Cytoskeleton-associated gelsolin responds to the midgut distention process in saline meal-fed Aedes aegypti and affects arbovirus dissemination from the midgut.

The mosquito, Aedes aegypti, is the principal vector for several arboviruses. The mosquito midgut is the initial tissue that gets infected with an arbovirus acquired along with a blood meal from a vertebrate host. Blood meal ingestion leads to midgut tissue distention thereby increasing the pore size of the surrounding basal lamina. This allows newly synthesized virions to exit the midgut by traversing the distended basal lamina to infect secondary tissues of the mosquito. We conducted a quantitative label-free proteomic time course analysis with saline meal-fed Ae. aegypti females to identify host factors involved in midgut tissue distention. Around 2000 proteins were detected during each of the seven sampling time points and 164 of those were uniquely expressed. Forty-five of 97 differentially expressed proteins were upregulated during the 96-h time course and most of those were involved in cytoskeleton modulation, metabolic activity, and vesicle/vacuole formation. The F-actin-modulating Ae. aegypti (Aa)-gelsolin was selected for further functional studies. Stable knockout of Aa-gelsolin resulted in a mosquito line, which showed distorted actin filaments in midgut-associated tissues likely due to diminished F-actin processing by gelsolin. Zika virus dissemination from the midgut of these mosquitoes was diminished and delayed. The loss of Aa-gelsolin function was associated with an increased induction of apoptosis in midgut tissue indicating an involvement of Aa-gelsolin in apoptotic signaling in mosquitoes. Here, we used proteomics to discover a novel host factor, Aa-gelsolin, which affects the midgut escape barrier for arboviruses in mosquitoes and apoptotic signaling in the midgut.

Epitope-specific antibody fragments block aggregation of AGelD187N, an aberrant peptide in gelsolin amyloidosis.

Aggregation of aberrant fragment of plasma gelsolin, AGelD187N, is a crucial event underlying the pathophysiology of Finnish gelsolin amyloidosis, an inherited form of systemic amyloidosis. The amyloidogenic gelsolin fragment AGelD187N does not play any physiological role in the body, unlike most aggregating proteins related to other protein misfolding diseases. However, no therapeutic agents that specifically and effectively target and neutralize AGelD187N exist. We used phage display technology to identify novel single-chain variable fragments that bind to different epitopes in the monomeric AGelD187N that were further maturated by variable domain shuffling and converted to antigen-binding fragment (Fab) antibodies. The generated antibody fragments had nanomolar binding affinity for full-length AGelD187N, as evaluated by biolayer interferometry. Importantly, all four Fabs selected for functional studies efficiently inhibited the amyloid formation of full-length AGelD187N as examined by thioflavin fluorescence assay and transmission electron microscopy. Two Fabs, neither of which bound to the previously proposed fibril-forming region of AGelD187N, completely blocked the amyloid formation of AGelD187N. Moreover, no small soluble aggregates, which are considered pathogenic species in protein misfolding diseases, were formed after successful inhibition of amyloid formation by the most promising aggregation inhibitor, as investigated by size-exclusion chromatography combined with multiangle light scattering. We conclude that all regions of the full-length AGelD187N are important in modulating its assembly into fibrils and that the discovered epitope-specific anti-AGelD187N antibody fragments provide a promising starting point for a disease-modifying therapy for gelsolin amyloidosis, which is currently lacking.

Plasma Gelsolin Inhibits Natural Killer Cell Function and Confers Chemoresistance in Epithelial Ovarian Cancer.

