane protein 1; LAMP2: lysosomal associated membrane protein 2; mSt: mStrawberry; MTORC1: mechanistic target of rapamycin complex 1; NP: normal pregnancy; NPS: normal pregnancy serum; PE: preeclampsia; PES: preeclampsia serum; p-RPS6KB: phosphorylated ribosomal protein S6 kinase B1; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy; TFEB: transcription factor EB; XPO1/CRM1: exportin 1.

The gene for the lysosomal protein LAMP3 is a direct target of the transcription factor ATF4

Autophagy and lysosomal activities play a key role in the cell by initiating and carrying out the degradation of misfolded proteins. Transcription factor EB (TFEB) functions as a master controller of lysosomal biogenesis and function during lysosomal stress, controlling most but, importantly, not all lysosomal genes. Here, we sought to better understand the regulation of lysosomal genes whose expression does not appear to be controlled by TFEB. Sixteen of these genes were screened for transactivation in response to diverse cellular insults. mRNA levels for lysosomal-associated membrane protein 3 (LAMP3), a gene that is highly up-regulated in many forms of cancer, including breast and cervical cancers, were significantly increased during the integrated stress response, which occurs in eukaryotic cells in response to accumulation of unfolded and misfolded proteins. Of note, results from siRNA-mediated knockdown of activating transcription factor 4 (ATF4) and overexpression of exogenous ATF4 cDNA indicated that ATF4 up-regulates LAMP3 mRNA levels. Finally, ChIP assays verified an ATF4-binding site in the LAMP3 gene promoter, and a dual-luciferase assay confirmed that this ATF4-binding site is indeed required for transcriptional up-regulation of LAMP3 These results reveal that ATF4 directly regulates LAMP3, representing the first identification of a gene for a lysosomal component whose expression is directly controlled by ATF4. This finding may provide a key link between stresses such as accumulation of unfolded proteins and modulation of autophagy, which removes them.

Oral Delivery of the P2Y12 Receptor Antagonist Ticagrelor Prevents Loss of Photoreceptors in an ABCA4-/- Mouse Model of Retinal Degeneration

Purpose

Accumulation of lysosomal waste is linked to neurodegeneration in multiple diseases, and pharmacologic enhancement of lysosomal activity is hypothesized to reduce pathology. An excessive accumulation of lysosomal-associated lipofuscin waste and an elevated lysosomal pH occur in retinal pigment epithelial cells of the ABCA4-/- mouse model of Stargardt's retinal degeneration. As treatment with the P2Y12 receptor antagonist ticagrelor was previously shown to lower lysosomal pH and lipofuscin-like autofluorescence in these cells, we asked whether oral delivery of ticagrelor also prevented photoreceptor loss.

Methods

Moderate light exposure was used to accelerate photoreceptor loss in albino ABCA4-/- mice as compared to BALB/c controls. Ticagrelor (0.1%-0.15%) was added to mouse chow for between 1 and 10 months. Photoreceptor function was determined with electroretinograms, while cell survival was determined using optical coherence tomography and histology.

Results

Protection by ticagrelor was demonstrated functionally by using the electroretinogram, as ticagrelor-treated ABCA4-/- mice had increased a- and b-waves compared to untreated mice. Mice receiving ticagrelor treatment had a thicker outer nuclear layer, as measured with both optical coherence tomography and histologic sections. Ticagrelor decreased expression of LAMP1, implicating enhanced lysosomal function. No signs of retinal bleeding were observed after prolonged treatment with ticagrelor.

Conclusions

Oral treatment with ticagrelor protected photoreceptors in the ABCA4-/- mouse, which is consistent with enhanced lysosomal function. As mouse ticagrelor exposure levels were clinically relevant, the drug may be of benefit in preventing the loss of photoreceptors in Stargardt's disease and other neurodegenerations associated with lysosomal dysfunction.

LIN28A inhibits lysosome‑associated membrane glycoprotein 1 protein expression in embryonic stem and bladder cancer cells

Tumor cells and embryonic stem cells (ESCs) have similar transcription mechanisms. LIN28A is an important factor in tumor cells and ESCs, it is an inhibitor of intracellular endoplasmic reticulum (ER)‑related protein translation in ESCs. The present study aimed to examine the effects of LIN28A on an ER‑related protein, lysosome‑associated membrane glycoprotein 1 (LAMP1), in human bladder cancer cells and mouse (m)ESCs, using reverse transcription‑quantitative polymerase chain reaction and western blotting to detect the expression of LAMP1 mRNA and protein, respectively, following LIN28A knockdown. LIN28A was revealed to promote the proliferation, migration and invasion in human bladder cancer cells. These data suggested similarities between ESC cells and cancer cells and may provide novel ideas for the use of induced embryonic stem cell differentiation to treat tumors.

6-Hydroxydopamine induces autophagic flux dysfunction by impairing transcription factor EB activation and lysosomal function in dopaminergic neurons and SH-SY5Y cells

Autophagy deregulation has been implicated in Parkinson's disease (PD), yet the role of autophagy in neuronal survival remains controversial. In this study, we comprehensively investigated the time-course of autophagy-related markers in 6-OHDA-induced Parkinsonian rat models and assessed its effect on the state of autophagic flux both in vivo and in vitro. We observed an early activation of autophagy followed by autophagic flux impairment, which was confirmed with autophagy inhibitor chloroquine in vivo and Ad-GFP-mCherry-LC3-infected SH-SY5Y cells in vitro. In addition, 6-OHDA not only remarkably reduced the expression level of lysosome-associated membrane protein 1 (Lamp1), but also impaired the hydrolase activities of lysosomal proteases. Transcription factor EB (TFEB), a key transcription factor controlling lysosome biogenesis, was also significantly downregulated by 6-OHDA and its nuclear translocation was inhibited as well, which could account for the impaired lysosomal function. Promoting lysosome biogenesis through TFEB overexpression could protect SH-SY5Y cells against 6-OHDA-induced neurotoxicity. The above findings demonstrated that autophagic flux dysfunction was closely associated with 6-OHDA-induced neurotoxicity and highlighted the importance of functional lysosomes and homeostatic autophagic flux in developing therapeutic agents for PD.

Morphological characteristics of fatal pediatric hand, foot and mouth disease: A clinicopathological study with related receptors of EV71

OBJECTIVE

To investigate the pathological features of fatal pediatric hand foot and mouth disease (HFMD).

METHODS

The histopathological features of HFMD were first summarized from literature, and then confirmed by in-house autopsies. Furthermore, immunohistochemistry was conducted to detect the distribution and expression level of two enterovirus 71 (EV71) receptors scavenger receptor class B, member 2 (SCARB2), and P-selectin glycoprotein ligand-1 (PSGL1) in the samples of autopsies.

RESULTS

The main symptoms of HFMD included hand and foot rashes, as well as oral herpes. The fatal HFMD patients had typical histopathological change in the central nervous system, such as encephaledema and encephalitis. As for respiratory system, the fatal HFMD patients suffered acute pulmonary edema and congestion. SCARB2 positive signaling was distributed equally in bronchial and bronchiolar epithelial cells, alveolar epithelial cells and inflammatory cells of all HFMD patients, healthy children and adults without significant difference. PSGL-1 dispersed in bronchial and bronchiolar epithelial cells of healthy adults, but no PSGL-1 expression was detected in HFMD patients and healthy children.

