P2X7Rs: new therapeutic targets for osteoporosis

Increasing evidence suggests that both the occurrence and progression of osteoporosis are associated with inflammation, especially in primary osteoporosis. The maintenance of skeletal homeostasis is dependent on the complex regulation of bone metabolism. Numerous evidence suggested that purinoceptor networks are essential for bone homeostasis. In this review, the relationship between inflammation and the development of osteoporosis and the role of P2X7 receptor (P2X7R) in regulating the dynamic regulation of bone reconstruction were covered. We also discussed how P2X7R regulates the balance between resorption and bone formation by osteoblasts and reviewed the relevance of P2X7R polymorphisms in skeletal physiology. Finally, we analyzed potential targets of P2X7R for osteoporosis.     

Cathepsin K: A therapeutic target for bone diseases

Cathepsin K is a member of the papain family of cysteine proteases and is highly expressed in osteoclasts that mediate bone resorption. In this review, some of the known features of cathepsin K such as structure, function in bone resorption, gene regulation and its roles in physiological or pathophysiological processes are highlighted.     

A screening campaign in sea urchin egg homogenate as a platform for discovering modulators of NAADP-dependent Ca2+ signaling in human cells

The Ca²⁺ mobilizing second messenger nicotinic acid adenine dinucleotide phosphate (NAADP) regulates intracellular trafficking events, including translocation of certain enveloped viruses through the endolysosomal system. Targeting NAADP-evoked Ca²⁺ signaling may therefore be an effective strategy for discovering novel antivirals as well as therapeutics for other disorders. To aid discovery of novel scaffolds that modulate NAADP-evoked Ca²⁺ signaling in human cells, we have investigated the potential of using the sea urchin egg homogenate system for a screening campaign. Known pharmacological inhibitors of NAADP-evoked Ca²⁺ release (but not cADPR- or IP₃-evoked Ca²⁺ release) in this invertebrate system strongly correlated with inhibition of MERS-pseudovirus infectivity in a human cell line. A primary screen of 1534 compounds yielded eighteen ‘hits’ exhibiting >80% inhibition of NAADP-evoked Ca²⁺ release. A validation pipeline for these candidates yielded seven drugs that inhibited NAADP-evoked Ca²⁺ release without depleting acidic Ca²⁺ stores in a human cell line. These candidates displayed a similar penetrance of inhibition in both the sea urchin system and the human cell line, and the extent of inhibition of NAADP-evoked Ca²⁺ signals correlated well with observed inhibition of infectivity of a Middle East Respiratory syndrome coronavirus (MERS-CoV) pseudovirus. These experiments support the potential of this simple, homogenate system for screening campaigns to discover modulators of NAADP, cADPR and IP₃-dependent Ca²⁺ signaling with potential therapeutic value.     

Sorting of the v-SNARE VAMP7 in Dictyostelium discoideum: a role for more than one Adaptor Protein (AP) complex

Soluble N-ethylmaleimide-sensitive-factor Attachment protein Receptors (SNAREs) participate in the specificity of membrane fusions in the cell. The mechanisms of specific SNARE sorting are still however poorly documented. We investigated the possible role of Adaptor Protein (AP) complexes in sorting of the Dictyostelium discoideum v-SNARE VAMP7. In live cells, GFP-VAMP7 is observed in the membrane of endocytic compartments. It is also observed in the plasma membrane of a small proportion of the cells. Mutation of a potential dileucine motif dramatically increases the proportion of cells with GFP-VAMP7 in their plasma membrane, strongly supporting the participation of an AP complex in VAMP7 sorting to the endocytic pathway. A partial increase occurs in knockout cells for the medium subunits of AP-2 and AP-3 complexes, indicating a role for both AP-2 and AP-3. VAMP7, as well as its t-SNAREs partners syntaxin 8 and Vti1, are co-immunoprecipitated with each of the medium subunits of the AP-1, AP-2, AP-3 and AP-4 complexes. This result supports the conclusion that VAMP7 directly interacts with both AP-2 and AP-3. It also raises the hypothesis of an interaction with AP-1 and AP-4. GFP-VAMP7 is retrieved from the endocytic pathway at and/or before the late post-lysosomal stage through an AP-independent mechanism.     