Plasma gelsolin (pGSN) overexpression in ovarian cancer (OVCA) disarms immune function, contributing to chemoresistance. The aim of this study was to investigate the immunoregulatory effects of pGSN expression on natural killer (NK) cell function in OVCA. OVCA tissues from primary surgeries underwent immunofluorescent staining of pGSN and the activated NK cell marker natural cytotoxicity triggering receptor 1 to analyze the prognostic impact of pGSN expression and activated NK cell infiltration. The immunoregulatory effects of pGSN on NK cells were assessed using apoptosis assay, cytokine secretion, immune checkpoint-receptor expression, and phosphorylation of STAT3. In OVCA tissue analyses, activated NK cell infiltration provided survival advantages to patients. However, high pGSN expression attenuated the survival benefits of activated NK cell infiltration. In the in vitro experiment, pGSN in OVCA cells induced NK cell death through cell-to-cell contact. pGSN increased T-cell immunoglobulin and mucin-domain-containing-3 expression (TIM-3) on activated NK cells. Further, it decreased interferon-γ production in activated TIM-3+ NK cells, attenuating their anti-tumor effects. Thus, increased pGSN expression suppresses the anti-tumor functions of NK cells. The study provides insights into why immunotherapy is rarely effective in patients with OVCA and suggests novel treatment strategies.

Gelsolin regulates receptor-mediated and fluid-phase endocytosis in platelets.

BACKGROUND: Endocytosis is the process by which platelets incorporate extracellular molecules into their secretory granules. Endocytosis is mediated by the actin cytoskeleton in nucleated cells; however, the endocytic mechanisms in platelets are undefined. OBJECTIVES: To better understand platelet endocytosis, we studied gelsolin (Gsn), an actin-severing protein that promotes actin assembly. METHODS: Mouse platelets from Gsn-null (Gsn-/-) and wild-type (WT) controls were used. The uptake of fluorescent cargo molecules was compared as a measure of their endocytic efficiency. Receptor-mediated endocytosis was measured by the uptake of fibrinogen and transferrin; fluid-phase endocytosis was monitored by the uptake of fluorescent dextrans. RESULTS: Adenosine diphosphate (ADP)-stimulated WT platelets readily internalized both receptor-mediated and fluid-phase cargoes. In contrast, Gsn-/- platelets showed a severe defect in the endocytosis of both types of cargo. The treatment of WT platelets with the actin-disrupting drugs cytochalasin D and jasplakinolide also reduced endocytosis. Notably, the individual and combined effects of Gsn deletion and drug treatment were similar for both receptor-mediated and fluid-phase endocytosis, indicating that Gsn mediates endocytosis via its action on the actin cytoskeleton. CONCLUSION: Our study demonstrates that Gsn plays a key role in the uptake of bioactive mediators by platelets.

Reorganization of the actin cytoskeleton during the formation of neutrophil extracellular traps (NETs).

We analyzed actin cytoskeleton alterations during NET extrusion by neutrophil-like dHL-60 cells and human neutrophils in the absence of DNase1 containing serum to avoid chromatin degradation and microfilament disassembly. NET-formation by dHL-60 cells and neutrophils was induced by Ionomycin or phorbol-12-myristat-13-acetate (PMA). Subsequent staining with anti-actin and TRITC-phalloidin showed depolymerization of the cortical F-actin at spatially confined areas, the NET extrusion sites, effected by transient activation of the monooxygenase MICAL-1 supported by the G-actin binding proteins cofilin, profilin, thymosin ß4 and probably the F-actin fragmenting activity of gelsolin and/or its fragments, which also decorated the formed NETs. MICAL-1 itself appeared to be proteolyzed by neutrophil elastase possibly to confine its activity to the NET-extrusion area. The F-actin oxidization activity of MICAL-1 is inhibited by Levosimendan leading to reduced NET-formation. Anti-gasdermin-D immunohistochemistry showed a cytoplasmic distribution in non-stimulated cells. After stimulation the NET-extrusion pore displayed reduced anti-gasdermin-D staining but accumulated underneath the plasma membrane of the remaining cell body. A similar distribution was observed for myosin that concentrated together with cortical F-actin along the periphery of the remaining cell body suggesting force production by acto-myosin interactions supporting NET expulsion as indicated by the inhibitory action of the myosin ATPase inhibitor blebbistatin. Isolated human neutrophils displayed differences in their content of certain cytoskeletal proteins. After stimulation neutrophils with high gelsolin content preferentially formed "cloud"-like NETs, whereas those with low or no gelsolin formed long "filamentous" NETs.

Maize actin depolymerizing factor 1 (ZmADF1) negatively regulates pollen development.

