Binding of activated alpha2-macroglobulin to its cell surface receptor GRP78 in 1-LN prostate cancer cells regulates PAK-2-dependent activation of LIMK

Blockade of ITGA2/3/5 Promotes Adipogenic Differentiation of Human Adipose-derived Mesenchymal Stem Cells

The integrin α (ITGA) subfamily genes play a fundamental role in various cancers. However, the potential mechanism and application values of ITGA genes in adipogenic differentiation of human adipose-derived stem cells (hADSCs) remain elusive. This study confirmed that ITGA2/3/5 mRNA expressions were repressed during adipogenesis. Blockade of ITGA2/3/5 enhanced adipogenic differentiation of hADSCs. Oil red O staining found that more lipid droplets were apparent in the ITGA2/3/5 inhibition group following 14 d adipogenic induction than in the control group. In addition, inhibition of ITGA2/3/5 promoted the expression of adipogenesis-related genes (PPAR-γ, C/EBPα, FABP4). Mechanistically, ITGA2/3/5 functioned by regulating the Rac1 signaling pathway, which reasonably explains ITGA2/3/5's role in adipogenic differentiation of hADSCs. Our studies suggest that blockades of ITGA2/3/5 promote the adipogenic differentiation of hADSCs.

Role of actin-binding proteins in prostate cancer

The molecular mechanisms driving the onset and metastasis of prostate cancer remain poorly understood. Actin, under the control of actin-binding proteins (ABPs), plays a crucial role in shaping the cellular cytoskeleton, which in turn supports the morphological alterations in normal cells, as well as the invasive spread of tumor cells. Previous research indicates that ABPs of various types serve distinct functions, and any disruptions in their activities could predispose individuals to prostate cancer. These ABPs are intricately implicated in the initiation and advancement of prostate cancer through a complex array of intracellular processes, such as severing, linking, nucleating, inducing branching, assembling, facilitating actin filament elongation, terminating elongation, and promoting actin molecule aggregation. As such, this review synthesizes existing literature on several ABPs linked to prostate cancer, including cofilin, filamin A, and fascin, with the aim of shedding light on the molecular mechanisms through which ABPs influence prostate cancer development and identifying potential therapeutic targets. Ultimately, this comprehensive examination seeks to contribute to the understanding and management of prostate diseases.

PAK2 promotes proliferation, migration, and invasion of lung squamous cell carcinoma through LIMK1/cofilin signaling pathway

Although the p21-activated kinase 2 (PAK2) is an essential serine/threonine protein kinase, its role in lung squamous cell carcinoma (LUSC) progression has yet to be fully understood. We analyzed PAK2 mRNA levels and DNA copy numbers as well as protein levels by quantitative real-time PCR and immunohistochemical staining, respectively, in human LUSC tissues and adjacent normal tissues. Then, we used colony formation assays, cell counting kit-8 assays, matrigel invasion assays, wound healing assays and xenograft models in nude mice to investigate the functions of PAK2 in LUSC progression. We demonstrated that the mRNA levels, DNA copy numbers, and protein levels of PAK2 were up-regulated in human LUSC tissues than in adjacent normal tissues. In addition, a higher PAK2 expression was correlated with a poorer prognosis in LUSC patients. In the in vitro study, we found that PAK2 promoted cell growth, migration, invasion, EMT process, and cell morphology regulation in LUSC cells. Furthermore, PAK2 enhanced tumor cell proliferation, migration, and invasion by regulating actin dynamics through the LIMK1/cofilin signaling. Our findings implicated that the PAK2/LIMK1/cofilin signaling pathway is likely a potential clinical marker and therapeutic target for LUSC.

Predictive Value and Immunological Role of the HSPA5 Gene in Cervical Cancer

Cervical cancer (CC) ranks fourth among women's malignancies worldwide and seriously affects women's health. HSPA5 is a heat shock protein, also known as glucose regulatory protein 78 (GRP78). Upregulation of HSPA5 has been reported to be closely associated with multiple types of tumors. However, the specific role of HSPA5 in cervical cancer has not been discovered. In our study, we explored the prognostic value of HSPA5 in CC. Here, we analyzed the (TCGA) and (UCSC) databases, the analysis of HSPA5 in many tumors types was conducted with the "wilcox. test" method. A False Discovery Rate (FDR) value < 0.05 and Log2 | (fold change, FC) |> 1 were set as the cutoffs. "*", "**", and "***" indicate FDR < 0.05, < 0.01, and < 0.001, respectively, and further used human cervical cancer cells for q-PCR and western blotting detection. q-PCR and western blotting results showed that HSPA5 was highly expressed in cervical cancer cells, while it was expressed at low levels in normal cells (P < 0.05).We also analyzed the immunohistochemical data. immunohistochemical analysis results showed that HSPA5 was highly expressed in human cervical cancer, while it was expressed at low levels in normal tissues (P < 0.05). Analysis in TCGA-UCSC showed that the proportion of G3 in the group with high expression of HSPA5 was relatively high (P < 0.05). Enrichment analysis and survival analysis showed that the increased expression of HSPA5 in cervical cancer was related to the survival of CC and was involved in the regulation of biological behavior and molecular signaling pathways of cervical cancer. The correlation analysis of immune checkpoint and immune infiltration showed that HSPA5 was involved in the regulation of immune process of cervical cancer (P < 0.05). Drug sensitivity correlation analysis showed that HSPA5 was a sensitive target for tumor drugs (P < 0.05). In brief, those results suggest that HSPA5 can act as an oncogene of CC development and can serve as an effective predictive biomarker in cervical cancer.

Cell-Surface GRP78-Targeted Chimeric Antigen Receptor T Cells Eliminate Lung Cancer Tumor Xenografts

Lung cancer is one of the most common and intractable malignancies. It is associated with low survival rates despite existing treatments, indicating that new and more effective therapies are urgently needed such as the chimeric antigen receptor-T (CAR-T) cell immunotherapy. The cell-surface glucose-regulated protein 78 (csGRP78) is expressed in various hematological malignancies and solid tumor cells including lung cancer in response to cancer-related endoplasmic reticulum stress, while GRP78 is restricted to inside the normal cells. Here, we detected the prominent expression of csGRP78 in both lung cancer cell lines, A549 and H1299, as well as cancer stemlike cells derived from A549 by immunofluorescence. Next, a csGRP78-targeted CAR was constructed, and the transduced CAR-T cells were tested for their potency to kill the two lung cancer cell lines and derived stemlike cells, which was correlated with specific interferon γ release in vitro. Finally, we found that csGRP78 CAR-T cells also efficiently killed both lung cancer cells and cancer stemlike cells, resulting into the elimination of tumor xenografts in vivo, neither with any evidence of relapse after 63 days of tumor clearance nor any detrimental impact on other body organs we examined. Our study reveals the capacity of csGRP78 as a therapeutic target and offers valuable insight into the development of csGRP78 CAR-T cells as potential therapy for lung cancer.

Leishmania (L.) amazonensis LaLRR17 increases parasite entry in macrophage by a mechanism dependent on GRP78

Leishmaniases affect 12 million people worldwide. They are caused by Leishmania spp., protozoan parasites transmitted to mammals by female phlebotomine flies. During the life cycle, promastigote forms of the parasite live in the gut of infected sandflies and convert into amastigotes inside the vertebrate macrophages. The parasite evades macrophage's microbicidal responses due to virulence factors that affect parasite phagocytosis, survival and/or proliferation. The interaction between Leishmania and macrophage molecules is essential to phagocytosis and parasite survival. Proteins containing leucine-rich repeats (LRRs) are common in several organisms, and these motifs are usually involved in protein–protein interactions. We have identified the LRR17 gene, which encodes a protein with 6 LRR domains, in the genomes of several Leishmania species. We show here that promastigotes of Leishmania (L.) amazonensis overexpressing LaLRR17 are more infective in vitro. We produced recombinant LaLRR17 protein and identified macrophage 78 kDa glucose-regulated protein (GRP78) as a ligand for LaLRR17 employing affinity chromatography followed by mass spectrometry. We showed that GRP78 binds to LaLRR17 and that its blocking precludes the increase of infection conferred by LaLRR17. Our results are the first to report LRR17 gene and protein, and we hope they stimulate further studies on how this protein increases phagocytosis of Leishmania.