Mouse Models of Hermansky Pudlak Syndrome: A Review

Hermansky Pudlak Syndrome (HPS) is a recessively inherited disease affecting the contents and/or the secretion of several related subcellular organelles including melanosomes, lysosomes, and platelet dense granules. It presents with disorders of pigmentation, prolonged bleeding, and ceroid deposition, often accompanied by severe fibrotic lung disease and colitis. In the mouse, the disorder is clearly multigenic, caused by at least 14 distinct mutations. Studies on the mouse mutants have defined the granule abnormalities of HPS and have shown that the disease is associated with a surprising variety of phenotypes affecting many tissues. This is an exciting time in HPS research because of the recent molecular identification of the gene causing a major form of human HPS and the expected identifications of several mouse HPS genes. Identifications of mouse HPS genes are expected to increase our understanding of intracellular vesicle trafficking, lead to discovery of new human HPS genes, and suggest diagnostic and therapeutic approaches toward the more severe clinical consequences of the disease.     

MicroRNA-148a: A potential therapeutic target for cancer

MicroRNA-148a (miR-148a) which suppresses tumor growth by directly decreasing DNMT1 expression has been demonstrated as an important role for cancer therapy. The mechanisms for miR-148a in cancer will become potential future researches.     

Antagonism of the ATP-gated P2X7 receptor: a potential therapeutic strategy for cancer

Purinergic Signalling - The P2X receptor 7 (P2X7R) is a plasma membrane receptor sensing extracellular ATP associated with a wide variety of cellular functions. It is most commonly expressed on...     

Meeting after meeting: 20 years of discoveries by the members of the Exocytosis–Endocytosis Club

Twenty years ago, a group of French cell biologists merged two scientific clubs with the aim of bringing together researchers in the fields of Endocytosis and Exocytosis. Founded in 1997, the first annual meeting of the Exocytosis Club was held in 1998. The Endocytosis Club held quarterly meetings from its founding in 1999. The first joint annual meeting of the Exocytosis–Endocytosis Club took place in Paris in April, 2001. What started as a modest gathering of enthusiastic scientists working in the field of cell trafficking has gone from strength to strength, rapidly becoming an unmissable yearly meeting, vividly demonstrating the high quality of science performed in our community and beyond. On the occasion of the 20th meeting of our club, we want to provide historic insight into the fields of exocytosis and endocytosis, and by extension, to subcellular trafficking, highlighting how French scientists have contributed to major advances in these fields. Today, the Exocytosis–Endocytosis Club represents a vibrant and friendly community that will hold its 20th meeting at the Presqu'Ile de Giens, near Toulon in the South of France, on May 11–13, 2017.     

Skp2: A novel potential therapeutic target for prostate cancer

Prostate cancer is the most frequently diagnosed tumor in men and the second most common cause of cancer-related death for males in the United States. It has been shown that multiple signaling pathways are involved in the pathogenesis of prostate cancer, such as androgen receptor (AR), Akt, Wnt, Hedgehog (Hh) and Notch. Recently, burgeoning amounts of evidence have implicated that the F-box protein Skp2 (S-phase kinase associated protein 2), a well-characterized oncoprotein, also plays a critical role in the development and progression of prostate cancer. Therefore, this review discusses the recent literature regarding the function and regulation of Skp2 in the pathogenesis of prostate cancer. Furthermore, we highlight that Skp2 may represent an attractive therapeutic target, thus warrants further development of agents to target Skp2, which could have significant therapeutic impact on prostate cancer.     