The normal development of pollen grains and the completion of double fertilization in embryos are crucial for both the sexual reproduction of angiosperms and grain production. Actin depolymerizing factor (ADF) regulates growth, development, and responses to biotic and abiotic stress by binding to actin in plants. In this study, the function of the ZmADF1 gene was validated through bioinformatic analysis, subcellular localization, overexpression in maize and Arabidopsis, and knockout via CRISPR/Cas9. The amino acid sequence of ZmADF1 exhibited high conservation and a similar tertiary structure to that of ADF homologs. Subcellular localization analysis revealed that ZmADF1 is localized mainly to the nucleus and cytoplasm. The ZmADF1 gene was specifically expressed in maize pollen, and overexpression of the ZmADF1 gene decreased the number of pollen grains in the anthers of transgenic Arabidopsis plants. The germination rate of pollen and the empty seed shell rate in the fruit pods of the overexpressing plants were significantly greater than those in the wild-type (WT) plants. In maize, the pollen viability of the knockout lines was significantly greater than that of both the WT and the overexpressing lines. Our results confirmed that the ZmADF1 gene was specifically expressed in pollen and negatively regulated pollen quantity, vigor, germination rate, and seed setting rate. This study provides insights into ADF gene function and possible pathways for improving high-yield maize breeding.

The regulation of plasma gelsolin by DNA methylation in ovarian cancer chemo-resistance.

BACKGROUND: Ovarian cancer (OVCA) is the most lethal gynecologic cancer and chemoresistance remains a major hurdle to successful therapy and survival of OVCA patients. Plasma gelsolin (pGSN) is highly expressed in chemoresistant OVCA compared with their chemosensitive counterparts, although the mechanism underlying the differential expression is not known. Also, its overexpression significantly correlates with shortened survival of OVCA patients. In this study, we investigated the methylation role of Ten eleven translocation isoform-1 (TET1) in the regulation of differential pGSN expression and chemosensitivity in OVCA cells. METHODS: Chemosensitive and resistant OVCA cell lines of different histological subtypes were used in this study to measure pGSN and TET1 mRNA abundance (qPCR) as well as protein contents (Western blotting). To investigate the role of DNA methylation specifically in pGSN regulation and pGSN-induced chemoresistance, DNMTs and TETs were pharmacologically inhibited in sensitive and resistant OVCA cells using specific inhibitors. DNA methylation was quantified using EpiTYPER MassARRAY system. Gain-and-loss-of-function assays were used to investigate the relationship between TET1 and pGSN in OVCA chemoresponsiveness. RESULTS: We observed differential protein and mRNA expressions of pGSN and TET1 between sensitive and resistant OVCA cells and cisplatin reduced their expression in sensitive but not in resistant cells. We observed hypomethylation at pGSN promoter upstream region in resistant cells compared to sensitive cells. Pharmacological inhibition of DNMTs increased pGSN protein levels in sensitive OVCA cells and decreased their responsiveness to cisplatin, however we did not observe any difference in methylation level at pGSN promoter region. TETs inhibition resulted in hypermethylation at multiple CpG sites and decreased pGSN protein level in resistant OVCA cells which was also associated with enhanced response to cisplatin, findings that suggested the methylation role of TETs in the regulation of pGSN expression in OVCA cells. Further, we found that TET1 is inversely related to pGSN but positively related to chemoresponsiveness of OVCA cells. CONCLUSION: Our findings broaden our knowledge about the epigenetic regulation of pGSN in OVCA chemoresistance and reveal a novel potential target to re-sensitize resistant OVCA cells. This may provide a future therapeutic strategy to improve the overall OVCA patient survival.

miRn-3 inhibits cutaneous wound healing by targeting gelsolin in the sea cucumber Apostichopus japonicus.