Unveiling the dark side of glucose-regulated protein 78 (GRP78) in cancers and other human pathology: a systematic review

Glucose-Regulated Protein 78 (GRP78) is a chaperone protein that is predominantly expressed in the lumen of the endoplasmic reticulum. GRP78 plays a crucial role in protein folding by assisting in the assembly of misfolded proteins. Under cellular stress conditions, GRP78 can translocate to the cell surface (csGRP78) were it interacts with different ligands to initiate various intracellular pathways. The expression of csGRP78 has been associated with tumor initiation and progression of multiple cancer types. This review provides a comprehensive analysis of the existing evidence on the roles of GRP78 in various types of cancer and other human pathology. Additionally, the review discusses the current understanding of the mechanisms underlying GRP78's involvement in tumorigenesis and cancer advancement. Furthermore, we highlight recent innovative approaches employed in downregulating GRP78 expression in cancers as a potential therapeutic target.

Aberrant LYZ expression in tumor cells serves as the potential biomarker and target for HCC and promotes tumor progression via csGRP78

Hepatocellular carcinoma (HCC) takes the predominant malignancy of hepatocytes with bleak outcomes owing to high heterogeneity among patients. Personalized treatments based on molecular profiles will better improve patients' prognosis. Lysozyme (LYZ), a secretory protein with antibacterial function generally expressed in monocytes/macrophages, has been observed for the prognostic implications in different types of tumors. However, studies about the explicit applicative scenarios and mechanisms for tumor progression are still quite limited, especially for HCC. Here, based on the proteomic molecular classification data of early-stage HCC, we revealed that the LYZ level was elevated significantly in the most malignant HCC subtype and could serve as an independent prognostic predictor for HCC patients. Molecular profiles of LYZ-high HCCs were typical of those for the most malignant HCC subtype, with impaired metabolism, along with promoted proliferation and metastasis characteristics. Further studies demonstrated that LYZ tended to be aberrantly expressed in poorly differentiated HCC cells, which was regulated by STAT3 activation. LYZ promoted HCC proliferation and migration in both autocrine and paracrine manners independent of the muramidase activity through the activation of downstream protumoral signaling pathways via cell surface GRP78. Subcutaneous and orthotopic xenograft tumor models indicated that targeting LYZ inhibited HCC growth markedly in NOD/SCID mice. These results propose LYZ as a prognostic biomarker and therapeutic target for the subclass of HCC with an aggressive phenotype.

Targeting P21-Activated Kinase-1 for Metastatic Prostate Cancer

Metastatic prostate cancer (mPCa) has limited therapeutic options and a high mortality rate. The p21-activated kinase (PAK) family of proteins is important in cell survival, proliferation, and motility in physiology, and pathologies such as infectious, inflammatory, vascular, and neurological diseases as well as cancers. Group-I PAKs (PAK1, PAK2, and PAK3) are involved in the regulation of actin dynamics and thus are integral for cell morphology, adhesion to the extracellular matrix, and cell motility. They also play prominent roles in cell survival and proliferation. These properties make group-I PAKs a potentially important target for cancer therapy. In contrast to normal prostate and prostatic epithelial cells, group-I PAKs are highly expressed in mPCA and PCa tissue. Importantly, the expression of group-I PAKs is proportional to the Gleason score of the patients. While several compounds have been identified that target group-I PAKs and these are active in cells and mice, and while some inhibitors have entered human trials, as of yet, none have been FDA-approved. Probable reasons for this lack of translation include issues related to selectivity, specificity, stability, and efficacy resulting in side effects and/or lack of efficacy. In the current review, we describe the pathophysiology and current treatment guidelines of PCa, present group-I PAKs as a potential druggable target to treat mPCa patients, and discuss the various ATP-competitive and allosteric inhibitors of PAKs. We also discuss the development and testing of a nanotechnology-based therapeutic formulation of group-I PAK inhibitors and its significant potential advantages as a novel, selective, stable, and efficacious mPCa therapeutic over other PCa therapeutics in the pipeline.

Cisplatin Induces Senescent Lung Cancer Cell-Mediated Stemness Induction via GRP78/Akt-Dependent Mechanism

Cellular senescence is linked with chemotherapy resistance. Based on previous studies, GRP78 is a signal transducer in senescent cells. However, the association between GRP78 and stem cell phenotype remains unknown. Cisplatin treatment was clarified to induce cellular senescence leading to stemness induction via GRP78/Akt signal transduction. H460 cells were treated with 5 μM of cisplatin for 6 days to develop senescence. The colony formation assay and cell cycle analysis were performed. SA-β-galactosidase staining indicated senescence. Western blot analysis and RT-PCR were operated. Immunoprecipitation (IP) and immunocytochemistry assays (ICC) were also performed. Colony-forming activity was completely inhibited, and 87.07% of the cell population was arrested in the G2 phase of the cell cycle. mRNA of p21 and p53 increased approximately by 15.91- and 19.32-fold, respectively. The protein level of p21 and p53 was elevated by 9.57- and 5.9-fold, respectively. In addition, the c-Myc protein level was decreased by 0.2-fold when compared with the non-treatment control. Even though, the total of GRP78 protein was downregulated after cisplatin treatment, but the MTJ1 and downstream regulator, p-Akt/Akt ratio were upregulated by approximately 3.38 and 1.44-fold, respectively. GRP78 and MTJ1 were found at the cell surface membrane. Results showed that the GRP78/MTJ1 complex and stemness markers, including CD44, CD133, Nanog, Oct4, and Sox2, were concomitantly increased in senescent cells. MTJ1 anchored GRP78, facilitating the signal transduction of stem-like phenotypes. The strategy that could interrupt the binding between these crucial proteins or inhibit the translocation of GRP78 might beuseful for cancer therapy.

GRP78 plays a key role in sperm function via the PI3K/PDK1/AKT pathway

Glucose-regulated protein 78 (GRP78), which is commonly found in the endoplasmic reticulum (ER), is involved in stabilizing ER proteins and inducing the unfolded protein response. Furthermore, GRP78 is expressed on the surface of most common cancer cells, such as cells of breast, lung, liver, and prostate cancers, and plays a role in apoptosis and cell proliferation via the PI3K/PDK1/AKT signaling pathway. Therefore, various trials have been performed for evaluating cancer treatment by inhibiting GRP78. Moreover, GRP78 is expressed on the surface of spermatozoa; however, its role in spermatozoa physiology remains unclear. Therefore, this study was designed to investigate the effects of GRP78 on sperm function during capacitation and elucidate the underlying mechanisms. Boar spermatozoa were exposed to various concentrations of HA15, a GRP78 antagonist, and sperm kinematic parameters, capacitation status, cell viability, levels of PI3K/PDK1/AKT-pathway related proteins, and tyrosine phosphorylation were evaluated. GRP78 inhibition significantly decreased sperm motility, kinematic parameters, capacitated and acrosome-reacted spermatozoa counts, and cell viability. Moreover, GRP78 expression was significantly decreased in HA15-treated spermatozoa compared to that in the control group, and levels of PI3K/PDK1/AKT-pathway related proteins changed significantly. Furthermore, tyrosine phosphorylation was significantly altered in the HA15-treated group. The results of this study suggest that GRP78 inhibition in cancer therapy may negatively affect sperm function. These results lay a strong foundation for future studies aiming to identify the molecular mechanisms related to GRP78 in spermatozoa.

Ultrasensitive Detection of GRP78 in Exosomes and Observation of Migration and Proliferation of Cancer Cells by Application of GRP78-Containing Exosomes

Simple Summary

Cancer cells release exosomes to their surrounding cells, and it is believed that trace amounts of proteins included in exosomes promote cancer stemness. In the present study, we note 78-kDa glucose-regulated protein (GRP78), which is involved in cancer progression, and present the protocol for measurements of trace amounts of GRP78 in exosomes released from cultured gastric cancer cells using an ultrasensitive ELISA with thio-NAD cycling. We found that when high-GRP78-containing exosomes were incubated with cultured cancer cells, these cells increased their stemness, for example, an increase in indices of both an MTT assay and a wound healing assay. The technique for quantifying proteins in exosomes described here will advance our understanding of cancer stemness progression via exosomes.

Abstract

Cancer cells communicate with each other via exosomes in the tumor microenvironment. However, measuring trace amounts of proteins in exosomes is difficult, and thus the cancer stemness-promoting mechanisms of exosomal proteins have not been elucidated. In the present study, we attempted to quantify trace amounts of 78-kDa glucose-regulated protein (GRP78), which is involved in cancer progression, in exosomes released from cultured gastric cancer cells using an ultrasensitive ELISA combined with thio-NAD cycling. We also evaluated the cancer stemness-promoting effects by the application of high-GRP78-containing exosomes to cultured gastric cancer cells. The ultrasensitive ELISA enabled the detection of GRP78 at a limit of detection of 0.16 pg/mL. The stemness of cancer cultured cells incubated with high-GRP78-containing exosomes obtained from GRP78-overexpressed cells was increased on the basis of both an MTT assay and a wound healing assay. Our results demonstrated that the ultrasensitive ELISA has strong potential to measure trace amounts of proteins in exosomes. Further, exosomes with a high concentration of GRP78 promote the cancer stemness of surrounding cells. The technique for quantifying proteins in exosomes described here will advance our understanding of cancer stemness progression via exosomes.