RAGE: A potential therapeutic target during FGF1 treatment of diabetes-mediated liver injury

As a serious metabolic disease, diabetes causes series of complications that seriously endanger human health. The liver is a key organ for metabolizing glucose and lipids, which substantially contributes to the development of insulin resistance and type 2 diabetes mellitus (T2DM). Exogenous fibroblast growth factor 1 (FGF1) has a great potential for the treatment of diabetes. Receptor of advanced glycation end products (RAGE) is a receptor for advanced glycation end products that involved in the development of diabetes-triggered complications. Previous study has demonstrated that FGF1 significantly ameliorates diabetes-mediated liver damage (DMLD). However, whether RAGE is involved in this process is still unknown. In this study, we intraperitoneally injected db/db mice with 0.5 mg/kg FGF1. We confirmed that FGF1 treatment not only significantly ameliorates diabetes-induced elevated apoptosis in the liver, but also attenuates diabetes-induced inflammation, then contributes to ameliorate liver dysfunction. Moreover, we found that diabetes triggers the elevated RAGE in hepatocytes, and FGF1 treatment blocks it, suggesting that RAGE may be a key target during FGF1 treatment of diabetes-induced liver injury. Thus, we further confirmed the role of RAGE in FGF1 treatment of AML12 cells under high glucose condition. We found that D-ribose, a RAGE agonist, reverses the protective role of FGF1 in AML12 cells. These findings suggest that FGF1 ameliorates diabetes-induced hepatocyte apoptosis and elevated inflammation via suppressing RAGE pathway. These results suggest that RAGE may be a potential therapeutic target for the treatment of DMLD.     

P2X7 purinoceptor alterations in dystrophic mdx mouse muscles: relationship to pathology and potential target for treatment

Duchenne muscular dystrophy (DMD) is a lethal inherited muscle disorder. Pathological characteristics of DMD skeletal muscles include, among others, abnormal Ca(2+) homeostasis and cell signalling. Here, in the mdx mouse model of DMD, we demonstrate significant P2X7 receptor abnormalities in isolated primary muscle cells and cell lines and in dystrophic muscles in vivo. P2X7 mRNA expression in dystrophic muscles was significantly up-regulated but without alterations of specific splice variant patterns. P2X7 protein was also up-regulated and this was associated with altered function of P2X7 receptors producing increased responsiveness of cytoplasmic Ca(2+) and extracellular signal-regulated kinase (ERK) phosphorylation to purinergic stimulation and altered sensitivity to NAD. Ca(2+) influx and ERK signalling were stimulated by ATP and BzATP, inhibited by specific P2X7 antagonists and insensitive to ivermectin, confirming P2X7 receptor involvement. Despite the presence of pannexin-1, prolonged P2X7 activation did not trigger cell permeabilization to propidium iodide or Lucifer yellow. In dystrophic mice, in vivo treatment with the P2X7 antagonist Coomassie Brilliant Blue reduced the number of degeneration-regeneration cycles in mdx skeletal muscles. Altered P2X7 expression and function is thus an important feature in dystrophic mdx muscle and treatments aiming to inhibit P2X7 receptor might slow the progression of this disease.     

Cytoplasmic vacuoles and bodies of the osteoclast

Summary Cytoplasmic vacuoles and bodies in the osteoclast (rat) were studied by electron microscopy. The vacuole-like structures (0.03–5 in diameter) may be classed as a) vacuoles b) coated vacuoles and c) invaginations. The cytoplasmic bodies vary in size from 0.02–3 in diameter and these may similarly be classed as a) light cytoplasmic bodies, b) dense cytoplasmic bodies, c) coated cytoplasmic bodies and d) cytoplasmic bodies containing inclusions. Both the cytoplasmic vacuoles and the bodies are limited by a triple layered membrane of about 91 Å in thickness. Their relationship to the lysosomal system and the role of this system in the osteoclast is discussed.This research was supported by the Danish Research Council. Grant no. 512–727 and 512–819.     