The microRNA novel-3 (miRn-3) is a 23-nt small endogenous noncoding RNA of unknown function. To enrich our knowledge of the regulatory function of miRn-3 in the process of wound healing, the sea cucumber Apostichopus japonicus was used as a target model in this study. Gelsolin (AjGSN), a potential target gene of miRn-3, was cloned and characterized, and the interaction between miRn-3 and AjGSN was verified. The function of the miRn-3/AjGSN axis in regulating cutaneous wound healing was explored in the sea cucumber A. japonicus. The results showed that 1) the full-length cDNA of AjGSN was 2935 bp, with a high level of sequence conservation across the echinoderms; 2) miRn-3 could bind to the 3'UTR of AjGSN and negatively regulate the expression of AjGSN; 3) overexpression of miRn-3 and inhibition of the expression of AjGSN suppressed cutaneous wound healing in A. japonicus. In general, all observations of this study suggest that miRn-3 plays an important role in the early process of cutaneous wound healing by negatively targeting AjGSN, and that it may be a potential biomarker in wound healing.

UV-LASER adjuvant-surfactant-facilitated delivery of mobile dsRNA to tomato plant vasculature and evidence of biological activity by gene knockdown in the potato psyllid.

BACKGROUND: Double-stranded RNA (dsRNA) biopesticides are of interest for the abatement of insect vectors of pathogenic bacteria such as 'Candidatus Liberibacter', which infects both its psyllid and plant hosts. Silencing of genes essential for psyllids, or for Liberibacter, is anticipated to lead to mortality or impeded bacterial multiplication. Foliar delivery is preferred for biopesticide application; however, the cuticle impedes dsRNA penetration into the vasculature. Here, conditions were established for wounding tomato leaves using ultraviolet light amplification by stimulated emissions of radiation (UV-LASER) to promote dsRNA penetration into leaves and vasculature. RESULTS: UV-LASER treatment with application of select adjuvants/surfactants resulted in vascular delivery of 100-, 300- and 600-bp dsRNAs that, in general, were correlated with size. The 100-bp dsRNA required no pretreatment, whereas 300- and 600-bp dsRNAs entered the vasculature after UV-LASER treatment only and UV-LASER adjuvant/surfactant treatment, respectively. Of six adjuvant/surfactants evaluated, plant-derived oil combined with an anionic organosilicon compound performed most optimally. Localization of dsRNAs in the tomato vasculature was documented using fluorometry and fluorescence confocal microscopy. The biological activity of in planta-delivered dsRNA (200-250 bp) was determined by feeding third-instar psyllids on tomato leaves post UV-LASER adjuvant/surfactant treatment, with or without psyllid cdc42- and gelsolin dsRNAs. Gene knockdown was quantified by quantitative, real-time polymerase chain reaction with reverse transcription (RT-qPCR) amplification. At 10 days post the ingestion-access period, knockdown of cdc42 and gelsolin expression was 61% and 56%, respectively, indicating that the dsRNAs delivered to the tomato vasculature were mobile and biologically active. CONCLUSION: Results indicated that UV-LASER adjuvant/surfactant treatments facilitated the delivery of mobile, biologically active dsRNA molecules to the plant vasculature. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Gelsolin, an Actin-Binding Protein: Bioinformatic Analysis and Functional Significance in Urothelial Bladder Carcinoma.

The involvement of the actin-regulatory protein, gelsolin (GSN), in neoplastic transformation has been reported in different cancers including bladder cancer. However, the exact mechanism by which GSN influences bladder cancer development is not well understood. Here, we sought to reveal the functional significance of GSN in bladder cancer by undertaking a comprehensive bioinformatic analysis of TCGA datasets and through the assessment of multiple biological functions. GSN expression was knocked down in bladder cancer cell lines with two siRNA isoforms targeting GSN. Proliferation, migration, cell cycle and apoptosis assays were carried out. GSN expression, enrichment analysis, protein-protein interaction and immune infiltration analysis were verified through online TCGA tools. The data indicated that GSN expression is associated with bladder cancer proliferation, migration and enhanced cell apoptosis through regulation of NF-κB expression. GSN expression correlated with various inflammatory cells and may influence the immunity of the tumor microenvironment. Computational analysis identified several interacting partners which are associated with cancer progression and patient outcome. The present results demonstrate that GSN plays an important role in bladder cancer pathogenesis and may serve as a potential biomarker and therapeutic target for cancer therapy.