Potential to Eradicate Cancer Stemness by Targeting Cell Surface GRP78

Cancer stemness is proposed to be the main cause of metastasis and tumor relapse after conventional therapy due to the main properties of cancer stem cells. These include unlimited self-renewal, the low percentage in a cell population, asymmetric/symmetric cell division, and the hypothetical different nature for absorbing external substances. As the mechanism of how cancer stemness is maintained remains unknown, further investigation into the basic features of cancer stemness is required. Many articles demonstrated that glucose-regulated protein 78 (GRP78) plays a key role in cancer stemness, suggesting that this molecule is feasible for targeting cancer stem cells. This review summarizes the history of finding cancer stem cells, as well as the functions of GRP78 in cancer stemness, for discussing the possibility of targeting GRP78 to eradicate cancer stemness.

The Chaperone Protein GRP78 Promotes Survival and Migration of Head and Neck Cancer After Direct Radiation Exposure and Extracellular Vesicle-Transfer

Background and Purpose

Increased levels of the chaperone protein GRP78 have been implicated in poorer outcomes of cancer therapy. We have therefore explored the functional connection between the expression of GRP78 and the development of radioresistance and metastatic behavior in HNSCC.

Material and Methods

The association between gene expression of GRP78 and survival in HNSCC patients was examined using the TCGA database. The influence of ionizing radiation on the GRP78 levels in HNSCC cell lines, their secreted extracellular vesicles (EV) and non-irradiated EV-recipient cells was investigated by Western Blot and FACS. The consequences of chemical inhibition or experimental overexpression of GRP78 on radioresistance and migration of HNSCC cells were analyzed by clonogenic survival and gap closure assays.

Results

Elevated levels of GRP78 RNA in HNSCC correlated with poorer overall survival. Radiation increased GRP78 protein expression on the surface of HNSCC cell lines. Experimental overexpression of GRP78 increased both radioresistance and migratory potential. Chemical inhibition of GRP78 impaired cell migration. EVs were identified as a potential source of increased GRP78 content as elevated levels of surface GRP78 were found in EVs released by irradiated cells. These vesicles transferred GRP78 to non-irradiated recipient cells during co-cultivation.

Conclusions

We have identified the chaperone protein GRP78 as a potential driver of increased radioresistance and motility in HNSCC. The uptake of GRP78-rich EVs originating from irradiated cells may contribute to a poorer prognosis through bystander effects mediated by the transfer of GRP78 to non-irradiated cells. Therefore, we consider the chaperone protein GRP78 to be an attractive target for improving radiotherapy strategies.

LIM Kinases in Osteosarcoma Development

Tumorigenesis is a long-term and multistage process that often leads to the formation of metastases. During this pathological course, two major events appear to be crucial: primary tumour growth and metastatic expansion. In this context, despite research and clinical advances during the past decades, bone cancers remain a leading cause of death worldwide among paediatric cancer patients. Osteosarcomas are the most common malignant bone tumours in children and adolescents. Notwithstanding advances in therapeutic treatments, many patients succumb to these diseases. In particular, less than 30% of patients who demonstrate metastases at diagnosis or are poor responders to chemotherapy survive 5 years after initial diagnosis. LIM kinases (LIMKs), comprising LIMK1 and LIMK2, are common downstream effectors of several signalization pathways, and function as a signalling node that controls cytoskeleton dynamics through the phosphorylation of the cofilin family proteins. In recent decades, several reports have indicated that the functions of LIMKs are mainly implicated in the regulation of actin microfilament and the control of microtubule dynamics. Previous studies have thus identified LIMKs as cancer-promoting regulators in multiple organ cancers, such as breast cancer or prostate cancer. This review updates the current understanding of LIMK involvement in osteosarcoma progression.

Hepatokine Pregnancy Zone Protein Governs the Diet-Induced Thermogenesis Through Activating Brown Adipose Tissue

Intermittent fasting (IF), as a dietary intervention for weight loss, takes effects primarily through increasing energy expenditure. However, whether inter-organ systems play a key role in IF remains unclear. Here, a novel hepatokine, pregnancy zone protein (PZP) is identified, which has significant induction during the refeeding stage of IF. Further, loss of function studies and protein therapeutic experiment in mice revealed that PZP promotes diet-induced thermogenesis through activating brown adipose tissue (BAT). Mechanistically, circulating PZP can bind to cell surface glucose-regulated protein of 78 kDa (GRP78) to promote uncoupling protein 1 (UCP1) expression via a p38 MAPK-ATF2 signaling pathway in BAT. These studies illuminate a systemic regulation in which the IF promotes BAT thermogenesis through the endocrinal system and provide a novel potential target for treating obesity and related disorders.

Glucose-regulated protein (GRP78) is an important cell surface receptor for viral invasion, cancers, and neurological disorders

The 78 kDa glucose-regulated protein (GRP78) is an endoplasmic reticulum (ER)-resident molecular chaperone. GRP78 is a member of the 70 kDa heat shock family of proteins involved in correcting and clearing misfolded proteins in the ER. In response to cellular stress, GRP78 escapes from the ER and moves to the plasma membrane where it (a) functions as a receptor for many ligands, and (b) behaves as an autoantigen for autoantibodies that contribute to human disease and cancer. Cell surface GRP78 (csGRP78) associates with the major histocompatibility complex class I (MHC-I), and is the port of entry for several viruses, including the predictive binding of the novel SARS-CoV-2. Furthermore, csGRP78 is found in association with partners as diverse as the teratocarcinoma-derived growth factor 1 (Cripto), the melanocortin-4 receptor (MC4R) and the DnaJ-like protein MTJ-1. CsGRP78 also serves as a receptor for a large variety of ligands including activated α₂ -macroglobulin (α₂ M*), plasminogen kringle 5 (K5), microplasminogen, the voltage-dependent anion channel (VDAC), tissue factor (TF), and the prostate apoptosis response-4 protein (Par-4). In this review, we discuss the mechanisms involved in the translocation of GRP78 from the ER to the cell surface, and the role of secreted GRP78 and its autoantibodies in cancer and neurological disorders.

CD9, a potential leukemia stem cell marker, regulates drug resistance and leukemia development in acute myeloid leukemia

BACKGROUND

Leukemia stem cells (LSCs) are responsible for the initiation, progression, and relapse of acute myeloid leukemia (AML). Therefore, a therapeutic strategy targeting LSCs is a potential approach to eradicate AML. In this study, we aimed to identify LSC-specific surface markers and uncover the underlying mechanism of AML LSCs.

METHODS

Microarray gene expression data were used to investigate candidate AML-LSC-specific markers. CD9 expression in AML cell lines, patients with AML, and normal donors was evaluated by flow cytometry (FC). The biological characteristics of CD9-positive (CD9⁺) cells were analyzed by in vitro proliferation, chemotherapeutic drug resistance, migration, and in vivo xenotransplantation assays. The molecular mechanism involved in CD9⁺ cell function was investigated by gene expression profiling. The effects of alpha-2-macroglobulin (A2M) on CD9⁺ cells were analyzed with regard to proliferation, drug resistance, and migration.

RESULTS

CD9, a cell surface protein, was specifically expressed on AML LSCs but barely detected on normal hematopoietic stem cells (HSCs). CD9⁺ cells exhibit more resistance to chemotherapy drugs and higher migration potential than do CD9-negative (CD9^-) cells. More importantly, CD9⁺ cells possess the ability to reconstitute human AML in immunocompromised mice and promote leukemia growth, suggesting that CD9⁺ cells define the LSC population. Furthermore, we identified that A2M plays a crucial role in maintaining CD9⁺ LSC stemness. Knockdown of A2M impairs drug resistance and migration of CD9⁺ cells.

CONCLUSION

Our findings suggest that CD9 is a new biomarker of AML LSCs and is a promising therapeutic target.

