Lipocortin V may function as a signaling protein for vascular endothelial growth factor receptor-2/Flk-1

Therapeutic Potential of Annexins in Sepsis and COVID-19

Sepsis is a continuing problem in modern healthcare, with a relatively high prevalence, and a significant mortality rate worldwide. Currently, no specific anti-sepsis treatment exists despite decades of research on developing potential therapies. Annexins are molecules that show efficacy in preclinical models of sepsis but have not been investigated as a potential therapy in patients with sepsis. Human annexins play important roles in cell membrane dynamics, as well as mediation of systemic effects. Most notably, annexins are highly involved in anti-inflammatory processes, adaptive immunity, modulation of coagulation and fibrinolysis, as well as protective shielding of cells from phagocytosis. These discoveries led to the development of analogous peptides which mimic their physiological function, and investigation into the potential of using the annexins and their analogous peptides as therapeutic agents in conditions where inflammation and coagulation play a large role in the pathophysiology. In numerous studies, treatment with recombinant human annexins and annexin analogue peptides have consistently found positive outcomes in animal models of sepsis, myocardial infarction, and ischemia reperfusion injury. Annexins A1 and A5 improve organ function and reduce mortality in animal sepsis models, inhibit inflammatory processes, reduce inflammatory mediator release, and protect against ischemic injury. The mechanisms of action and demonstrated efficacy of annexins in animal models support development of annexins and their analogues for the treatment of sepsis. The effects of annexin A5 on inflammation and platelet activation may be particularly beneficial in disease caused by SARS-CoV-2 infection. Safety and efficacy of recombinant human annexin A5 are currently being studied in clinical trials in sepsis and severe COVID-19 patients.

Annexin V expression on CD4+ T cells with regulatory function

Regulatory T (Treg) cells induce immunologic tolerance by suppressing effector functions of conventional lymphocytes in the periphery. On the other hand, immune silencing is mediated by recognition of phosphatidylserine (PS) on apoptotic cells by phagocytes. Here we describe expression of the PS-binding protein Annexin V (ANXA5) in CD4⁺  CD25^hi Treg cells at the mRNA and protein levels. CD4⁺  ANXA5⁺ T cells constitute about 0·1%-0·6% of peripheral blood CD3⁺ T cells, exhibit co-expression of several Treg markers, such as Forkhead box P3, programmed cell death protein-1, cytotoxic T-lymphocyte antigen-4 and CD38. In vitro, ANXA5⁺ Treg cells showed enhanced adhesion to PS⁺ endothelial cells. Stimulated by anti-CD3 and PS⁺ syngeneic antigen-presenting cells CD4⁺  ANXA5⁺ T cells expanded in the absence of exogenous interleukin-2. CD4⁺  ANXA5⁺ T cells suppressed CD4⁺  ANXA5^- T-cell proliferation and mammalian target of rapamycin phosphorylation, partially dependent on cell contact. CD4⁺  ANXA5⁺ T-cell-mediated suppression was allo-specific and accompanied by an increased production of anti-inflammatory mediators. In vivo, using a model of delayed type hypersensitivity, murine CD4⁺  ANXA5⁺ T cells inhibited T helper type 1 responses. In conclusion, we report for the first time expression of ANXA5 on a subset of Treg cells that might bridge classical regulatory Treg function with immune silencing.

Avenues to molecular imaging of dying cells: Focus on cancer

Successful treatment of cancer patients requires balancing of the dose, timing, and type of therapeutic regimen. Detection of increased cell death may serve as a predictor of the eventual therapeutic success. Imaging of cell death may thus lead to early identification of treatment responders and nonresponders, and to “patient‐tailored therapy.” Cell death in organs and tissues of the human body can be visualized, using positron emission tomography or single‐photon emission computed tomography, although unsolved problems remain concerning target selection, tracer pharmacokinetics, target‐to‐nontarget ratio, and spatial and temporal resolution of the scans. Phosphatidylserine exposure by dying cells has been the most extensively studied imaging target. However, visualization of this process with radiolabeled Annexin A5 has not become routine in the clinical setting. Classification of death modes is no longer based only on cell morphology but also on biochemistry, and apoptosis is no longer found to be the preponderant mechanism of cell death after antitumor therapy, as was earlier believed. These conceptual changes have affected radiochemical efforts. Novel probes targeting changes in membrane permeability, cytoplasmic pH, mitochondrial membrane potential, or caspase activation have recently been explored. In this review, we discuss molecular changes in tumors which can be targeted to visualize cell death and we propose promising biomarkers for future exploration.