Gelsolin from mussel's catch muscle.

Proteins of the gelsolin family are Ca2+-dependent, multifunctional, actin-binding proteins containing three (S1-S3, about 40 kDa) or six (S1-S6, about 80 kDa) highly conserved repeats in the amino acid sequence. The pattern of interaction of these proteins with actin is complex: they can sever actin filaments; promote polymer nucleation after binding to two actin monomers; and cap the growing barbed end of actin filaments. In the present study, an actin polymerizing factor (46 kDa) from the adductor muscle of a bivalve mollusc has been discovered and identified for the first time. This protein has turned out to belong to the gelsolin family of actin regulatory proteins. The expression of gelsolin-like proteins in the tissues of bivalves was predicted after analyzing their proteome, but this is the first study where an actually expressed protein has been found. A primary determination of its physicochemical properties such as molecular weight, charge, resistance to urea, influence on actin polymerization by viscosity, and light scattering is carried out and the molecular structure analyzed.

Purification of modified mammalian actin isoforms for in vitro reconstitution assays.

In vitro reconstitution assays using purified actin have greatly improved our understanding of cytoskeletal dynamics and their regulation by actin-binding proteins. However, early purification methods consisted of harsh conditions to obtain pure actin and often did not include correct maturation and obligate modification of the isolated actin monomers. Novel insights into the folding requirements and N-terminal processing of actin as well as a better understanding of the interaction of actin with monomer sequestering proteins such as DNaseI, profilin and gelsolin, led to the development of more gentle approaches to obtain pure recombinant actin isoforms with known obligate modifications. This review summarizes the approaches that can be employed to isolate natively folded endogenous and recombinant actin from tissues and cells. We further emphasize the use and limitations of each method and describe how these methods can be implemented to study actin PTMs, disease-related actin mutations and novel actin-like proteins.

Cryopreservation, in addition to protein tyrosine phosphorylation, alters the distribution of phosphatidyl inositol bisphosphate and the localization of cytoskeletal and signaling proteins (gelsolin, tyrosine kinase c-SRC and phospholipase C-ζ) in the perinuclear theca of boar sperm.

Cryopreservation of boar spermatozoa affects the perinuclear theca (PT) and involves several proteins and molecules that play important roles during capacitation and the acrosomal reaction. The objective of the present study was to evaluate whether the deleterious effects of cryopreservation in addition to protein tyrosine phosphorylation are accompanied by changes in the distribution of phosphatidyl inositol bisphosphate (PIP2) and the localization of cytoskeletal and signaling proteins in the perinuclear theca of cryopreserved boar spermatozoa. For this purpose, by immunocytochemistry (IC) the changes in localization of phosphorylated proteins in tyrosine residues, gelsolin, c-SRC kinase and PLC-ζ, as well as in the distribution of phosphatidyl inositol bisphosphate were analyzed in thawed spermatozoa (T) non capacitated (NC), capacitated (C) and in those with acrosomal reaction (AR) and compared with fresh spermatozoa (F) under the same physiological status. Western blotting (WB) and co-immunoprecipitation were performed to confirm the presence of these proteins in PT and to determine the interaction between these molecules. IC showed that immunostaining for phosphorylated proteins significantly increased in the acrosomal region and flagellum in TNC spermatozoa (p < 0.05). The proportion of cells displaying immunolabeling for gelsolin in the acrosomal region decreased after capacitation in cryopreserved spermatozoa; the same change was found (p < 0.05) in the proportion of spermatozoa immunoreactive to PIP2 in the sperm head. c-SRC was observed in the equatorial segment and acrosomal region, subdomains that coincide with the site where phosphorylated proteins were detected. PLC-ζ immunolocalization in fresh spermatozoa underwent changes after capacitation and acrosomal reaction, with a significant increase in the equatorial segment and post-acrosomal region in cryopreserved spermatozoa (p < 0.05). WB analysis indicated the presence of gelsolin, c-SRC and PLC-ζ in PT; besides, we confirmed that gelsolin co-immunoprecipitated with c-SRC and PLC-ζ, which changes according to the physiological state of spermatozoa. As a conclusion, cryopreservation together with increased immunodetection of tyrosine phosphorylated proteins decreases the detection of PIP2 and alters the immunolocalization patterns of gelsolin, c-SRC and PLC-ζ in the PT in boar spermatozoa.