Cell surface GRP78 regulates BACE2 via lysosome-dependent manner to maintain mesenchymal phenotype of glioma stem cells

BACKGROUND

Glioma stem cells (GSCs) are considered the initial cells of gliomas, contributing to therapeutic resistance. Patient-derived GSCs well recapitulate the heterogeneity of their parent glioma tissues, which can be classified into different subtypes. Likewise, previous works identified GSCs as two distinct subtypes, mesenchymal (MES) and proneural (PN) subtypes, and with general recognition, the MES subtype is considered a more malignant phenotype characterized by high invasion and radioresistance. Therefore, understanding the mechanisms involved in the MES phenotype is necessary for glioblastoma treatment.

METHODS

Data for bioinformatic analysis were obtained from The Cancer Genome Atlas (TCGA) and The Gene Expression Omnibus (GEO) database. An antibody was used to block cell surface glucose-regulated protein 78 (csGRP78). Apoptosis and cell cycle analyses were performed to evaluate radiation damage. Immunofluorescence staining was applied to assess protein expression and distribution. Mass spectrometry combined with bioinformatic analysis was used to screen downstream molecules. Intracranial GSC-derived xenografts were established for in vivo experiments.

RESULTS

Total GRP78 expression was associated with MES GSC stemness, and csGRP78 was highly expressed in MES GSCs. Targeting csGRP78 suppressed the self-renewal and radioresistance of MES GSCs in vitro and in vivo, accompanied by downregulation of the STAT3, NF-κB and C/EBPβ pathways. Mass spectrometry revealed the potential downstream β-site APP-cleaving enzyme 2 (BACE2), which was regulated by csGRP78 via lysosomal degradation. Knockdown of BACE2 inactivated NF-κB and C/EBPβ and significantly suppressed the tumorigenesis and radioresistance of MES GSCs in vitro and in vivo.

CONCLUSIONS

Cell surface GRP78 was preferentially expressed in MES GSCs and played a pivotal role in MES phenotype maintenance. Thus, blocking csGRP78 in MES GSCs with a high-specificity antibody might be a promising novel therapeutic strategy.

Characterizing Cell Stress and GRP78 in Glioma to Enhance Tumor Treatment

Glioblastoma (GBM) is the most common primary brain tumor, carrying a very poor prognosis, with median overall survival at about 12 to 15 months despite surgical resection, chemotherapy with temozolomide (TMZ), and radiation therapy. GBM recurs in the vast majority of patients, with recurrent tumors commonly displaying increase in resistance to standard of care chemotherapy, TMZ, as well as radiotherapy. One of the most commonly cited mechanisms of chemotherapeutic and radio-resistance occurs via the glucose-regulated protein 78 (GRP78), a well-studied mediator of the unfolded protein response (UPR), that has also demonstrated potential as a biomarker in GBM. Overexpression of GRP78 has been directly correlated with malignant tumor characteristics, including higher tumor grade, cellular proliferation, migration, invasion, poorer responses to TMZ and radiation therapy, and poorer patient outcomes. GRP78 expression is also higher in GBM tumor cells upon recurrence. Meanwhile, knockdown or suppression of GRP78 has been shown to sensitize cells to TMZ and radiation therapy. In light of these findings, various novel developing therapies are targeting GRP78 as monotherapies, combination therapies that enhance the effects of TMZ and radiation therapy, and as treatment delivery modalities. In this review, we delineate the mechanisms by which GRP78 has been noted to specifically modulate glioblastoma behavior and discuss current developing therapies involving GRP78 in GBM. While further research is necessary to translate these developing therapies into clinical settings, GRP78-based therapies hold promise in improving current standard-of-care GBM therapy and may ultimately lead to improved patient outcomes.

Glucose-regulated protein 78 (GRP78) as a potential novel biomarker and therapeutic target in multiple myeloma

INTRODUCTION

Glucose-regulated protein 78 (GRP78) is a stress-inducible molecular chaperone expressed within the endoplasmic reticulum where it acts as a master regulator of the unfolded protein response (UPR) pathway. At times of ER stress, activation of the UPR, a multimolecular pathway, limits proteotoxicity induced by misfolded proteins. In malignancies, including multiple myeloma which is characterized by an accumulation of misfolded immunoglobulins, GRP78 expression is increased, with notable translocation of GRP78 to the cell surface. Studies suggest cell-surface GRP78 (csGRP78) to be of prognostic significance with emerging evidence that it interacts with a myriad of co-ligands to activate signaling pathways promoting cell proliferation and survival or apoptosis.

AREAS COVERED

This review focuses on the role of ER and csGRP78 in physiology and oncogenesis in multiple myeloma, addressing factors that shift the balance in GRP78 signaling from survival to apoptosis. The role of GRP78 as a potential prognostic biomarker is explored and current therapeutics in development aimed at targeting csGRP78 are addressed. We conducted a PubMed literature search using the keywords 'GRP78,' 'multiple myeloma' reviewing studies prior to 2020.

EXPERT OPINION

Cell-surface GRP78 expression is a potential novel prognostic biomarker in myeloma and targeting of csGRP78 is promising and requires further investigation.

Cell surface GRP78 promotes stemness in normal and neoplastic cells

Reliable approaches to identify stem cell mechanisms that mediate aggressive cancer could have great therapeutic value, based on the growing evidence of embryonic signatures in metastatic cancers. However, how to best identify and target stem-like mechanisms aberrantly acquired by cancer cells has been challenging. We harnessed the power of reprogramming to examine GRP78, a chaperone protein generally restricted to the endoplasmic reticulum in normal tissues, but which is expressed on the cell surface of human embryonic stem cells and many cancer types. We have discovered that (1) cell surface GRP78 (sGRP78) is expressed on iPSCs and is important in reprogramming, (2) sGRP78 promotes cellular functions in both pluripotent and breast cancer cells (3) overexpression of GRP78 in breast cancer cells leads to an induction of a CD24⁻/CD44⁺ tumor initiating cell (TIC) population (4) sGRP78⁺ breast cancer cells are enriched for stemness genes and appear to be a subset of TICs (5) sGRP78⁺ breast cancer cells show an enhanced ability to seed metastatic organ sites in vivo. These collective findings show that GRP78 has important functions in regulating both pluripotency and oncogenesis, and suggest that sGRP78 marks a stem-like population in breast cancer cells that has increased metastatic potential in vivo.

Development of novel therapeutics for the treatment of glaucoma based on actin-binding kinase inhibition – in silico approach

QSAR modeling with computer-aided drug design were used for the in silico development of novel therapeutics for glaucoma treatment.

microRNAs in Cardiovascular Disease: Small Molecules but Big Roles

microRNAs (miRNAs) are an evolutionarily conserved class of small single-stranded noncoding RNAs. The aberrant expression of specific miRNAs has been implicated in the development and progression of diverse cardiovascular diseases. For many decades, miRNA therapeutics has flourished, taking advantage of the fact that miRNAs can modulate gene expression and control cellular phenotypes at the posttranscriptional level. Genetic replacement or knockdown of target miRNAs by chemical molecules, referred to as miRNA mimics or inhibitors, has been used to reverse their abnormal expression as well as their adverse biological effects in vitro and in vivo in an effort to fully implement the therapeutic potential of miRNA-targeting treatment. However, the limitations of the chemical structure and delivery systems are hindering progress towards clinical translation. Here, we focus on the regulatory mechanisms and therapeutic trials of several representative miRNAs in the context of specific cardiovascular diseases; from this basic perspective, we evaluate chemical modifications and delivery vectors of miRNA-based chemical molecules and consider the underlying challenges of miRNA therapeutics as well as the clinical perspectives on their applications.

GRP78 regulates CD44v membrane homeostasis and cell spreading in tamoxifen-resistant breast cancer

GRP78 conducts protein folding and quality control in the ER and shows elevated expression and cell surface translocation in advanced tumors. However, the underlying mechanisms enabling GRP78 to exert novel signaling functions at cell surface are just emerging. CD44 is a transmembrane protein and an important regulator of cancer metastasis, and isoform switch of CD44 through incorporating additional variable exons to the extracellular juxtamembrane region is frequently observed during cancer progression. Using super-resolution dual-color single-particle tracking, we report that GRP78 interacts with CD44v in plasma membrane nanodomains of breast cancer cells. We further show that targeting cell surface GRP78 by the antibodies can effectively reduce cell surface expression of CD44v and cell spreading of tamoxifen-resistant breast cancer cells. Our results uncover new functions of GRP78 as an interacting partner of CD44v and as a regulator of CD44v membrane homeostasis and cell spreading. This study also provides new insights into anti-CD44 therapy in tamoxifen-resistant breast cancer.