A Proteomics Based Approach Reveals Differential Regulation of Visceral Adipose Tissue Proteins between Metabolically Healthy and Unhealthy Obese Patients

Obesity and the metabolic disorders that constitute metabolic syndrome are a primary cause of morbidity and mortality in the world. Nonetheless, the changes in the proteins and the underlying molecular pathways involved in the relevant pathogenesis are poorly understood. In this study a proteomic analysis of the visceral adipose tissue isolated from metabolically healthy and unhealthy obese patients was used to identify presence of altered pathway(s) leading to metabolic dysfunction. Samples were obtained from 18 obese patients undergoing bariatric surgery and were subdivided into two groups based on the presence or absence of comorbidities as defined by the International Diabetes Federation. Two dimensional difference in-gel electrophoresis coupled with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was carried out. A total of 28 proteins were identified with a statistically significant difference in abundance and a 1.5-fold change (ANOVA, p ≤ 0.05) between the groups. 11 proteins showed increased abundance while 17 proteins were decreased in the metabolically unhealthy obese compared to the healthy obese. The differentially expressed proteins belonged broadly to three functional categories: (i) protein and lipid metabolism (ii) cytoskeleton and (iii) regulation of other metabolic processes. Network analysis by Ingenuity pathway analysis identified the NFκB, IRK/MAPK and PKC as the nodes with the highest connections within the connectivity map. The top network pathway identified in our protein data set related to cellular movement, hematological system development and function, and immune cell trafficking. The VAT proteome between the two groups differed substantially between the groups which could potentially be the reason for metabolic dysfunction.

Increased alveolar soluble annexin V promotes lung inflammation and fibrosis

The causes underlying the self-perpetuating nature of idiopathic pulmonary fibrosis (IPF), a progressive and usually lethal disease, remain unknown. We hypothesised that alveolar soluble annexin V contributes to lung fibrosis, based on the observation that human IPF bronchoalveolar lavage fluid (BALF) containing high annexin V levels promoted fibroblast involvement in alveolar epithelial wound healing that was reduced when annexin V was depleted from the BALF. Conditioned medium from annexin V-treated alveolar epithelial type 2 cells (AEC2), but not annexin V per se, induced proliferation of human fibroblasts and contained pro-fibrotic, IPF-associated proteins, as well as pro-inflammatory cytokines that were found to correlate tightly (r>0.95) with annexin V levels in human BALF. ErbB2 receptor tyrosine kinase in AECs was activated by annexin V, and blockade reduced the fibrotic potential of annexin V-treated AEC-conditioned medium. In vivo, aerosol delivery of annexin V to mouse lung induced inflammation, fibrosis and increased hydroxyproline, with activation of Wnt, transforming growth factor-β, mitogen-activated protein kinase and nuclear factor-κB signalling pathways, as seen in IPF. Chronically increased alveolar annexin V levels, as reflected in increased IPF BALF levels, may contribute to the progression of IPF by inducing the release of pro-fibrotic mediators.

CIP2A regulates cancer metabolism and CREB phosphorylation in non-small cell lung cancer

The cancerous inhibitor of protein phosphatase 2A (CIP2A) is a recently characterized endogenous inhibitor of the phosphatase activity of protein phosphatase 2A (PP2A), which extends the half-life of oncogenic protein c-myc and promotes in vivo tumor growth. The function of CIP2A in cancer progression is still poorly understood. To uncover the underlying mechanism of CIP2A-mediated cell proliferation, we implemented a two-dimensional electrophoresis (2DE)-based proteomic approach to examine lung cancer cell H1299 with and without CIP2A. We found 47 proteins differentially expressed where 19 proteins were upregulated and 28 proteins were downregulated. These were categorized into functional groups such as metabolism (25%), transcriptional and translational control (23%), and the signaling pathway and protein degradation (20%). On one hand, we validate our proteomic work by measuring the metabolic change. The knockdown of CIP2A decreased the expression of LDH-A as well as the enzymatic activity, accompanying with a decreased lactate production, an increased NADH/NAD+ ratio and ROS production. On the other hand, we found that CIP2A may regulate CREB activity through bioinformatics analysis. Our following experiments showed that, CIP2A positively regulated the phosphorylation of CREB in response to the serum treatment. Therefore, our proteomic study suggested that CIP2A mediates cancer progression through the metabolic pathway and intracellular signaling cascade.