CONCLUSIONS

Both of the central nervous and respiratory systems may be involved in the fatal HFMD patients. The EV71 receptor PSGL-1 might play essential parts in the pathogenesis of fatal HFMD, however, the hypothesis needs to be further investigated.

Altered expression of lysosomal associated membrane protein 1 in esophageal squamous cell carcinoma

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers. LAMP1, major protein components of lysosome, is primarily located on the lysosomal membrane and rarely expressed on the surface of normal cells, playing an important role in the lysosome-mediated physiological processes. Previous studies confirmed that LAMP1 showed high expression in astrocytoma. The purpose of this study was to investigate the expression levels of LAMP1 and to discuss its roles in ESCC.

METHODS

We collected 610 tissue samples of ESCC patients to construct tissue microarrays, which were subsequently stained by immunohistochemistry with LAMP1 antibody.

RESULTS

After immunohistochemical staining, a total of 584 patients, including 453 men and 131 women, were analysed. The positive immunostaining was mainly located at the cytoplasm. The LAMP1 expression levels were significantly different between different T status (P<0.001), TNM stages (P<0.01) and degrees of tumor histological differentiation (P<0.001). Besides, LAMP1 expression levels were positively correlated with TNM stages (P<0.05). The higher the TNM stages, the higher the LAMP1 expression levels. Similar results also appeared in degrees of tumor histological differentiation (P<0.01), but not in ages, genders, tumor size, T status, lymphatic metastasis and tumor locations (P>0.05).

CONCLUSION

LAMP1 is involved in the TNM stages and histological differentiation of the ESCC. Targeted therapy for LAMP1 may be a promising novel therapeutic strategy against poorly differentiated ESCC.

LAMP3 expression correlated with poor clinical outcome in human ovarian cancer

Lysosome-associated membrane protein 3 belongs to the lysosome-associated membrane glycoprotein family, which is associated with lymph node, metastasis, poor overall survival, and resistance to chemotherapy and radiotherapy. Epithelial ovarian cancer is one of the most deadly global female gynecologic malignant tumors. Its clinical outcome is poor and most epithelial ovarian cancer patients tend to relapse because of drug resistance. However, lysosome-associated membrane protein 3 expression in epithelial ovarian cancer and its relationship between clinicopathologic factors remain poorly understood. To clarify the prognostic implications of lysosome-associated membrane protein 3 in epithelial ovarian cancer, we analyzed both messenger RNA and protein levels of lysosome-associated membrane protein 3 in ovarian carcinomas. Polymerase chain reaction results showed higher expression of lysosome-associated membrane protein 3 messenger RNA in epithelial ovarian cancer than in noncancerous tissues. Immunohistochemical results showed that high lysosome-associated membrane protein 3 cytoplasmic expression was significantly related to tumor grade ( p = 0.038), lymph node metastasis ( p = 0.049), metastasis ( p < 0.001), level of CA125 ( p = 0.030), and International Federation of Gynecology and Obstetrics (FIGO) ( p < 0.001). High lysosome-associated membrane protein 3 nuclear expression was significantly associated with tumor grade ( p = 0.046), tumor single or double (representative whether the tumor involving one or both ovaries) ( p = 0.016), metastasis ( p < 0.001), and FIGO stage ( p < 0.001). Survival analysis indicated that high lysosome-associated membrane protein 3 cytoplasmic expression (hazard ratio: 4.632, 95% confidence interval: 2.421-8.864; p < 0.001), patients' age (hazard ratio: 1.729, 95% confidence interval: 1.027-2.911; p = 0.039), and FIGO stage (hazard ratio: 2.049, 95% confidence interval: 1.113-3.774; p = 0.021) were significantly correlated with poor survival outcome of epithelial ovarian cancer patients.

Dysfunctional autophagy in RPE, a contributing factor in age-related macular degeneration

Age-related macular degeneration (AMD) is a devastating neurodegenerative disease and a major cause of blindness in the developed world. Owing to its complexity and the lack of an adequate human model that recapitulates key aspects of the disease, the molecular mechanisms of AMD pathogenesis remain poorly understood. Here we show that cultured human retinal pigment epithelium (RPE) from AMD donors (AMD RPE) are functionally impaired and exhibit distinct phenotypes compared with RPE cultured from normal donors (normal RPE). Accumulation of lipid droplets and glycogen granules, disintegration of mitochondria, and an increase in autophagosomes were observed in AMD RPE cultures. Compared with normal RPE, AMD RPE exhibit increased susceptibility to oxidative stress, produce higher levels of reactive oxygen species (ROS) under stress conditions, and showed reduced mitochondrial activity. Measurement of the ratio of LC3-II/ LC3-I, revealed impaired autophagy in AMD RPE as compared with normal RPE. Autophagic flux was also reduced in AMD RPE as compared with normal RPE, as shown by inability of AMD RPE to downregulate p62 levels during starvation. Impaired autophagic pathways were further shown by analyzing late autophagic vesicles; immunostaining with lysosome-associated membrane protein 1 (LAMP-1) antibody revealed enlarged and annular LAMP-1-positive organelles in AMD RPE as opposed to smaller discrete puncta observed in normal RPE. Our study provides insights into AMD cellular and molecular mechanisms, proposes dysfunctional autophagy as an underlying mechanism contributing to the pathophysiology of the disease, and opens up new avenues for development of novel treatment strategies.

LAMP1 expression is associated with malignant behaviours and predicts unfavourable prognosis in laryngeal squamous cell carcinoma

Lysosome-associated membrane protein-1 (LAMP1) has been suggested to play complicated roles in cancer development and metastasis. The aim of this study was to explore the expression of LAMP1 in laryngeal squamous cell carcinoma (LSCC) and investigate the relationship between LAMP1 expression and clinicopathological characteristics in LSCC patients. One-step quantitative reverse transcription PCR (qPCR) tests (20 fresh LSCC and non-cancerous tissue samples) and immunohistochemistry (IHC) analyses (137 paraffin-embedded LSCC and non-cancerous tissue samples) were performed to evaluate the LAMP1 expression in both mRNA and protein levels. Results showed that the expression of LAMP1 in LSCC tissues was significantly higher than that in non-cancerous tissues. Furthermore, the expression level of LAMP1 protein was statistically associated with lymph node metastasis and TNM stage. Results of Kaplan-Meier survival and Cox regression analyses revealed that LSCC patients with high LAMP1 cytoplasmic expression (p=0.044), high cytoplasmic+low mesenchymal expression of LAMP1 (H+L) (p=0.015) and histopathological grade (p=0.014) encountered poor overall survival. The data implied that high LAMP1 expression is associated with unfavourable prognosis in LSCC patients, and LAMP1 may be identified as a novel prognostic biomarker.

Lysosome-associated membrane proteins-1 and -2 (LAMP-1 and LAMP-2) assemble via distinct modes

Lysosome-associated membrane proteins 1 and 2 (LAMP-1 and LAMP-2) have a large, heavily glycosylated luminal domain composed of two subdomains, and are the most abundant protein components in lysosome membranes. LAMP-1 and LAMP-2 have distinct functions, and the presence of both proteins together is required for the essential regulation of autophagy to avoid embryonic lethality. However, the structural aspects of LAMP-1 and LAMP-2 have not been elucidated. In the present study, we demonstrated that the subdomains of LAMP-1 and LAMP-2 adopt the unique β-prism fold, similar to the domain structure of the dendritic cell-specific-LAMP (DC-LAMP, LAMP-3), confirming the conserved aspect of this family of lysosome-associated membrane proteins. Furthermore, we evaluated the effects of the N-domain truncation of LAMP-1 or LAMP-2 on the assembly of LAMPs, based on immunoprecipitation experiments. We found that the N-domain of LAMP-1 is necessary, whereas that of LAMP-2 is repressive, for the organization of a multimeric assembly of LAMPs. Accordingly, the present study suggests for the first time that the assembly modes of LAMP-1 and LAMP-2 are different, which may underlie their distinct functions.