Targeting cell surface GRP78 enhances pancreatic cancer radiosensitivity through YAP/TAZ protein signaling

Ionizing radiation (IR) can promote migration and invasion of cancer cells, but the basis for this phenomenon has not been fully elucidated. IR increases expression of glucose-regulated protein 78kDa (GRP78) on the surface of cancer cells (CS-GRP78), and this up-regulation is associated with more aggressive behavior, radioresistance, and recurrence of cancer. Here, using various biochemical and immunological methods, including flow cytometry, cell proliferation and migration assays, Rho activation and quantitative RT-PCR assays, we investigated the mechanism by which CS-GRP78 contributes to radioresistance in pancreatic ductal adenocarcinoma (PDAC) cells. We found that activated α₂-Macroglobulin (α₂M*) a ligand of the CS-GRP78 receptor, induces formation of the AKT kinase (AKT)/DLC1 Rho-GTPase-activating protein (DLC1) complex and thereby increases Rho activation. Further, CS-GRP78 activated the transcriptional coactivators Yes-associated protein (YAP) and tafazzin (TAZ) in a Rho-dependent manner, promoting motility and invasiveness of PDAC cells. We observed that radiation-induced CS-GRP78 stimulates the nuclear accumulation of YAP/TAZ and increases YAP/TAZ target gene expressions. Remarkably, targeting CS-GRP78 with C38 monoclonal antibody (Mab) enhanced radiosensitivity and increased the efficacy of radiation therapy by curtailing PDAC cell motility and invasion. These findings reveal that CS-GRP78 acts upstream of YAP/TAZ signaling and promote migration and radiation-resistance in PDAC cells. We therefore conclude that, C38 Mab is a promising candidate for use in combination with radiation therapy to manage PDAC.

Urinary exosome miR-30c-5p as a biomarker of clear cell renal cell carcinoma that inhibits progression by targeting HSPA5

Exosome-derived miRNAs are regarded as biomarkers for the diagnosis and prognosis of many human cancers. However, its function in clear cell renal cell carcinoma (ccRCC) remains unclear. In this study, differentially expressed miRNAs from urinal exosomes were identified using next-generation sequencing (NGS) and verified using urine samples of ccRCC patients and healthy donors. Then, the exosomes were analysed in early-stage ccRCC patients, healthy individuals and patients suffering from other urinary system cancers. Thereafter, the target gene of the miRNA was detected. Its biological function was investigated in vitro and in vivo. The results showed that miR-30c-5p could be amplified in a stable manner. Its expression pattern was significantly different only between ccRCC patients and healthy control individuals, but not compared with that of other urinary system cancers, which indicated its specificity for ccRCC. Additionally, the overexpression of miR-30c-5p inhibited ccRCC progression in vitro and in vivo. Heat-shock protein 5 (HSPA5) was found to be a direct target gene of miR-30c-5p. The depletion of HSPA5 caused by miR-30c-5p inhibition reversed the promoting effect of ccRCC growth. In conclusion, urinary exosomal miR-30c-5p acts as a potential diagnostic biomarker of early-stage ccRCC and may be able to modulate the expression of HSPA5, which is correlated with the progression of ccRCC.

Chemotherapy Resistance Explained through Endoplasmic Reticulum Stress-Dependent Signaling

Cancers cells have the ability to develop chemotherapy resistance, which is a persistent problem during cancer treatment. Chemotherapy resistance develops through different molecular mechanisms, which lead to modification of the cancer cells signals needed for cellular proliferation or for stimulating an immune response. The endoplasmic reticulum (ER) is an important organelle involved in protein quality control, by promoting the correct folding of protein and ER-mediated degradation of unfolded or misfolded protein, namely, ER-associated degradation. Disturbances of the normal ER functions causes an accumulation of unfolded or misfolded proteins in the ER lumen, resulting in a condition called “ER stress (ERS).” ERS triggers the unfolded protein response (UPR)—also called the ERS response (ERSR)—to restore homeostasis or activate cell death. Although the ERSR is one emerging potential target for chemotherapeutics to treat cancer, it is also critical for chemotherapeutics resistance, as well. However, the detailed molecular mechanism of the relationship between the ERSR and tumor survival or drug resistance remains to be fully understood. In this review, we aim to describe the most vital molecular mechanism of the relationship between the ERSR and chemotherapy resistance. Moreover, the review also discusses the molecular mechanism of ER stress-mediated apoptosis on cancer treatments.

Unfolded Protein Response as a Therapeutic Target in Cardiovascular Disease

Cardiovascular disease is the leading cause of death worldwide. Despite overwhelming socioeconomic impact and mounting clinical needs, our understanding of the underlying pathophysiology remains incomplete. Multiple forms of cardiovascular disease involve an acute or chronic disturbance in cardiac myocytes, which may lead to potent activation of the Unfolded Protein Response (UPR), a cellular adaptive reaction to accommodate protein-folding stress. Accumulation of unfolded or misfolded proteins in the Endoplasmic Reticulum (ER) elicits three signaling branches of the UPR, which otherwise remain quiescent. This ER stress response then transiently suppresses global protein translation, augments production of protein-folding chaperones, and enhances ER-associated protein degradation, with an aim to restore cellular homeostasis. Ample evidence has established that the UPR is strongly induced in heart disease. Recently, the mechanisms of action and multiple pharmacological means to favorably modulate the UPR are emerging to curb the initiation and progression of cardiovascular disease. Here, we review the current understanding of the UPR in cardiovascular disease and discuss existing therapeutic explorations and future directions.

Anti-GRP78 autoantibodies induce endothelial cell activation and accelerate the development of atherosclerotic lesions

The 78-kDa glucose-regulated protein (GRP78) is an ER molecular chaperone that aids in protein folding and secretion. However, pathological conditions that cause ER stress can promote the relocalization of GRP78 to the cell surface (csGRP78), where it acts as a signaling receptor to promote cancer progression. csGRP78 also possesses antigenic properties, leading to the production of anti-GRP78 autoantibodies, which contribute to tumor growth. In contrast, the presence and role of anti-GRP78 autoantibodies in atherosclerosis is unknown. Here, we show that atherosclerotic-prone ApoE-/- mice develop circulating anti-GRP78 autoantibodies that bind to csGRP78 on lesion-resident endothelial cells. Moreover, GRP78-immunized ApoE-/- mice exhibit a marked increase in circulating anti-GRP78 autoantibody titers that correlated with accelerated lesion growth. Mechanistically, engagement of anti-GRP78 autoantibodies with csGRP78 on human endothelial cells activated NF-κB, thereby inducing the expression of ICAM-1 and VCAM-1, a process blocked by NF-κB inhibitors. Disrupting the autoantibody/csGRP78 complex with enoxaparin, a low-molecular-weight heparin, reduced the expression of adhesion molecules and attenuated lesion growth. In conclusion, anti-GRP78 autoantibodies play a crucial role in atherosclerosis development, and disruption of the interaction between anti-GRP78 autoantibodies and csGRP78 represents a therapeutic strategy.

Interleukin 34 (IL-34) cell-surface localization regulated by the molecular chaperone 78-kDa glucose-regulated protein facilitates the differentiation of monocytic cells

Interleukin 34 (IL-34) constitutes a cytokine that shares a common receptor, colony-stimulating factor-1 receptor (CSF-1R), with CSF-1. We recently identified a novel type of monocytic cell termed follicular dendritic cell-induced monocytic cells (FDMCs), whose differentiation depended on CSF-1R signaling through the IL-34 produced from a follicular dendritic cell line, FL-Y. Here, we report the functional mechanisms of the IL-34-mediated CSF-1R signaling underlying FDMC differentiation. CRIPSR/Cas9-mediated knockout of the Il34 gene confirmed that the ability of FL-Y cells to induce FDMCs completely depends on the IL-34 expressed by FL-Y cells. Transwell culture experiments revealed that FDMC differentiation requires a signal from a membrane-anchored form of IL-34 on the FL-Y cell surface, but not from a secreted form, in a direct interaction between FDMC precursor cells and FL-Y cells. Furthermore, flow cytometric analysis using an anti-IL-34 antibody indicated that IL-34 was also expressed on the FL-Y cell surface. Thus, we explored proteins interacting with IL-34 in FL-Y cells. Mass spectrometry analysis and pulldown assay identified that IL-34 was associated with the molecular chaperone 78-kDa glucose-regulated protein (GRP78) in the plasma membrane fraction of FL-Y cells. Consistent with this finding, GRP78-heterozygous FL-Y cells expressed a lower level of IL-34 protein on their cell surface and exhibited a reduced competency to induce FDMC differentiation compared with the original FL-Y cells. These results indicated a novel GRP78-dependent localization and specific function of IL-34 in FL-Y cells related to monocytic cell differentiation.