Gonadotropin releasing hormone (GnRH) enhances annexin A5 mRNA expression through mitogen activated protein kinase (MAPK) in LbetaT2 pituitary gonadotrope cells

The mechanism by which GnRH stimulates annexin A5 expression was examined with LbetaT2 gonadotrope cells. Continuous stimulation with GnRH analog (GnRHa, Des-Gly10 [Pro9]-GnRH ethylamide) transiently elevated LHbeta mRNA expression while maintaining annexin A5 mRNA at high levels for 24 h. GnRH antagonist blocked the effect of GnRHa on annexin A5. While 12-O-tetradecanoyl-phorbol-13 acetate, a protein kinase C activator, increased the expression of annexin A5 mRNA, bisindolylmaleimide, an inhibitor of protein kinase C, suppressed GnRHa-stimulated expression of annexin A5 and LHbeta mRNA. GnRHa stimulation of LHbeta mRNA was inhibited to a greater extent than annexin A5 by a calcium chelator BAPTA/AM. Although a calcium ionophore ionomycin stimulated the expression of both genes, only LHbeta was down-regulated. The MAPK kinase inhibitor PD98059 inhibited GnRHa induction of annexin A5 but not LHbeta mRNA. EGF stimulated the expression of annexin A5 mRNA but caused only a transient effect on LHbeta mRNA expression. These results indicate that GnRH stimulation of signaling pathway for annexin A5 mRNA expression is distinct from that of LHbeta mRNA and dependent more on MAPK.

In vitro modeling of matrix vesicle nucleation: synergistic stimulation of mineral formation by annexin A5 and phosphatidylserine

Annexins A5, A2, and A6 (Anx-A5, -A2, and -A6) are quantitatively major proteins of the matrix vesicle nucleational core that is responsible for mineral formation. Anx-A5 significantly activated the induction and propagation of mineral formation when incorporated into synthetic nucleation complexes made of amorphous calcium phosphate (ACP) and Anx-A5 or of phosphatidylserine (PS) plus ACP (PS-CPLX) and Anx-A5. Incorporation of Anx-A5 markedly shortened the induction time, greatly increasing the rate and overall amount of mineral formed when incubated in synthetic cartilage lymph. Constructed by the addition of Ca(2+) to PS, emulsions prepared in an intracellular phosphate buffer matched in ionic composition to the intracellular fluid of growth plate chondrocytes, these biomimetic PS-CPLX nucleators had little nucleational activity. However, incorporation of Anx-A5 transformed them into potent nucleators, with significantly greater activity than those made from ACP without PS. The ability of Anx-A5 to enhance the nucleation and growth of mineral appears to stem from its ability to form two-dimensional crystalline arrays on PS-containing monolayers. However, some stimulatory effect also may result from its ability to exclude Mg(2+) and HCO(-)(3) from nucleation sites. Comparing the various annexins for their ability to activate PS-CPLX nucleation yields the following: avian cartilage Anx-A5 > human placental Anx-A5 > avian liver Anx-A5 > or = avian cartilage Anx-A6 >> cartilage Anx-A2. The stimulatory effect of human placental Anx-A5 and avian cartilage Anx-A6 depended on the presence of PS, since in its absence they either had no effect or actually inhibited the nucleation activity of ACP. Anx-A2 did not significantly enhance mineralization.

Proliferative effect of calcitonin gene-related peptide is induced by at least five proteins as identified by proteome profiling

Calcitonin gene-related peptide is a 37 amino acid neuropeptide. Although calcitonin gene-related peptide activates a G-protein-coupled receptor, recent evidence suggests that calcitonin gene-related peptide induces more complex signaling cascades including the activation of MAP kinases [Eur J Pharmacol; 389:125-130 (2000), Neuropeptides; 34:229-233 (2000)]. However, the molecular mechanisms of this activation still remain to be elucidated. For the first time we applied a proteomics approach in order to identify molecular targets of calcitonin gene-related peptide downstream signaling in the neuroblastoma cell line SK-N-MC and identified proteins that changed either their expression, location, or their post-translational modifications in a time-dependent manner after calcitonin gene-related peptide stimulation.