Direct regulation of LAMP1 by tumor-suppressive microRNA-320a in prostate cancer

Advanced prostate cancer (PCa) metastasizes to bone and lymph nodes, and currently available treatments cannot prevent the progression and metastasis of the disease. Therefore, an improved understanding of the molecular mechanisms of the progression and metastasis of advanced PCa using current genomic approaches is needed. Our miRNA expression signature in castration-resistant prostate cancer (CRPC) revealed that microRNA-320a (miR‑320a) was significantly reduced in cancer tissues, suggesting that miR‑320a may be a promising anticancer miRNA. The aim of this study was to investigate the functional roles of miR‑320a in naïve PCa and CRPC cells and to identify miR‑320a-regulated genes involved in PCa metastasis. The expression levels of miR‑320a were significantly reduced in naïve PCa, CRPC specimens, and PCa cell lines. Restoration of mature miR‑320a in PCa cell lines showed that miR‑320a significantly inhibited cancer cell migration and invasion. Moreover, we found that lysosomal-associated membrane protein 1 (LAMP1) was a direct target of miR‑320a in PCa cells. Silencing of LAMP1 using siRNA significantly inhibited cell proliferation, migration, and invasion in PCa cells. Overexpression of LAMP1 was observed in PCa and CRPC clinical specimens. Moreover, downstream pathways were identified using si-LAMP1-transfected cells. The discovery of tumor-suppressive miR‑320a-mediated pathways may provide important insights into the potential mechanisms of PCa metastasis.

Cardiac Kinetophagy Coincides with Activation of Anabolic Signaling

PURPOSE

Growing evidence has shown that endurance exercise is a strong inducer of autophagy in various tissues. Thus, we define here endurance exercise-induced autophagy as "kinetophagy" derived from the Greek terms "kineto" (movement), "auto" (self), and "phagy" (eating). Currently, the exact cellular mechanisms responsible for kinetophagy remain unclear; hence, we examined kinetophagy signaling transduction pathways occurring during acute endurance exercise (AEE).

METHODS

C57BL/6 mice were randomly assigned to either AEE (n = 7) or control sedentary group (CON, n = 7). After 5 d of treadmill running acclimation, mice performed 60 min of a single bout of treadmill running at 12 m · min(-1) on a 0% grade. Hearts were excised immediately 1 h after exercise and homogenized for Western blot analyses.

RESULTS

Our data showed that AEE promoted kinetophagy flux (an increase in LC3-II to LC3-I ratio and LC3-II levels and a reduction in p62 levels) with Beclin-1 levels suppressed but Atg7 levels elevated compared with those in the sedentary group. We also observed that AEE increased lysosome-associated membrane protein and cathepsin L, linked to the termination process of autophagy, and that AEE augmented potent autophagy inducers (i.e., adenosine monophosphate kinase phosphorylation, BNIP3, and HSP70). Moreover, we found that exercise-mediated BNIP3 upregulation is associated with hypoxia-inducing factor 1α rather than FoxO3a. Intriguingly, we found for the first time that kinetophagy parallels with anabolic signaling activation (Akt and mammalian target of rapamycin).

CONCLUSIONS

Our findings provide evidence that AEE results in kinetophagy without a time-associated elevation in Beclin-1 but with the presence of Akt-mTOR activation and that AEE-induced activation of anabolic signaling is not associated with kinetophagy promotion.

Nanoparticles modulate autophagic effect in a dispersity-dependent manner

Autophagy plays a key role in human health and disease, especially in cancer and neurodegeneration. Many autophagy regulators are developed for therapy. Diverse nanomaterials have been reported to induce autophagy. However, the underlying mechanisms and universal rules remain unclear. Here, for the first time, we show a reliable and general mechanism by which nanoparticles induce autophagy and then successfully modulate autophagy via tuning their dispersity. Various well-designed univariate experiments demonstrate that nanomaterials induce autophagy in a dispersity-dependent manner. Aggregated nanoparticles induce significant autophagic effect in comparison with well-dispersed nanoparticles. As the highly stable nanoparticles may block autophagic degradation in autolysosomes, endocytosis and intracellular accumulation of nanoparticles can be responsible for this interesting phenomenon. Our results suggest dispersity-dependent autophagic effect as a common cellular response to nanoparticles, reveal the relationship between properties of nanoparticles and autophagy, and offer a new alternative way to modulate autophagy.

High Expression of LAMP3 Is a Novel Biomarker of Poor Prognosis in Patients with Esophageal Squamous Cell Carcinoma

Lysosomal-associated membrane protein 3 (LAMP3), identified as a molecular marker of mature dendritic cells, is one of the LAMP family members. Its expression was induced by hypoxia, and was associated with hypoxia mediated metastasis in breast and cervical cancers. However, epithelial expression of LAMP3 and its prognostic value in esophageal squamous cell carcinoma (ESCC) is still unknown. In the current study, mRNA expression of LAMP3 in 157 ESCC tissues and 50 adjacent normal tissues was detected by quantitative real-time PCR (qRT-PCR). LAMP3 protein expression in 46 paired cancerous and normal tissues was detected by immunohistochemistry (IHC). Then, DNA copy number was examined to observe its potential correlation with mRNA expression. The results showed that both mRNA and protein expression level of LAMP3 was significantly higher in cancerous tissues compared with normal controls (p < 0.001). LAMP3 DNA copy number was amplified in 70% of ESCC tissues and positive correlated with mRNA expression (p = 0.037). Furthermore, patients with higher LAMP3 expression had worse overall survival (HR = 1.90, 95% CI = 1.17-3.09, p = 0.010) and disease-free survival (HR = 1.80, 95% CI = 1.18-2.74, p = 0.006). In conclusion, our results suggest that epithelial LAMP3 expression is an independent prognostic biomarker for ESCC.

Thrombin-induced lysosomal exocytosis in human platelets is dependent on secondary activation by ADP and regulated by endothelial-derived substances

Exocytosis of lysosomal contents from platelets has been speculated to participate in clearance of thrombi and vessel wall remodelling. The mechanisms that regulate lysosomal exocytosis in platelets are, however, still unclear. The aim of this study was to identify the pathways underlying platelet lysosomal secretion and elucidate how this process is controlled by platelet inhibitors. We found that high concentrations of thrombin induced partial lysosomal exocytosis as assessed by analysis of the activity of released N-acetyl-β-glucosaminidase (NAG) and by identifying the fraction of platelets exposing the lysosomal-associated membrane protein (LAMP)-1 on the cell surface by flow cytometry. Stimulation of thrombin receptors PAR1 or PAR4 with specific peptides was equally effective in inducing LAMP-1 surface expression. Notably, lysosomal exocytosis in response to thrombin was significantly reduced if the secondary activation by ADP was inhibited by the P2Y12 antagonist cangrelor, while inhibition of thromboxane A2 formation by treatment with acetylsalicylic acid was of minor importance in this regard. Moreover, the NO-releasing drug S-nitroso-N-acetyl penicillamine (SNAP) or the cyclic AMP-elevating eicosanoid prostaglandin I2 (PGI2) significantly suppressed lysosomal exocytosis. We conclude that platelet inhibitors that mimic functional endothelium such as PGI2 or NO efficiently counteract lysosomal exocytosis. Furthermore, we suggest that secondary release of ADP and concomitant signaling via PAR1/4- and P2Y12 receptors is important for efficient platelet lysosomal exocytosis by thrombin.