GRP75 modulates oncogenic Dbl-driven endocytosis derailed via the CHIP-mediated ubiquitin degradation pathway

Chaperone-assisted proteasome degradation of oncogenic protein acts as an upstream signal controlling tumorigenesis and progression. The understanding of the co-regulation of chaperone and oncoprotein of endocytosis pathways is extremely limited. In this study, we showed for the first time that proto-Dbl (dbl proto-oncogene product) is co-enriched with mitochondrial chaperone GRP75 in endocytosis vesicles from ovarian cancer cells. onco-Dbl, produced by oncogenic mutation/degradation of proto-Dbl, markedly enhanced cellular macropinocytosis but suppressed clathrin-mediated endocytosis and clathrin-independent endocytosis pathways, presenting a derailed endocytosis phenotype. GRP75 was associated with proto-Dbl inside cells and modulated Dbl-driven endocytosis derailed by a co-regulatory mode. In spite of not being a component of the Hsc70/Hsp90/proto-Dbl complex, the degradation of proto-Dbl was promoted by GRP75 through the CHIP-mediated ubiquitin–proteasome pathway, of which GRP75 acts as a cooperator with CHIP but also acts as a competitor to Hsc70 and Hsp90 in the multiple chaperones-assisted pro-folding/pro-degradation machinery. Knockdown or inhibition of GRP75 attenuated proto-Dbl degradation and reduced the onco-Dbl level, which differentially impaired Rho GTPases activation and therefore shifted the endocytosis-derailed phenotype. Our data uncovered a novel GRP75-Dbl endocytosis regulatory axis and provided an alternative using chaperone inhibitor to shut down the oncoprotein-driven endocytosis derailment mechanism.

PSA-alpha-2-macroglobulin complex is enzymatically active in the serum of patients with advanced prostate cancer and can degrade circulating peptide hormones

BACKGROUND

Prostate cancer cells produce high levels of the serine protease Prostate-Specific Antigen (PSA). PSA is enzymatically active in the tumor microenvironment but is presumed to be enzymatically inactive in the blood due to complex formation with serum protease inhibitors α-1-antichymotrypsin and α-2-macroglobulin (A2M). PSA-A2M complexes cannot be measured by standard ELISA assays and are also rapidly cleared from the circulation. Thus the exact magnitude of PSA production by prostate cancer cells is not easily measured. The PSA complexed to A2M is unable to cleave proteins but maintains the ability to cleave small peptide substrates. Thus, in advanced prostate cancer, sufficient PSA-A2M may be in circulation to effect total A2M levels, levels of cytokines bound to A2M and hydrolyze small circulating peptide hormones.

METHODS

Total A2M levels in men with advanced prostate cancer and PSA levels above 1000 ng/mL were measured by ELISA and compared to controls. Additional ELISA assays were used to measure levels of IL-6 and TGF-beta which can bind to A2M. The ability of PSA-A2M complexes to hydrolyze protein and peptide substrates was analyzed ± PSA inhibitor. Enzymatic activity of PSA-A2M in serum of men with high PSA levels was also assayed.

RESULTS

Serum A2M levels are inversely correlated with PSA levels in men with advanced prostate cancer. Il-6 Levels are significantly elevated in men with PSA >1000 ng/mL compared to controls with PSA <0.1 ng/mL. PSA-A2M complex in serum of men with PSA levels >1000 ng/mL can hydrolyze small fluorescently labeled peptide substrates but not large proteins that are PSA substrates. PSA can hydrolyze small peptide hormones like PTHrP and osteocalcin. PSA complexed to A2M retains the ability to degrade PTHrP.

CONCLUSIONS

In advanced prostate cancer with PSA levels >1000 ng/mL, sufficient PSA-A2M is present in circulation to produce enzymatic activity against circulating small peptide hormones. Sufficient PSA is produced in advanced prostate cancer to alter total A2M levels, which can potentially alter levels of a variety of growth factors such as IL-6, TGF-beta, basic FGF, and PDGF. Alterations in levels of these cytokines and proteolytic degradation of small peptide hormones may have profound effect on host-cancer interaction.

Inhibition of human prostate smooth muscle contraction by the LIM kinase inhibitors, SR7826 and LIMKi3

BACKGROUND AND PURPOSE

In men with benign prostatic hyperplasia, increased smooth muscle tone in the prostate may lead to bladder outlet obstruction and subsequent lower urinary tract symptoms. Consequently, medical treatment aims to inhibit prostate smooth muscle contraction. However, the efficacy of the treatment options available is limited, and improved understanding of mechanisms of prostate smooth muscle contraction and identification of new targets for medical intervention are mandatory. Several studies suggest that LIM kinases (LIMKs) promote smooth muscle contraction; however, this has not yet been examined. Here, we studied effects of the LIMK inhibitors on prostate smooth muscle contraction.

EXPERIMENTAL APPROACH

Human prostate tissues were obtained from radical prostatectomy. Phosphorylation of cofilin, a LIMK substrate, was examined using a phospho-specific antibody. Smooth muscle contractions were studied in organ bath experiments.

KEY RESULTS

Real-time PCR, Western blot and immunofluorescence suggested LIMKs are expressed in smooth muscle cells of prostate tissues. Two different LIMK inhibitors, SR7826 (1 μM) and LIMKi3 (1 μM), inhibited contractions of prostate strips, which were induced by electrical field stimulation, α₁ -adrenoceptor agonists phenylephrine and methoxamine and the TXA₂ analogue, U46619. LIMK inhibition in prostate tissues and cultured stromal cells (WPMY-1) was confirmed by cofilin phosphorylation, which was reduced by SR7826 and LIMKi3. In WPMY-1 cells, SR7826 and LIMKi3 caused breakdown of actin filaments and reduced viability.

CONCLUSIONS AND IMPLICATIONS

Smooth muscle tone in the hyperplastic human prostate may underlie the effects of LIMKs, which promote contraction. Contraction of prostate strips can be inhibited by small molecule LIMK inhibitors.

The unfolded protein response in ischemic heart disease

Ischemic heart disease is a severe stress condition that causes extensive pathological alterations and triggers cardiac cell death. Accumulating evidence suggests that the unfolded protein response (UPR) is strongly induced by myocardial ischemia. The UPR is an evolutionarily conserved cellular response to cope with protein-folding stress, from yeast to mammals. Endoplasmic reticulum (ER) transmembrane sensors detect the accumulation of unfolded proteins and stimulate a signaling network to accommodate unfolded and misfolded proteins. Distinct mechanisms participate in the activation of three major signal pathways, viz. protein kinase RNA-like ER kinase, inositol-requiring protein 1, and activating transcription factor 6, to transiently suppress protein translation, enhance protein folding capacity of the ER, and augment ER-associated degradation to refold denatured proteins and restore cellular homeostasis. However, if the stress is severe and persistent, the UPR elicits inflammatory and apoptotic pathways to eliminate terminally affected cells. The ER is therefore recognized as a vitally important organelle that determines cell survival or death. Recent studies indicate the UPR plays critical roles in the pathophysiology of ischemic heart disease. The three signaling branches may elicit distinct but overlapping effects in cardiac response to ischemia. Here, we outline the findings and discuss the mechanisms of action and therapeutic potentials of the UPR in the treatment of ischemic heart disease.

Incorporation of iloprost in phospholipase-resistant phospholipid scaffold enhances its barrier protective effects on pulmonary endothelium

Correction of barrier dysfunction and inflammation in acute lung injury (ALI) represents an important problem. Previous studies demonstrate barrier-protective and anti-inflammatory effects of bioactive lipid prostacyclin and its stable analog iloprost (ILO). We generated a phospholipase resistant synthetic phospholipid with iloprost attached at the sn-2 position (ILO-PC) and investigated its biological effects. In comparison to free ILO, ILO-PC caused sustained endothelial cell (EC) barrier enhancement, linked to more prolonged activation of Rap1 and Rac1 GTPases and their cytoskeletal and cell junction effectors: cortactin, PAK1, p120-catenin and VE-cadherin. ILO and ILO-PC equally efficiently suppressed acute, Rho GTPase-dependent EC hyper-permeability caused by thrombin. However, ILO-PC exhibited more sustained barrier-protective and anti-inflammatory effects in the model of chronic EC dysfunction caused by bacterial wall lipopolysacharide (LPS). ILO-PC was also more potent inhibitor of NFκB signaling and lung vascular leak in the murine model of LPS-induced ALI. Treatment with ILO-PC showed more efficient ALI recovery over 3 days after LPS challenge than free ILO. In conclusion, this study describes a novel synthetic phospholipid with barrier-enhancing and anti-inflammatory properties superior to existing prostacyclin analogs, which may be used as a prototype for future development of more efficient treatment for ALI and other vascular leak syndromes.