Regulation of VEGF mRNA expression and protein secretion by TGF-beta2 in human retinal pigment epithelial cells

VEGF secretion by the human retinal pigment epithelium (hRPE) plays an important role in retinal and choroidal neovascularization. In this study, transforming growth factor-beta2 (TGF-beta2)-induced vascular endothelial growth factor (VEGF) gene expression was investigated in hRPE cells. Treatment of hRPE cells with TGF-beta2 for 24 and 48h as compared to 8h resulted in markedly increased VEGF secretion by fivefold and nine-fold, respectively. Induced VEGF mRNA peaked within 3h of stimulation and remained above the basal at 36h. Stimulation of VEGF expression by TGF-beta2 was blocked by cycloheximide, suggesting that de novo protein synthesis is required. Induced VEGF production was strongly inhibited by anti-inflammatory agents, dexamethasone and cyclosporin A. Despite of the weak stimulation of VEGF expression by TNF-alpha or bFGF alone, co-administration of either of these two cytokines synergized the effect of TGF-beta2 on VEGF mRNA expression and protein production. Quantitative RT-PCR revealed that the synergy was predominantly at the level of VEGF transcription. Moreover, TGF-beta2-induced RPE VEGF secretion was significantly reduced by inhibitors of mitogen-activated protein (MAP) kinase (MEK) (U0126), p38 (SB202190), c-Jun NH2-terminal kinase (JNK), Sp600125, protein tyrosine kinase (PTK) (Genistein), and phosphatidylinositol 3-kinase (PI3K) (Ly294002). Induced VEGF expression was completely abrogated by inhibitors of protein kinase C (PKC) (Ro318220), nuclear factor-kappaB (NF-kappaB) [caffeic acid phenethyl ester (CAPE)], and reactive oxygen species (ROS) [N-acetyl-cysteine (Nac) and diphenyleneiodonium (DPI)]. These results suggest that MEK, p38, JNK, PI3K, and NF-kappaB as well as multiple essential signaling intermediates, including PKC, PTK and ROS, are involved in hRPE VEGF up regulation by TGF-beta2.

Decreased expression of annexin A1 is correlated with breast cancer development and progression as determined by a tissue microarray analysis

Annexin A1 (ANXA1) is a calcium- and phospholipid-binding protein and a known mediator of glucocorticoid-regulated inflammatory responses. Using a combined multiple high-throughput approach, we recently identified a reduced expression of ANXA1 in human breast cancer. The finding was confirmed at the gene level by quantitative reverse transcription-polymerase chain reaction and at the protein level by immunohistochemical staining of normal, benign, and malignant breast tissues. In this study, we constructed and used a high-density human breast cancer tissue microarray to characterize the expressional pattern of ANXA1 according to histopathologies. The tissue microarray contains 1,158 informative breast tissue cores of different histologies including normal tissues, hyperplasia, in situ and invasive tumors, and lymph node metastases. Our results showed that there was a significant decrease in glandular expression of ANXA1 in ductal carcinoma in situ and invasive ductal carcinoma compared with either normal breast tissue or hyperplasia (P < .0001). Moreover, in benign breast tissue, myoepithelial cells showed strong expression of ANXA1. There was a decrease of ANXA1 expression in myoepithelial cells in ductal carcinoma in situ lesions compared with the same cell population in either normal or hyperplastic lesions. These results suggest that suppressed ANXA1 expression in breast tissue is correlated with breast cancer development and progression.

Annexin V associates with the IFN-gamma receptor and regulates IFN-gamma signaling

Many of the biological activities of IFN-gamma are mediated through the IFN-gammaR3-linked Jak-Stat1alpha pathway. However, regulation of IFN-gamma signaling is not fully understood, and not all responses to IFN-gamma are Stat1alpha dependent. To identify novel elements involved in IFN-gamma cell regulation, the cytoplasmic domain of the R2 subunit of the human IFN-gammaR was used as bait in a yeast two-hybrid screen of a human monocyte cDNA library. This identified annexin A5 (AxV) as a putative IFN-gammaR binding protein. The interaction was confirmed in pull-down experiments in which a GST-R2 cytoplasmic domain fusion protein was incubated with macrophage lysates. Furthermore, immunoprecipitation using anti-IFN-gammaR2 Abs showed that AxV interacted with IFN-gammaR2 to form a stable complex following incubation of cells with IFN-gamma. In 293T cells with reduced expression of AxV, brought about by small interfering RNA targeting, activation of Jak2 and Stat1alpha in response to IFN-gamma was enhanced. Inhibition of cell proliferation, a hallmark of the IFN-gamma response, also was potentiated in HeLa cells treated with small interfering RNA directed at AxV. Taken together, these results suggest that through an inducible association with the R2 subunit of the IFN-gammaR, AxV modulates cellular responses to IFN-gamma by modulating signaling through the Jak-Stat1 pathway.