Anti-β₂-microglobulin monoclonal antibodies overcome bortezomib resistance in multiple myeloma by inhibiting autophagy

Our previous studies showed that anti-β2M monoclonal antibodies (mAbs) have strong and direct apoptotic effects on multiple myeloma (MM) cells, suggesting that anti-β2M mAbs might be developed as a novel therapeutic agent. In this study, we investigated the anti-MM effects of combination treatment with anti-β2M mAbs and bortezomib (BTZ). Our results showed that anti-β2M mAbs enhanced BTZ-induced apoptosis of MM cell lines and primary MM cells. Combination treatment could also induce apoptosis of BTZ-resistant MM cells, and the enhanced effect depended on the surface expression of β2M on MM cells. BTZ up-regulated the expression of autophagy proteins, whereas combination with anti-β2M mAbs inhibited autophagy. Sequence analysis of the promoter region of beclin 1 identified 3 putative NF-κB-binding sites from -615 to -789 bp. BTZ treatment increased, whereas combination with anti-β2M mAbs reduced, NF-κB transcription activities in MM cells, and combination treatment inhibited NF-κB p65 binding to the beclin 1 promoter. Furthermore, anti-β2M mAbs and BTZ combination treatment had anti-MM activities in an established MM mouse model. Thus, our studies provide new insight and support for the clinical development of an anti-β2M mAb and BTZ combination treatment to overcome BTZ drug resistance and improve MM patient survival.

Prognostic value of LAMP3 and TP53 overexpression in benign and malignant gastrointestinal tissues

Lysosomal associated membrane protein 3 (LAMP3) is a newly identified tumor-specific protein. It is a downstream target gene of tumor suppressor TP53 and its expression has been associated with hypoxia-induced metastasis and poor overall survival in cervical and breast cancers. However, little is known of LAMP3 protein expression in gastrointestinal cancer and its prognostic value. We determined protein expression of LAMP3 and TP53 in both gastric (n=750) and colorectal (n=479) tissues by immunohistochemistry analysis on tissue microarray (TMA), their expression was correlated with patients' clinical parameters. LAMP3 and TP53 protein expression was significantly higher in cancerous tissues compared to normal and benign tissues. In both gastric and colorectal cancers, high LAMP3 protein expression (LAMP3+) was significantly associated with tumor stage (P=0.014 and P<0.001). No correlation between LAMP3 and TP53 expression was observed. Patients with high LAMP3 expression but not high TP53 expression had a poor overall survival (for gastric cancer P<0.001, CI: 1.762-4.567; for colorectal cancer P=0.036, CI: 1.062-5.980). Our data suggest that epithelial LAMP3 expression is an independent prognostic marker for gastrointestinal cancer.

Detailed characterization of the endocannabinoid system in human macrophages and foam cells, and anti-inflammatory role of type-2 cannabinoid receptor

OBJECTIVE

Cannabinoid receptors are activated in murine macrophages upon exposure to oxidized low-density lipoproteins (oxLDL), and type-1 cannabinoid receptor (CB1R) is considered as a risk factor in atherosclerosis, because it promotes cholesterol accumulation and release of inflammatory mediators. Conversely, accumulated evidence suggests a protective role for type-2 cannabinoid receptor (CB2R). Here, we sought to ascertain whether different elements of the endocannabinoid system (ECS) were activated in human lipid-laden macrophages, and whether CB2R played any role in atherogenesis and inflammation of these cells.

METHODS AND RESULTS

Human macrophages were exposed to oxLDL in order to obtain lipid-laden foam cells. Liquid chromatography/mass spectrometry (LC/MS) was used to measure the production of the endocannabinoids in both macrophages and foam cells, and radiometric assays were performed to measure cannabinoid receptor binding and activity of endocannabinoid metabolizing enzymes. OxLDL accumulation was investigated by confocal imaging, and cytokine production and release were measured by means of flow cytometry and ELISA. The results showed that human macrophages possess a fully functional ECS, which was modulated by oxLDL. Selective CB2R activation reduced cellular oxLDL accumulation, which was associated with decreased expression of CD36 scavenger receptor, and decreased production of TNFα, IL-12 and IL-10. These anti-atherogenic and anti-inflammatory effects were reverted by the selective CB2R antagonist SR144528.

CONCLUSIONS

A fully active ECS is present in human macrophages and macrophage-derived foam cells. Selective activation of CB2R reduces CD36-dependent oxLDL accumulation and modulates production of inflammatory cytokines, thus representing a potential therapeutic strategy to combat atherosclerosis.

Establishment of cell lines with increased susceptibility to EV71/CA16 by stable overexpression of SCARB2

BACKGROUND

Human enterovirus type 71 (EV71) and Coxsackievirus A group type 16 (CA16) belong to human Enterovirus species A of the family Picornaviridae. These viruses are recognized as the major pathogens responsible for epidemics of hand-foot-mouth disease (HFMD), which presents with fever and vesicular eruptions of palms, soles of the feet or mouth. Human scavenger receptor class B, member 2 (SCARB2) has been identified as the receptor for both EV71 and CA16, as overexpression of SCARB2 in cells can enhance virus replication significantly.

METHODS

In this study, we used a lentivirus packaging vector to transduce the SCARB2 gene into human embryonic kidney cells (293), human rhabdomyosarcoma cells (RD) and African green monkey kidney cells (Vero) to create stable expression lines. Expression of SCARB2 in the resulting three transgenic cell lines was confirmed by real-time RT-PCR, immunofluorescence and flow cytometry.

RESULTS

Levels of SCARB2 mRNA determined by real-time RT-PCR in 293-SCARB2 (293S) or RD-SCARB2 (RDS) transgenic cell lines were approximately 2 × 10(2) times higher than those in 293 and RD cells, respectively, and three times higher in Vero-SCARB2 (VeroS) than in Vero cells. Furthermore, EV71 and CA16 virus titers in 293S and RDS cells were 10(2)-10(3)-fold higher (detected in RD cell) than those in the parental cells, and a 10-fold higher titer of EV71 was achieved in VeroS cells compared with that in Vero cells.

CONCLUSIONS

We established for the first time three cell lines stably overexpressing SCARB2, which showed drastic increases in susceptibility to EV71/CA16 infection. These optimal cell lines may be utilized to develop inactivated vaccines for EV71/CA16 and facilitate rapid detection and isolation of HFMD pathogens or other Enterovirus serotypes. Furthermore, these stable cell lines also can serve as tools to facilitate drug screenings as well as molecular studies on virus-host interactions and pathogenesis of causative agents for HFMD.