FOXM1 promotes invasion and migration of colorectal cancer cells partially dependent on HSPA5 transactivation

In this study, to investigate whether endoplastic reticulum (ER) stress correlated with FOXM1 in colorectal cancer, we analysed the mRNA levels of FOXM1 and ER stress markers HSPA5 and spliced XBP1 by qRT-PCR. FOXM1 mRNA levels were found to positively correlate with HSPA5 in colorectal cancer. However, no significant correlation between FOXM1 and spliced XBP1 mRNA levels was found. Theses results suggested the positive correlation between FOXM1 and HSPA5 in colorectal cancer was not associated with ER stress. Next, we provided evidences that FOXM1 promoted HSPA5 transcription by directly binding to and stimulating HSPA5 promoter. Moreover, a FOXM1-binding site mapped between -1019 and -1012 bp of the proximal HSPA5 promoter was identified. In addition, we found that enhancement of cell migration and invasion by FOXM1 was significantly attenuated by depletion of HSPA5 in colorectal cancer cell. Furthermore, FOXM1 triggered colorectal cancer cell migration and invasion was involved in activities of cell-surface HSPA5. Lastly, our results suggested FOXM1 facilitated the activities and expressions of MMP2 and 9 associated with cell-surface HSPA5 in colorectal cancer cells. Moreover, statistically significant positive correlations between FOXM1 and MMP2 mRNA expression, between HSPA5 and MMP2 were found in colorectal cancer tissue specimens. Together, our results suggested that FOXM1-HSPA5 signaling might be considered as a novel molecular target for designing novel therapeutic regimen to control colorectal cancer metastasis and progression.

Quantitative membrane proteomics reveals a role for tetraspanin enriched microdomains during entry of human cytomegalovirus

Human cytomegalovirus (HCMV) depends on and modulates multiple host cell membrane proteins during each stage of the viral life cycle. To gain a global view of the impact of HCMV-infection on membrane proteins, we analyzed HCMV-induced changes in the abundance of membrane proteins in fibroblasts using stable isotope labeling with amino acids (SILAC), membrane fractionation and protein identification by two-dimensional liquid chromatography and tandem mass spectrometry. This systematic approach revealed that CD81, CD44, CD98, caveolin-1 and catenin delta-1 were down-regulated during infection whereas GRP-78 was up-regulated. Since CD81 downregulation was also observed during infection with UV-inactivated virus we hypothesized that this tetraspanin is part of the viral entry process. Interestingly, additional members of the tetraspanin family, CD9 and CD151, were also downregulated during HCMV-entry. Since tetraspanin-enriched microdomains (TEM) cluster host cell membrane proteins including known CMV receptors such as integrins, we studied whether TEMs are required for viral entry. When TEMs were disrupted with the cholesterol chelator methyl-β-cylcodextrin, viral entry was inhibited and this inhibition correlated with reduced surface levels of CD81, CD9 and CD151, whereas integrin levels remained unchanged. Furthermore, simultaneous siRNA-mediated knockdown of multiple tetraspanins inhibited viral entry whereas individual knockdown had little effect suggesting essential, but redundant roles for individual tetraspanins during entry. Taken together, our data suggest that TEM act as platforms for receptors utilized by HCMV for entry into cells.

Lectin BS-I inhibits cell migration and invasion via AKT/GSK-3β/β-catenin pathway in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is most common malignant cancer worldwide; however, the mortality rate of HCC remains high due to the invasion and metastasis of HCC. Thus, exploring novel treatments to prevent the invasion of HCC is needed for improving clinical outcome of this fatal disease. In this study, we identified lectin from Bandeiraea simplicifolia seeds (BS‐I) binds to metastasis‐associated HCC cell surface glycans by a lectin microarray and inhibits HCC cell migration and invasion through downregulating the matrix metalloproteinase 2 (MMP2), matrix metalloproteinase 9 (MMP9) and urokinase‐type plasminogen activator (uPA) production. These effects of BS‐I were mediated by inhibiting the activation of AKT/GSK‐3β/β‐catenin pathway and depended on specificity of lectin BS‐I binding to GalNAc. GSK3β inhibitors rescued BS‐I‐mediated inhibition of migration and invasion of HCC cell. Further, we identified that lectin BS‐I interacts with sGrp78, affects membrane localization of sGrp78 and attenuates the binding of sGrp78 and p85 to inhibit the activation of AKT/GSK‐3β/β‐catenin pathway. Overexpression of Grp78 or P85 rescues BS‐I‐mediated inhibition of migration and invasion of HCC cell. These findings demonstrated for the first time that BS‐I can act as a novel potential drug to prevent the invasion of HCC.

Cytoskeleton and nuclear lamina affection in recessive osteogenesis imperfecta: A functional proteomics perspective

Osteogenesis imperfecta (OI) is a collagen-related disorder associated to dominant, recessive or X-linked transmission, mainly caused by mutations in type I collagen genes or in genes involved in type I collagen metabolism. Among the recessive forms, OI types VII, VIII, and IX are due to mutations in CRTAP, P3H1, and PPIB genes, respectively. They code for the three components of the endoplasmic reticulum complex that catalyzes 3-hydroxylation of type I collagen α1Pro986. Under-hydroxylation of this residue leads to collagen structural abnormalities and results in moderate to lethal OI phenotype, despite the exact molecular mechanisms are still not completely clear. To shed light on these recessive forms, primary fibroblasts from OI patients with mutations in CRTAP (n=3), P3H1 (n=3), PPIB (n=1) genes and from controls (n=4) were investigated by a functional proteomic approach. Cytoskeleton and nucleoskeleton asset, protein fate, and metabolism were delineated as mainly affected. While western blot experiments confirmed altered expression of lamin A/C and cofilin-1, immunofluorescence analysis using antibody against lamin A/C and phalloidin showed an aberrant organization of nucleus and cytoskeleton. This is the first report describing an altered organization of intracellular structural proteins in recessive OI and pointing them as possible novel target for OI treatment.

SIGNIFICANCE

OI is a prototype for skeletal dysplasias. It is a highly heterogeneous collagen-related disorder with dominant, recessive and X-linked transmission. There is no definitive cure for this disease, thus a better understanding of the molecular basis of its pathophysiology is expected to contribute in identifying potential targets to develop new treatments. Based on this concept, we performed a functional proteomic study to delineate affected molecular pathways in primary fibroblasts from recessive OI patients, carrying mutations in CRTAP (OI type VII), P3H1 (OI type VIII), and PPIB (OI type IX) genes. Our analyses demonstrated the occurrence of an altered cytoskeleton and, for the first time in OI, of nuclear lamina organization. Hence, cytoskeleton and nucleoskeleton components may be considered as novel drug targets for clinical management of the disease. Finally, according to our analyses, OI emerged to share similar deregulated pathways and molecular aberrances, as previously described, with other rare disorders caused by different genetic defects. Those aberrances may provide common pharmacological targets to support classical clinical approach in treating different diseases.

Helicobacter pylori outer inflammatory protein A (OipA) suppresses apoptosis of AGS gastric cells in vitro

Outer inflammatory protein A (OipA) is an important virulence factor associated with gastric cancer and ulcer development; however, the results have not been well established and turned out to be controversial. This study aims to elucidate the role of OipA in Helicobacter pylori infection using clinical strains harbouring oipA "on" and "off" motifs. Proteomics analysis was performed on AGS cell pre-infection and postinfection with H. pylori oipA "on" and "off" strains, using liquid chromatography/mass spectrometry. AGS apoptosis and cell cycle assays were performed. Moreover, expression of vacuolating cytotoxin A (VacA) was screened using Western blotting. AGS proteins that have been suggested previously to play a role or associated with gastric disease were down-regulated postinfection with oipA "off" strains comparing to oipA "on" strains. Furthermore, oipA "off" and ΔoipA cause higher level of AGS cells apoptosis and G0/G1 cell-cycle arrest than oipA "on" strains. Interestingly, deletion of oipA increased bacterial VacA production. The capability of H. pylori to induce apoptosis and suppress expression of proteins having roles in human disease in the absence of oipA suggests that strains not expressing OipA may be less virulent or may even be protective against carcinogenesis compared those expressing OipA. This potentially explains the higher incidence of gastric cancer in East Asia where oipA "on" strains predominates.