High-density lipoprotein functionality and breast cancer: A potential therapeutic target

Breast cancer is a major cause of death globally, and particularly in developed countries. Breast cancer is influenced by cholesterol membrane content, by affecting the signaling pathways modulating cell growth, adherence, and migration. Furthermore, steroid hormones are derived from cholesterol and these play a key role in the pathogenesis of breast cancer. Although most findings have reported an inverse association between serum high-density lipoprotein (HDL)-cholesterol level and the risk of breast cancer, there have been some reports of the opposite, and the association therefore remains unclear. HDL is principally known for participating in reverse cholesterol transport and has an inverse relationship with the cardiovascular risk. HDL is heterogeneous, with particles varying in composition, size, and structure, which can be altered under different circumstances, such as inflammation, aging, and certain diseases. It has also been proposed that HDL functionality might have a bearing on the breast cancer. Owing to the potential role of cholesterol in cancer, its reduction using statins, and particularly as an adjuvant during chemotherapy may be useful in the anticancer treatment, and may also be related to the decline in cancer mortality. Reconstituted HDLs have the ability to release chemotherapeutic drugs inside the cell. As a consequence, this may be a novel way to improve therapeutic targeting for the breast cancer on the basis of detrimental impacts of oxidized HDL on cancer development.     

Oxidative stress in ALS: a mechanism of neurodegeneration and a therapeutic target

The cause(s) of amyotrophic lateral sclerosis (ALS) is not fully understood in the vast majority of cases and the mechanisms involved in motor neuron degeneration are multi-factorial and complex. There is substantial evidence to support the hypothesis that oxidative stress is one mechanism by which motor neuron death occurs. This theory becomes more persuasive with the discovery that mutation of the anti-oxidant enzyme, superoxide dismutase 1 (SOD1), causes disease in a significant minority of cases. However, the precise mechanism(s) by which mutant SOD1 leads to motor neuron degeneration have not been defined with certainty, and trials of anti-oxidant therapies have been disappointing. Here, we review the evidence implicating oxidative stress in ALS pathogenesis, discuss how oxidative stress may affect and be affected by other proposed mechanisms of neurodegeneration, and review the trials of various anti-oxidants as potential therapies for ALS.     

Acid-sensing ion channels 3: a potential therapeutic target for pain treatment in arthritis

Acid-sensing ion channels 3 (ASIC3) is the most sensitive to such a pH change, predominantly distributed in the sensory peripheral nervous system, and strongly correlated with pain. Recently, there is increasing evidence that ASIC3 may contribute to the pathogenesis of chronic inflammatory pain diseases due to it is predominantly expressed in dorsal root ganglia (DRG) neurons making it a good candidate for a pain sensor. Elevated expression of ASIC3 was found in DRG of rodents with inflamed hind paws. In addition, it has been shown that ASIC3 gene knock-out mice (ASIC3−/−) exhibited no enhanced hyperalgesia in inflamed joint. All theses findings suggest that ASIC3 have important biological effects in inflammation that might be a promising therapeutic target for arthritis pain. In this review, we will briefly discuss the biological features of ASIC3 and summarize recent advances on the role of ASIC3 in the pathogenesis and treatment of arthritis pain.     

BMP-7: Therapeutic target for ocular fibrotic disorders

Scarring of cornea, glaucoma, after-cataract and also proliferative vitreoretinopathy(PVR) related tractional retina detachment, age related macular degeneration and diabetic retinopathy etc., which are the major and seriously impair vision diseases in eyes, with various appearance and different therapy method, but maybe they have the similar pathogenesis—fibrosis, and all the above ocular diseases can be regarded as fibrotic disorders. Thus inhibition of the fibrotic process may provide a potentially novel therapeutic approach to the treatment of these ocular diseases mentioned above. Now numerous studies have proved that BMP-7 significantly reversed renal, hepatic, pulmonary fibrosis, including inhibition of Transforming growth factor-β (TGF-β) production, suppression of epithelial-to-mesenchymal transition (EMT), and repair of severely damaged epithelial cells. So it is reasonable to refer that BMP-7 may have the same preventive effect in these ocular fibrotic disorders. A potential clinical therapy can be developed by using the anti-fibrosis effect of BMP-7.     