A multilevel screening strategy defines a molecular fingerprint of proregenerative olfactory ensheathing cells and identifies SCARB2, a protein that improves regenerative sprouting of injured sensory spinal axons

Olfactory ensheathing cells (OECs) have neuro-restorative properties in animal models for spinal cord injury, stroke, and amyotrophic lateral sclerosis. Here we used a multistep screening approach to discover genes specifically contributing to the regeneration-promoting properties of OECs. Microarray screening of the injured olfactory pathway and of cultured OECs identified 102 genes that were subsequently functionally characterized in cocultures of OECs and primary dorsal root ganglion (DRG) neurons. Selective siRNA-mediated knockdown of 16 genes in OECs (ADAMTS1, BM385941, FZD1, GFRA1, LEPRE1, NCAM1, NID2, NRP1, MSLN, RND1, S100A9, SCARB2, SERPINI1, SERPINF1, TGFB2, and VAV1) significantly reduced outgrowth of cocultured DRG neurons, indicating that endogenous expression of these genes in OECs supports neurite extension of DRG neurons. In a gain-of-function screen for 18 genes, six (CX3CL1, FZD1, LEPRE1, S100A9, SCARB2, and SERPINI1) enhanced and one (TIMP2) inhibited neurite growth. The most potent hit in both the loss- and gain-of-function screens was SCARB2, a protein that promotes cholesterol secretion. Transplants of fibroblasts that were genetically modified to overexpress SCARB2 significantly increased the number of regenerating DRG axons that grew toward the center of a spinal cord lesion in rats. We conclude that expression of SCARB2 enhances regenerative sprouting and that SCARB2 contributes to OEC-mediated neuronal repair.

Expression of the transmembrane lysosomal protein SCARB2/Limp-2 in renin secretory granules controls renin release

BACKGROUND/AIMS

Renin processing and storage is believed to occur in lysosome-like structures in the afferent arteriole. SCARB2/Limp-2 is a transmembrane lysosomal protein responsible for the intracellular trafficking of β-glucocerebrosidase. This study aimed to confirm the expression of SCARB2/Limp-2 in renin secretory granules, and explore its role in renin processing and secretion.

METHODS

Co-localisation studies of (pro)renin with lysosomal membrane proteins, SCARB2/Limp-2, LAMP-1 and LAMP-2, were performed in mouse and human kidney sections. Intrarenal expression and secretion of (pro)renin in wild-type (WT) and Limp-2(-/-) mice were compared with and without stimulation.

RESULTS

SCARB2/Limp-2, LAMP-1 and LAMP-2 co-localised with (pro)- renin in mouse and human kidney. Plasma renin concentration was increased in Limp-2(-/-) mice when compared to WT littermates. No change in (pro)renin expression, however, was observed in Limp-2(-/-) mouse kidney cortex by immunofluorescence microscopy, Western blotting, quantitative RT-PCR or the ultrastructural appearance of renin secretory granules. Acute stimulation of renin release by isoprenaline or hydralazine was similar in WT and Limp-2(-/-) mice. Following chronic salt restriction, however, immunofluorescence microscopy showed less (pro)renin expressed in Limp-2(-/-) compared with WT mouse kidneys, and there was significantly less prorenin but not renin by Western blotting in Limp-2(-/-) mouse kidney cortex, despite no difference in circulating renin levels.

CONCLUSION

Renin secretory granules possess integral lysosomal proteins, confirming that they are indeed modified lysosomes. Limp-2 deficiency leads to a minor increase in circulating renin. Limp-2, however, is not required for acute or chronic stimulation of renin release.

Hypoxia stimulates migration of breast cancer cells via the PERK/ATF4/LAMP3-arm of the unfolded protein response

INTRODUCTION

The hypoxia-inducible factor (HIF)-1 pathway can stimulate tumor cell migration and metastasis. Furthermore, hypoxic tumors are associated with a poor prognosis. Besides the HIF-1 pathway, the unfolded protein response (UPR) is also induced by hypoxic conditions. The PKR-like ER kinase (PERK)/activating transcription factor 4 (ATF4)-arm of the UPR induces expression of lysosomal-associated membrane protein 3 (LAMP3), a factor that has been linked to metastasis and poor prognosis in solid tumors. In this study the role of UPR-induced LAMP3 in hypoxia-mediated migration of breast cancer cells was examined.

METHODS

A number of in vitro metastasis models were used to study the migration and invasion of MDA-MB-231 breast cancer cells under hypoxic conditions. PERK, ATF4 and their downstream factor LAMP3 were knocked down to examine their role in cell migration. In addition, multicellular tumor spheroids were used to study the involvement of the tumor microenvironment in invasion.

RESULTS

Using transwell assays, migration of different breast cancer cell lines was assessed. A direct correlation was found between cell migration and baseline LAMP3 expression. Furthermore, moderate hypoxia (1% O2) was found to be optimal in stimulating migration of MDA-MB-231 cells. siRNA mediated knockdown of PERK, ATF4 and LAMP3 reduced migration of cells under these conditions. Using gap closure assays, similar results were found. In a three-dimensional invasion assay into collagen, LAMP3 knockdown cells showed a diminished capacity to invade compared to control cells when collectively grown in multicellular spheroids.

CONCLUSIONS

Thus, the PERK/ATF4/LAMP3-arm of the UPR is an additional pathway mediating hypoxia-induced breast cancer cell migration.

Glucocerebrosidase mutations alter the endoplasmic reticulum and lysosomes in Lewy body disease

Lewy body disease (LBD) development is enhanced by mutations in the GBA gene coding for glucocerebrosidase (GCase). The mechanism of this association is thought to involve an abnormal lysosomal system and we therefore sought to evaluate if lysosomal changes contribute to the pathogenesis of idiopathic LBD. Analysis of post-mortem frontal cortex tissue from 7 GBA mutation carriers with LBD, 5 GBA mutation carriers with no signs of neurological disease and human neural stem cells exposed to a GCase inhibitor was used to determine how GBA mutation contributes to LBD. GBA mutation carriers demonstrated a significantly reduced level of GCase protein and enzyme activity and retention of glucocerebrosidase isoforms within the endoplasmic reticulum (ER). This was associated with enhanced expression of the lysosomal markers LAMP1 and LAMP2, though the expression of ATP13A2 and Cathepsin D was reduced, along with the decreased activity of Cathepsin D. The ER unfolded protein response (UPR) regulator BiP/GRP78 was reduced by GBA mutation and this was a general phenomenon in LBD. Despite elevation of GRP94 in LBD, individuals with GBA mutations showed reduced GRP94 expression, suggesting an inadequate UPR. Finally, human neural stem cell cultures showed that inhibition of GCase causes acute reduction of BiP, indicating that the UPR is affected by reduced glucocerebrosidase activity. The results indicate that mutation in GBA leads to additional lysosomal abnormalities, enhanced by an impaired UPR, potentially causing α-synuclein accumulation.