Expansion of BCR/ABL1+ cells requires PAK2 but not PAK1

The p21‐activated kinases (PAKs) are key nodes in oncogenic signalling pathways controlling growth, survival, and motility of cancer cells. Their activity is increased in many human cancers and is associated with poor prognosis. To date, PAK deregulation has mainly been studied in solid tumours, where PAK1 and PAK4 are the main isoforms deregulated. We show that PAK1 and PAK2 are the critical isoforms in a BCR/ABL1⁺ haematopoietic malignancy. In suspension, leukaemic cells deficient for PAK1 and PAK2 undergo apoptosis, while the loss of either protein is well tolerated. Transfer of medium conditioned by shPAK2‐ but not shPAK1‐expressing leukaemic cells interferes with endothelial cell growth. We found that leukaemic cells produce exosomes containing PAK2. Transfer of isolated exosomes supports endothelial cell proliferation. In parallel, we found that leukaemic cells explicitly require PAK2 to grow towards an extracellular matrix. PAK2‐deficient cells fail to form colonies in methylcellulose and to induce lymphomas in vivo. PAK2 might therefore be the critical isoform in leukaemic cells by controlling tumour growth in a dual manner: vascularization via exosome‐mediated transfer to endothelial cells and remodelling of the extracellular matrix. This finding suggests that the PAK2 isoform represents a promising target for the treatment of haematological diseases.

Endoplasmic Reticulum Stress and Homeostasis in Reproductive Physiology and Pathology

The endoplasmic reticulum (ER), comprises 60% of the total cell membrane and interacts directly or indirectly with several cell organelles i.e., Golgi bodies, mitochondria and proteasomes. The ER is usually associated with large numbers of attached ribosomes. During evolution, ER developed as the specific cellular site of synthesis, folding, modification and trafficking of secretory and cell-surface proteins. The ER is also the major intracellular calcium storage compartment that maintains cellular calcium homeostasis. During the production of functionally effective proteins, several ER-specific molecular steps sense quantity and quality of synthesized proteins as well as proper folding into their native structures. During this process, excess accumulation of unfolded/misfolded proteins in the ER lumen results in ER stress, the homeostatic coping mechanism that activates an ER-specific adaptation program, (the unfolded protein response; UPR) to increase ER-associated degradation of structurally and/or functionally defective proteins, thus sustaining ER homeostasis. Impaired ER homeostasis results in aberrant cellular responses, contributing to the pathogenesis of various diseases. Both female and male reproductive tissues undergo highly dynamic cellular, molecular and genetic changes such as oogenesis and spermatogenesis starting in prenatal life, mainly controlled by sex-steroids but also cytokines and growth factors throughout reproductive life. These reproductive changes require ER to provide extensive protein synthesis, folding, maturation and then their trafficking to appropriate cellular location as well as destroying unfolded/misfolded proteins via activating ER-associated degradation mediated proteasomes. Many studies have now shown roles for ER stress/UPR signaling cascades in the endometrial menstrual cycle, ovarian folliculogenesis and oocyte maturation, spermatogenesis, fertilization, pre-implantation embryo development and pregnancy and parturition. Conversely, the contribution of impaired ER homeostasis by severe/prolong ER stress-mediated UPR signaling pathways to several reproductive tissue pathologies including endometriosis, cancers, recurrent pregnancy loss and pregnancy complications associated with pre-term birth have been reported. This review focuses on ER stress and UPR signaling mechanisms, and their potential roles in female and male reproductive physiopathology involving in menstrual cycle changes, gametogenesis, preimplantation embryo development, implantation and placentation, labor, endometriosis, pregnancy complications and preterm birth as well as reproductive system tumorigenesis.

GRP78 at the Centre of the Stage in Cancer and Neuroprotection

The 78-kDa glucose-regulated protein GRP78, also known as BiP and HSP5a, is a multifunctional protein with activities far beyond its well-known role in the unfolded protein response (UPR) which is activated after endoplasmic reticulum (ER) stress in the cells. Most of these newly discovered activities depend on its position within the cell. GRP78 is located mainly in the ER, but it has also been observed in the cytoplasm, the mitochondria, the nucleus, the plasma membrane, and secreted, although it is dedicated mostly to engage endogenous cytoprotective processes. Hence, GRP78 may control either UPR and macroautophagy or may activated phosphatidylinositol 3-kinase (PI3K)/AKT pro-survival pathways. GRP78 influences how tumor cells survive, proliferate, and develop chemoresistance. In neurodegeneration, endogenous mechanisms of neuroprotection are frequently insufficient or dysregulated. Lessons from tumor biology may give us clues about how boosting endogenous neuroprotective mechanisms in age-related neurodegeneration. Herein, the functions of GRP78 are revealed at the center of the stage of apparently opposite sites of the same coin regarding cytoprotection: neurodegeneration and cancer. The goal is to give a comprehensive and critical review that may serve to guide future experiments to identify interventions that will enhance neuroprotection.

Structure, biochemistry, and biology of PAK kinases

PAKs, p21-activated kinases, play central roles and act as converging junctions for discrete signals elicited on the cell surface and for a number of intracellular signaling cascades. PAKs phosphorylate a vast number of substrates and act by remodeling cytoskeleton, employing scaffolding, and relocating to distinct subcellular compartments. PAKs affect wide range of processes that are crucial to the cell from regulation of cell motility, survival, redox, metabolism, cell cycle, proliferation, transformation, stress, inflammation, to gene expression. Understandably, their dysregulation disrupts cellular homeostasis and severely impacts key cell functions, and many of those are implicated in a number of human diseases including cancers, neurological disorders, and cardiac disorders. Here we provide an overview of the members of the PAK family and their current status. We give special emphasis to PAK1 and PAK4, the prototypes of groups I and II, for their profound roles in cancer, the nervous system, and the heart. We also highlight other family members. We provide our perspective on the current advancements, their growing importance as strategic therapeutic targets, and our vision on the future of PAKs.

Antibody Targeting GRP78 Enhances the Efficacy of Radiation Therapy in Human Glioblastoma and Non-Small Cell Lung Cancer Cell Lines and Tumor Models

Purpose: Non-small cell lung cancer (NSCLC) and glioblastoma multiforme (GBM) have poor median survival. NSCLC and GBM overexpress glucose regulated protein 78 (GRP78), which has a role in radioresistance and recurrence. In this study, we determined the effect of anti-GRP78 antibody and the combined effect of the anti-GRP78 antibody with ionizing radiation (XRT) on NSCLC and GBM cell lines both in vitro and in vivoExperimental Design: NSCLC and GBM cancer cell lines were treated with anti-GRP78 antibodies and evaluated for proliferation, colony formation, cell death, and PI3K/Akt/mTOR signaling. The efficacy of anti-GRP78 antibodies on tumor growth in combination with XRT was determined in vivo in mouse xenograft models.Results: GBM and NSCLC cells treated with anti-GRP78 antibodies showed attenuated cell proliferation, colony formation, and enhanced apoptosis. GBM and NSCLC cells treated with anti-GRP78 antibodies also showed global suppression of PI3K/Akt/mTOR signaling. Combining antibody with XRT resulted in significant tumor growth delay in both NSCLC and GBM heterotopic tumor models.Conclusions: Antibodies targeting GRP78 exhibited antitumor activity and enhanced the efficacy of radiation in NSCLC and GBM both in vitro and in vivo GRP78 is a promising novel target, and anti-GRP78 antibodies could be used as an effective cancer therapy alone or in combination with XRT. Clin Cancer Res; 23(10); 2556-64. ©2016 AACR.

Glucose-regulated protein 78 contributes to the proliferation and tumorigenesis of human colorectal carcinoma via AKT and ERK pathways

Glucose-regulated protein 78 (GRP78), a molecular chaperon in the endoplasmic reticulum (ER), is overexpressed in a variety of tumor types and plays a critical role in cancer cell proliferation, migration, invasion and drug resistance. However, the mechanisms underlying the role of GRP78 in tumor carcinogenesis remain largely unknown. In the present study, we found that GRP78 knockdown in colorectal carcinoma (CRC) cells significantly inhibited cell proliferation, colony formation and tumorigenesis in vitro and in vivo. The proliferation inhibition of CRC cells by GRP78 knockdown was associated with an S phase arrest, a reduced G1/S transition, and a downregulation of phosphorylation of AKT and ERK1/2, key cell cycle regulatory proteins. In addition, GRP78 knockdown enhanced the apoptosis induced by 5-fluorouracil (5-FU) in CRC cells. Taken together, our results indicate that GRP78 plays an important role in the development and progression of CRC and may have therapeutic potential for CRC patients.