A role for Rab5 activity in the biogenesis of endosomal and lysosomal compartments

Rab5 is a small GTPase that plays roles in the homotypic fusion of early endosomes and regulation of intracellular vesicle transport. We show here that expression of GFP-tagged GTPase-deficient form of Rab5b (Rab5bQ79L) in NRK cells results in the sequential formation of three morphologically and functionally distinct types of endosomes. Expression of GFP-Rab5bQ79L initially caused a homotypic fusion of early endosomes accompanying a redistribution of the TGN-resident cargo molecules, and subsequent fusion with late endosomes/lysosomes, leading to the formation of giant hybrid organelles with features of early endosomes and late endosomes/lysosomes. Surprisingly, the giant endosomes gradually fragmented and shrunk, leading to the accumulation of early endosome clusters and concurrent reformation of late endosomes/lysosomes, a process accelerated by treatment with a phosphatidylinositol-3-kinase (PI(3)K) inhibitor, wortmannin. We postulate that such sequential processes reflect the biogenesis and maintenance of late endosomes/lysosomes, presumably via direct fusion with early endosomes and subsequent fission from hybrid organelles. Thus, our findings suggest a regulatory role for Rab5 in not only the early endocytic pathway, but also the late endocytic pathway, of membrane trafficking in coordination with PI(3)K activity.     

LIM kinase 1: evidence for a role in the regulation of intracellular vesicle trafficking of lysosomes and endosomes in human breast cancer cells

LIM kinase (LIMK) plays a critical role in stimulus-induced remodeling of the actin cytoskeleton by linking signals from the Rho family GTPases to changes in cofilin activity. Recent studies have shown an important role for LIMK1 signaling in tumor cell invasion through regulating actin dynamics. In this study, we investigate the role of LIMK1 in intracellular vesicle trafficking of lysosomes/endosomes. We analyzed by confocal immunofluorescence microscopy the cellular distribution of lysosomal proteins and the endocytosis of an endocytic tracer, epidermal growth factor (EGF), in LIMK1-transfected cells. We found in these cells an abnormal dispersed translocation of lysosomes stained for LIMPII and cathepsin D throughout the cytoplasm. The small punctate structures that stained for these lysosomal proteins were redistributed to the periphery of the cell. Computational 3D-image analysis of confocal immunofluorescence micrographs further demonstrated that these vesicles did not colocalize with the transferrin receptor, an early endosomal marker. Furthermore, LIMPII-positive lysosomes did not colocalize with early endosomes labeled with endocytosed Texas red-transferrin. These results indicate that there is no mixing between dispersed lysosomes and early endosomes in the LIMK1-transfected cells. Moreover, LIMK1 overexpression resulted in a marked retardation in the receptor-mediated internalization of Texas red-labeled EGF in comparison with mock-transfected cells. At 30 min after internalization, most of the Texas red-EGF staining overlapped with LIMPII-positive late endosomes/lysosomes in mock-transfected cells, whereas in LIMK1 transfectants only a small fraction of internalized EGF colocalized with LIMPII-positive structures in the perinuclear region. Taken together, the findings presented in this paper suggest that LIMK1 has a role in regulating vesicle trafficking of lysosomes and endosomes in invasive tumor cells.     

Ovarian cancer stem cell: A potential therapeutic target for overcoming multidrug resistance

The cancer stem cell (CSC) model encompasses an advantageous paradigm that in recent decades provides a better elucidation for many important biological aspects of cancer initiation, progression, metastasis, and, more important, development of multidrug resistance (MDR). Such several other hematological malignancies and solid tumors and the identification and isolation of ovarian cancer stem cells (OV-CSCs) show that ovarian cancer also follows this hierarchical model. Gaining a better insight into CSC-mediated resistance holds promise for improving current ovarian cancer therapies and prolonging the survival of recurrent ovarian cancer patients in the future. Therefore, in this review, we will discuss some important mechanisms by which CSCs can escape chemotherapy, and then review the recent and growing body of evidence that supports the contribution of CSCs to MDR in ovarian cancer.