Altered expression of autophagic genes in the peripheral leukocytes of patients with sporadic Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disease caused by interaction of genetic and environmental factors. To date, genetic genes and variants causing PD remain largely unknown. Autophagy is a conserved cellular process including three subtypes, macroautophagy (hereafter referred to as autophagy), microautophagy and chaperone-mediated autophagy (CMA). Although reduced CMA and induced autophagy are observed in human PD brain samples, cell and animal PD models, CMA and autophagy have not been systemically studied in sporadic PD patients. In the peripheral leukocytes of sporadic PD patients, we examined gene expression levels of lysosome-associated membrane 2 (LAMP-2), a CMA receptor and a limiting step, and microtubule-associated protein 1 light chain 3 (LC3), product of which is sequentially cleaved and lipidated to form LC3-II as an autophagosome marker. Compared to age- and sex-matched healthy controls, LAMP-2 gene expression and protein levels in sporadic PD patients were significantly decreased, which may lead to reduced CMA activity and impaired fusion of autophagosome and lysosome. LC3 gene expression and LC3-II protein levels were significantly increased in sporadic PD patients, suggesting that autophagosomes are accumulated. Our findings, decreased LAMP-2 gene expression and increased LC3 gene expression, are consistent to the previous studies with dopaminergic neuronal cells in vitro and in vivo, which may contribute to the pathogenesis of sporadic PD by altering CMA and autophagy activities. The genetic causes leading to decreased LAMP-2 gene expression need further investigation and genetic or pharmacological restoration of LAMP-2 might be a novel strategy for treating PD patients.

Distinct compartmental distribution of mature and immature dendritic cells in esophageal squamous cell carcinoma

Dendritic cells (DCs) play a critical role in generating anti-tumor immunity. DC functional defect has been related to the growth and progression of various human cancers. In esophageal squamous cell carcinoma (ESCC), the examination of DCs using immunohistochemistry (IHC) with anti-S100 antibody has demonstrated an increased infiltration of DCs into the tumor mass, however, the distribution patterns of DCs at different maturation states in ESCC are not fully evaluated. In this study, we immunohistochemically analyzed the DC maturation status by examining the S100-positive DCs, CD1alpha-positive immature DCs (iDCs), and CD208-positive mature DCs (mDCs) and their distribution patterns in 45 ESCCs and 10 control tissues. The IHC analysis showed that the number of S100-positive DCs was increased in both the cancer epithelium and tumor stroma. Further phenotypic analyses revealed that intraepithelial DCs in the cancer mass were predominantly CD1alpha-positive iDCs. Whereas DCs presented in the tumor stroma were exclusively CD208-positive mDCs, CD208-positive mDCs were particularly dense in the margin of cancerous lesions and formed clusters with CD3-positive lymphocytes. The number of CD208-positive mDCs in the tumor mass was significantly lower than the number of CD1alpha-positive iDCs. The current results suggest that ESCC tissue comprises a high frequency of iDCs in the cancerous epithelium and a low density of mDCs in the tumor stroma. Such a distinct distribution pattern may reflect the ongoing DC tracking in ESCCs.

Autophagy and cell death of Purkinje cells overexpressing Doppel in Ngsk Prnp-deficient mice

In Ngsk prion protein (PrP)-deficient mice (NP(0/0)), ectopic expression of PrP-like protein Doppel (Dpl) in central neurons induces significant Purkinje cell (PC) death resulting in late-onset ataxia. NP(0/0) PC death is partly prevented by either knocking-out the apoptotic factor BAX or overexpressing the anti-apoptotic factor BCL-2 suggesting that apoptosis is involved in Dpl-induced death. In this study, Western blotting and immunohistofluorescence show that both before and during significant PC loss, the scrapie-responsive gene 1 (Scrg1)--potentially associated with autophagy--and the autophagic markers LC3B and p62 increased in the NP(0/0) PCs whereas RT-PCR shows stable mRNA expression, suggesting that the degradation of autophagic products is impaired in NP(0/0) PCs. At the ultrastructural level, autophagic-like profiles accumulated in somatodendritic and axonal compartments of NP(0/0), but not wild-type PCs. The most robust autophagy was observed in NP(0/0) PC axon compartments in the deep cerebellar nuclei suggesting that it is initiated in these axons. Our previous and present data indicate that Dpl triggers autophagy and apoptosis in NP(0/0) PCs. As observed in amyloid neurodegenerative diseases, upregulation of autophagic markers as well as extensive accumulation of autophagosomes in NP(0/0) PCs are likely to reflect a progressive dysfunction of autophagy that could trigger apoptotic cascades.

Distribution of smooth muscle cells and macrophages expressing scavenger receptor BI/II in atherosclerosis

AIM

Scavenger receptors type I and II (SRBI/II) have dual roles in both atherogenic and antiatherogenic functions through interactions with lipoproteins and their expression in macrophages; how-ever, the distribution and density of SRBI/II-positive macrophages and smooth muscle cells (SMCs) as well as their association with lipid metabolism-related proteins in atherosclerotic intima of the human aorta remain unclear.

METHODS

Autopsied aortic tissues were double-immunostained with SRBI/BII and smooth muscle actin or macrophage-specific antibodies. The density of SRBI/BII-positive SMCs and macrophages in intimal lesion was measured. They were also immunostained with antibodies against four apolipoproteins, four phospholipase A2s, and CETP.

RESULTS

SRBI/II was expressed in both macrophages and SMCs distributed in various intimal lesions. The density of SRBI/II-positive SMCs in intimal lesions significantly decreased with the advance of atherosclerosis, whereas the density of SRBI/II-positive macrophages significantly increased with atherosclerotic development. In addition, functional proteins, such as apolipoproteins, secretory phospholipase A2s, and CETP, were distributed in the intimal stroma around SRBI/II-positive cells in all lesion types.

CONCLUSION

The results indicated that SMCs are involved in lipid metabolism via SRBI/II expression mainly in the early stages of atherosclerosis evolution, and that SRBI/II-positive macrophages are mainly involved in advanced stages.

Fluorescence in situ hybridization markers for prediction of cervical lymph node metastases

The presence of lymph node metastases is associated with poor prognosis in early stage cervical cancer. As of yet, no molecular markers predicting lymph node metastases have been identified. We examined single genetic markers and a composite marker, comprised of three fluorescence in situ hybridization (FISH) probes targeting the genes LAMP3, PROX1, and PRKAA1, in pretreatment cervical biopsies from 16 lymph node positive cases and 15 lymph node negative controls from women with stage IB and IIA cervical cancer. In addition, we determined clonal patterns by including CCND1 to compare the clonal constitution of primary tumors and associated lymph node metastases. The composite FISH marker allowed for classification of patients into those with and without lymph node metastases with a sensitivity and specificity of 75% and 87%, respectively (P = 0.001). The positive predictive value and negative predictive value were 86% and 76%, respectively. Clonal patterns varied among the tumors. In many cases, changes between the primary tumor and lymph node metastases in the most common clones may indicate that certain clones have a growth advantage for establishing metastases in lymph nodes. We conclude that the composite FISH marker may be useful for determining risk for subsequent development of lymph node metastases in patients with cervical cancer.

Decreased sputum mature dendritic cells in healthy smokers and patients with chronic obstructive pulmonary disease

BACKGROUND

Asthmatics who smoke have decreased pulmonary mature dendritic cells (DCs). Chronic obstructive pulmonary disease (COPD) patients have an increased amount of pulmonary immature DCs. We hypothesized that healthy smokers and patients with COPD have decreased pulmonary mature DCs.

METHODS

We identified sputum DCs expressing the maturation markers CD83 and DC-lysosome associated membrane protein (DC-LAMP) and DC subpopulations (i.e. myeloid and plasmacytoid DCs) by flow cytometry in healthy smokers before they entered a smoking cessation trial (n = 30), in the same smokers after 6 months of smoking cessation (n = 11) and in COPD patients (n = 28, 14 current and 14 ex-smokers). 12 healthy never-smokers served as controls. DC numbers were expressed as percentage of total sputum CD45(+) leukocytes.