[A proteomic approach to study of the function of the Sec14p-like p45 protein]

We undertook a search for proteins interacting with protein p45 by the method of two-hybrid screening in order to determine the function of the Sec14p-like protein p45. A screening of the yeast library of rat lung cDNA, six proteins specifically activating the reporter genes of a two-hybrid system and 21 unlikely protein partners of protein p45 were identified. The most likely candidate for the role of a p45 partner is the surfactant protein C (Sftpc). These results and previous studies led us to the hypothesis that protein p45 fulfills its protective function by participating in the biogenesis of cell membranes. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2005, vol. 31, no. 3; see also http://www.maik.ru.

Prolactin inhibits annexin 5 expression and apoptosis in the corpus luteum of pseudopregnant rats: involvement of local gonadotropin-releasing hormone

We investigated a specific relationship between the expression of annexin 5 and prolactin in the corpus luteum of pseudopregnant rats, with particular interest in GnRH and apoptosis of luteal cells. The expression of ovarian annexin 5 mRNA was significantly decreased at mid-pseudopregnancy and recovered at the end, whereas it remained low on the corresponding day of pregnancy. The dopamine agonist CB-154, administered at mid-pseudopregnancy (d 5), increased ovarian annexin 5 mRNA, whereas prolactin, given daily for 3 d to cycling rats, decreased it. An immunocytochemical study also showed that annexin 5 increased in the corpus luteum on d 6 and 7 of pseudopregnancy after treatment with CB-154 on d 5. The distribution of annexin 5-positive cells was not uniform in the corpus luteum and matched that of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL)-positive cells. Because GnRH stimulates annexin 5 mRNA expression in the gonadotropes, involvement of the GnRH receptor was examined. Local administration of a GnRH antagonist, Cetrorelix, to hemilateral ovarian bursa of pseudopregnant rats simultaneously receiving CB-154 abrogated both the expression of annexin 5 and the TUNEL reaction. The present results clearly demonstrate that prolactin decreases annexin 5 mRNA in the luteal cells during pseudopregnancy. Prolactin is suggested to suppress the local action of GnRH, which stimulates annexin 5 synthesis and apoptosis of functional luteal cells during pseudopregnancy.

Circadian programs of transcriptional activation, signaling, and protein turnover revealed by microarray analysis of mammalian cells

Many aspects of physiology and behavior are temporally organized into daily 24 hr rhythms, driven by an endogenous circadian clock. Studies in eukaryotes have identified a network of interacting genes forming interlocked autoregulatory feedback loops which underlie overt circadian organization in single cells. While in mammals the master oscillator resides in the suprachiasmatic nuclei of the hypothalamus, semiautonomous circadian oscillators also exist in peripheral tissues and in immortalized fibroblasts, where rhythmicity is induced following a serum shock. We used this model system in combination with high-density cDNA microarrays to examine the magnitude and quality of clock control of gene expression in mammalian cells. Supported by application of novel bioinformatics tools, we find approximately 2% of genes, including expected canonical clock genes, to show consistent rhythmic circadian expression across five independent experiments. Rhythmicity in most of these genes is novel, and they fall into diverse functional groups, highlighted by a predominance of transcription factors, ubiquitin-associated factors, proteasome components, and Ras/MAPK signaling pathway components. When grouped according to phase, 68% of the genes were found to peak during estimated subjective day, 32% during estimated subjective night, with a tendency to peak at a phase corresponding to anticipation of dawn or dusk.

Annexins: from structure to function

Annexins are Ca2+ and phospholipid binding proteins forming an evolutionary conserved multigene family with members of the family being expressed throughout animal and plant kingdoms. Structurally, annexins are characterized by a highly alpha-helical and tightly packed protein core domain considered to represent a Ca2+-regulated membrane binding module. Many of the annexin cores have been crystallized, and their molecular structures reveal interesting features that include the architecture of the annexin-type Ca2+ binding sites and a central hydrophilic pore proposed to function as a Ca2+ channel. In addition to the conserved core, all annexins contain a second principal domain. This domain, which NH2-terminally precedes the core, is unique for a given member of the family and most likely specifies individual annexin properties in vivo. Cellular and animal knock-out models as well as dominant-negative mutants have recently been established for a number of annexins, and the effects of such manipulations are strikingly different for different members of the family. At least for some annexins, it appears that they participate in the regulation of membrane organization and membrane traffic and the regulation of ion (Ca2+) currents across membranes or Ca2+ concentrations within cells. Although annexins lack signal sequences for secretion, some members of the family have also been identified extracellularly where they can act as receptors for serum proteases on the endothelium as well as inhibitors of neutrophil migration and blood coagulation. Finally, deregulations in annexin expression and activity have been correlated with human diseases, e.g., in acute promyelocytic leukemia and the antiphospholipid antibody syndrome, and the term annexinopathies has been coined.