RESULTS

CD83(+) and DC-LAMP(+) mature DCs were decreased in healthy smokers before they ceased smoking compared to after (p = 0.003 and p = 0.049, respectively) and in smokers before smoking cessation compared to never-smokers (p = 0.027 and p = 0.028, respectively). COPD patients, both current and ex-smokers, showed decreased CD83(+) mature DCs compared to never-smokers and smokers after cessation (p = 0.042 and p = 0.004, respectively).

CONCLUSIONS

Cigarette smoking and COPD per se are associated with a decrease in pulmonary mature DCs. We speculate that this reduction is involved in the immunopathogenesis of smoking-related respiratory disorders, such as COPD.

Differential expression of LAMPs and ubiquitin in human thymus

Lysosome-associated membrane proteins 1 and 2 (LAMP-1 and LAMP-2) are implicated in a variety of normal and pathological processes. LAMP-2 is proposed to participate in chaperone-mediated autophagy.Autophagy regulates T-lymphocyte homeostasis by promoting both survival and proliferation. The biological importance of this process in the thymic gland and especially the involvement of LAMPs are far from being elucidated. The aim of the study was to examine the parallel expression of LAMPs and ubiquitin, a key molecule in autophagy, in normal human thymic glands and thymomas. The immunohistochemical expression of both markers was compared with that of cyclin D1--an important regulator of cell cycle progression. Novel evidence for differential expression of LAMPs and ubiquitin is presented. Most Hassal's corpuscules in thymoma were negative for LAMPs, but positive in normal thymus.Both lymphocytes and epithelial cells in pathological thymus showed higher intensity for LAMP-2 compared with LAMP-1. In thymoma, ubiquitin was more intensively positive in these cell types compared with the normal thymus, suggesting activated autophagy in the course of this pathological state. A deregulation in cyclin D1 expression in thymoma is also reported. The functional importance of these molecules in autophagy accompanying normal and pathological processes in the thymic gland is reviewed.

Distinct requirements for activation-induced cell surface expression of preformed Fas/CD95 ligand and cytolytic granule markers in T cells

Fas (CD95/Apo-1) ligand is a potent inducer of apoptosis and one of the major killing effector mechanisms of cytotoxic T cells. Thus, Fas ligand activity has to be tightly regulated, involving various transcriptional and post-transcriptional processes. For example, preformed Fas ligand is stored in secretory lysosomes of activated T cells, and rapidly released by degranulation upon reactivation. In this study, we analyzed the minimal requirements for activation-induced degranulation of Fas ligand. T cell receptor activation can be mimicked by calcium ionophore and phorbol ester. Unexpectedly, we found that stimulation with phorbol ester alone is sufficient to trigger Fas ligand release, whereas calcium ionophore is neither sufficient nor necessary. The relevance of this process was confirmed in primary CD4(+) and CD8(+) T cells and NK cells. Although the activation of protein kinase(s) was absolutely required for Fas ligand degranulation, protein kinase C or A were not involved. Previous reports have shown that preformed Fas ligand co-localizes with other markers of cytolytic granules. We found, however, that the activation-induced degranulation of Fas ligand has distinct requirements and involves different mechanisms than those of the granule markers CD63 and CD107a/Lamp-1. We conclude that activation-induced degranulation of Fas ligand in cytotoxic lymphocytes is differently regulated than other classical cytotoxic granule proteins.

IL-4-induced selective clearance of oligomeric beta-amyloid peptide(1-42) by rat primary type 2 microglia

A hallmark of immunopathology associated with Alzheimer's disease is the presence of activated microglia (MG) surrounding senile plaque deposition of beta-amyloid (Abeta) peptides. Abeta peptides are believed to be potent activators of MG, which leads to Alzheimer's disease pathology, but the role of MG subtypes in Abeta clearance still remains unclear. In this study, we found that IL-4 treatment of rat primary-type 2 MG enhanced uptake and degradation of oligomeric Abeta(1-42) (o-Abeta(1-42)). IL-4 treatment induced significant expression of the scavenger receptor CD36 and the Abeta-degrading enzymes neprilysin (NEP) and insulin-degrading enzyme (IDE) but reduced expression of certain other scavenger receptors. Of cytokines and stimulants tested, the anti-inflammatory cytokines IL-4 and IL-13 effectively enhanced CD36, NEP, and IDE. We demonstrated the CD36 contribution to IL-4-induced Abeta clearance: Chinese hamster ovary cells overexpressing CD36 exhibited marked, dose-dependent degradation of (125)I-labeled o-Abeta(1-42) compared with controls, the degradation being blocked by anti-CD36 Ab. Also, we found IL-4-induced clearance of o-Abeta(1-42) in type 2 MG from CD36-expressing WKY/NCrj rats but not in cells from SHR/NCrj rats with dysfunctional CD36 expression. NEP and IDE also contributed to IL-4-induced degradation of Abeta(1-42), because their inhibitors, thiorphan and insulin, respectively, significantly suppressed this activity. IL-4-stimulated uptake and degradation of o-Abeta(1-42) were selectively enhanced in type 2, but not type 1 MG that express CD40, which suggests that the two MG types may play different neuroimmunomodulating roles in the Abeta-overproducing brain. Thus, selective o-Abeta(1-42) clearance, which is induced by IL-4, may provide an additional focus for developing strategies to prevent and treat Alzheimer's disease.

The effect of LRAP on enamel organ epithelial cell differentiation

Leucine-rich amelogenin peptide (LRAP) is an alternatively spliced amelogenin found in the developing enamel organ. LRAP functions to regulate the development of mesenchymal-derived cells; however, its effect on cells of the enamel organ remains unclear. The hypothesis tested in this study is that LRAP also regulates human enamel organ epithelial cells. Recombinant human LRAP (rH58) was synthesized in E. coli, purified, and exogenously added to cultures of human primary enamel epithelial cells, which were analyzed for changes in cell proliferation and differentiation. rH58 had no effect on cell proliferation, but altered enamel epithelial cell morphology, resulting in larger, more rounded cells. Immunofluorescence showed that rH58 treatment increased amelogenin synthesis, but down-regulated Notch1 expression in enamel epithelial cells. LAMP-1, a membrane receptor for LRAP in mesenchymal cells, was identified and was up-regulated in the presence of rH58. These results suggest that rH58 promotes differentiation of human enamel organ epithelial cells.

Long-term protective effect of mature DC-LAMP+ dendritic cell accumulation in sentinel lymph nodes containing micrometastatic melanoma

PURPOSE

In a previous immunohistochemical study of dendritic cells (DC) in sentinel lymph nodes (SLN) draining regressing melanomas, we found that the accumulation of mature DC-LAMP(+) DCs in SLNs was associated with local expansion of antigen-specific memory effector CTLs and the absence of metastasis in downstream lymph nodes. The aim of this study was to investigate the prognostic importance of the maximal density of mature DCs in SLNs.

EXPERIMENTAL DESIGN

A total of 458 consecutive patients with micrometastatic melanoma within SLNs were eligible for analysis. The maximal density of mature DC-LAMP(+) DCs was evaluated by three independent observers and categorized into three classes (<100, 100 to <200, and >or=200/mm(2)).

RESULTS

There was excellent interobserver reproducibility for maximum density of mature DC-LAMP(+) DC scores (kappa score = 0.82). There were differences in the maximal density scores and staining intensity according to the treating melanoma center (P < 0.001). The higher the mature DC density in the SLN is, the longer is the duration of survival [P = 0.047; hazard ratio, 0.70; 95% confidence interval, 0.50-1.00]. Adjusted by thickness and ulceration, the prognostic importance of DC density was lower (P = 0.36).

CONCLUSION

This study is the first to report the prognostic value of DC-LAMP(+) DC counts in SLNs containing metastatic melanoma. Patients with a high density of mature DCs (>or=200/mm(2)) have the lowest risk of death. It also provides evidence that a lack of maturation in the SLNs is important in biological facilitation of melanoma progression.

Tubulation of class II MHC compartments is microtubule dependent and involves multiple endolysosomal membrane proteins in primary dendritic cells

Immature dendritic cells (DCs) capture exogenous Ags in the periphery for eventual processing in endolysosomes. Upon maturation by TLR agonists, DCs deliver peptide-loaded class II MHC molecules from these compartments to the cell surface via long tubular structures (endolysosomal tubules). The nature and rules that govern the movement of these DC compartments are unknown. In this study, we demonstrate that the tubules contain multiple proteins including the class II MHC molecules and LAMP1, a lysosomal resident protein, as well as CD63 and CD82, members of the tetraspanin family. Endolysosomal tubules can be stained with acidotropic dyes, indicating that they are extensions of lysosomes. However, the proper trafficking of class II MHC molecules themselves is not necessary for endolysosomal tubule formation. DCs lacking MyD88 can also form endolysosomal tubules, demonstrating that MyD88-dependent TLR activation is not necessary for the formation of this compartment. Endolysosomal tubules in DCs exhibit dynamic and saltatory movement, including bidirectional travel. Measured velocities are consistent with motor-based movement along microtubules. Indeed, nocodazole causes the collapse of endolysosomal tubules. In addition to its association with microtubules, endolysosomal tubules follow the plus ends of microtubules as visualized in primary DCs expressing end binding protein 1 (EB1)-enhanced GFP.

Lysosomal membrane-associated glycoproteins are differentially expressed in acute and chronic human thymic involution

The lysosomal membrane-associated glycoproteins LAMP-1 and LAMP-2 are the major constituents of lysosomal membranes with still undefined biological functions. As autophagy is an alternative model of programmed cell death in which lysosomes play a crucial role, we hypothesize that LAMPs might participate in this phenomenon in the involuting thymus. Thymic glands from cases with acute (infection induced) and chronic (senile) involution were examined immunohistochemically for the expression of LAMPs. In acute involution LAMP-1 was localized mainly in medullary epithelial cells, in single macrophages and lymphocytes. Hassall's corpuscules were stained less intensely as compared to control specimens. The quantitative analysis showed a significantly elevated LAMP-2 expression compared to LAMP-1. LAMPs were detected with very slight reactivity in the senile thymus. The enhanced expression of LAMPs, and mainly of LAMP-2, in epithelial cells of incidentally involuted thymus might be an indicator of acute cell injury requiring autophagic degradation of damaged structures. The diminished expression of LAMPs in age-involuted thymus could be a sign of the morphological reorganization and the functional disregulation of the gland. In conclusion, we present novel evidence for differential expression of LAMP-1 and LAMP-2 in thymic involution suggesting their possible involvement in the process of accidental involution of the thymic gland.

Overexpression of LAMP3/TSC403/DC-LAMP promotes metastasis in uterine cervical cancer

LAMP3 (DC-LAMP, TSC403, CD208) was originally isolated as a gene specifically expressed in lung tissues. LAMP3 is located on a chromosome 3q segment that is frequently amplified in some human cancers, including uterine cervical cancer. Because two other members of the LAMP family of lysosomal membrane glycoproteins, LAMP1 and LAMP2, were previously implicated in potentially modulating the interaction of vascular endothelial and cancer cells, we hypothesized that LAMP3 might also play an important part in metastasis. To clarify the metastatic potential of LAMP3 in cervical cancers, we transfected a LAMP3 expression vector into a human uterine cervical cancer cell line, TCS. In an in vitro invasion assay, the migration of LAMP3-overexpressing TCS cells was significantly higher than in control TCS cells. In an in vivo metastasis assay, distant metastasis was detected in 9 of 11 LAMP3-overexpressing TCS cell-injected mice and in only 1 of 11 control mice. Histologic study showed that LAMP3-overexpressing cells readily invaded into the lymph-vascular space. In clinical samples, quantitative real-time reverse transcription-PCR (RT-PCR) analyses showed that LAMP3 mRNA was significantly up-regulated in 47 of 47 (100%) cervical cancers and in 2 of 15 (13%) cervical intraepithelial neoplasias, compared with a low level of LAMP3 mRNA expressed in normal uterine cervixes. Interestingly, high LAMP3 expression was significantly correlated with the overall survival of patients with stage I/II cervical cancers. These findings indicate that LAMP3 overexpression is associated with an enhanced metastatic potential and may be a prognostic factor for cervical cancer.

Role of the endocytic machinery in the sorting of lysosome-associated membrane proteins

The limiting membrane of the lysosome contains a group of transmembrane glycoproteins named lysosome-associated membrane proteins (Lamps). These proteins are targeted to lysosomes by virtue of tyrosine-based sorting signals in their cytosolic tails. Four adaptor protein (AP) complexes, AP-1, AP-2, AP-3, and AP-4, interact with such signals and are therefore candidates for mediating sorting of the Lamps to lysosomes. However, the role of these complexes and of the coat protein, clathrin, in sorting of the Lamps in vivo has either not been addressed or remains controversial. We have used RNA interference to show that AP-2 and clathrin-and to a lesser extent the other AP complexes-are required for efficient delivery of the Lamps to lysosomes. Because AP-2 is exclusively associated with plasma membrane clathrin coats, our observations imply that a significant population of Lamps traffic via the plasma membrane en route to lysosomes.

The apoptosis/autophagy paradox: autophagic vacuolization before apoptotic death

Autophagic cell death is morphologically characterized by an accumulation of autophagic vacuoles. Here, we show that inactivation of LAMP2 by RNA interference or by homologous recombination leads to autophagic vacuolization in nutrient-depleted cells. Cells that lack LAMP2 expression showed an enhanced accumulation of vacuoles carrying the marker LC3, yet a decreased colocalization of LC3 and lysosomes, suggesting that the fusion between autophagic vacuoles and lysosomes was inhibited. While a fraction of mitochondria from starved LAMP2-expressing cells colocalized with lysosomal markers, within autophagolysosomes, no such colocalization was found on removal of LAMP2 from the experimental system. Of note, LAMP1 depletion had no such effects and did not aggravate the phenotype induced by LAMP2-specific small interfering RNA. Serum and amino acid-starved LAMP2-negative cells exhibited an accumulation of autophagic vacuoles and then succumbed to cell death with hallmarks of apoptosis such as loss of the mitochondrial transmembrane potential, caspase activation and chromatin condensation. While caspase inhibition retarded cell death, it had no protective effect on mitochondria. Stabilization of mitochondria by overexpression of Bcl-2 or the mitochondrion-targeted cytomegalovirus protein vMIA, however, blocked all signs of apoptosis. Neither caspase inhibition nor mitochondrial stabilization antagonized autophagic vacuolization in LAMP2-deficient cells. Altogether, these data indicate that accumulation of autophagic vacuoles can precede apoptotic cell death. These findings argue against the clear-cut distinction between type 1 (apoptotic) and type 2 (autophagic) cell death.