Early pregnancy biomarker discovery study for spontaneous preterm birth.

(1) OBJECTIVE: discover new candidate biomarkers for spontaneous preterm birth in early pregnancy samples. When fully clinically validated, early pregnancy biomarkers for sPTB give the possibility to intervene or monitor high-risk pregnancies more intensively through, as example, pelvic exams, ultrasound or sonographic cervical length surveillance. (2) STUDY DESIGN: Early pregnancy serum samples of eight spontaneous extreme and very preterm birth cases (<32 weeks of gestational age) without any symptoms of preeclampsia and fetal growth restriction and eight uncomplicated pregnancies were analyzed by liquid chromatography mass spectrometry (LC-MS). Thirteen proteins, which were differentially expressed according to the LC-MS data, were subsequently selected for confirmation by enzyme-linked immunosorbent assay (ELISA). (3) RESULTS: Differential expression of four candidate biomarkers was confirmed by ELISA with decreased early pregnancy levels of gelsolin and fibulin-1 and increased levels of c-reactive protein and complement C5 in the preterm birth group. (4) CONCLUSIONS: The confirmed candidate biomarkers are all to some extent related to inflammatory pathways and/or the complement system. This supports the hypothesis that both play a role in extreme and very preterm birth without any symptoms of preeclampsia and fetal growth restriction. The predictive value of complement C5, c-reactive protein, fibulin-1 and gelsolin should, therefore, be validated in another cohort with early pregnancy samples.

Hereditary gelsolin amyloidosis: a rare cause of cranial, peripheral and autonomic neuropathies linked to D187N and Y447H substitutions.

INTRODUCTION: Hereditary gelsolin (AGel) amyloidosis is a systemic disease that is characterised by neurologic, ophthalmologic, dermatologic, and other organ involvements. We describe the clinical features with a focus on neurological manifestations in a cohort of patients with AGel amyloidosis referred to the Amyloidosis Centre in the United States. METHODS: Fifteen patients with AGel amyloidosis were included in the study between 2005 and 2022 with the permission of the Institutional Review Board. Data were collected from the prospectively maintained clinical database, electronic medical records and telephone interviews. RESULTS: Neurologic manifestations were featured in 15 patients: cranial neuropathy in 93%, peripheral and autonomic neuropathy in 57% and bilateral carpal tunnel syndrome in 73% of cases. A novel p.Y474H gelsolin variant featured a unique clinical phenotype that differed from the one associated with the most common variant of AGel amyloidosis. DISCUSSION: We report high rates of cranial and peripheral neuropathy, carpal tunnel syndrome and autonomic dysfunction in patients with systemic AGel amyloidosis. The awareness of these features will enable earlier diagnosis and timely screening for end-organ dysfunction. The characterisation of pathophysiology will assist the development of therapeutic options in AGel amyloidosis.

mTORC2 interactome and localization determine aggressiveness of high-grade glioma cells through association with gelsolin.

mTOR complex 2 (mTORC2) has been implicated as a key regulator of glioblastoma cell migration. However, the roles of mTORC2 in the migrational control process have not been entirely elucidated. Here, we elaborate that active mTORC2 is crucial for GBM cell motility. Inhibition of mTORC2 impaired cell movement and negatively affected microfilament and microtubule functions. We also aimed to characterize important players involved in the regulation of cell migration and other mTORC2-mediated cellular processes in GBM cells. Therefore, we quantitatively characterized the alteration of the mTORC2 interactome under selective conditions using affinity purification-mass spectrometry in glioblastoma. We demonstrated that changes in cell migration ability specifically altered mTORC2-associated proteins. GSN was identified as one of the most dynamic proteins. The mTORC2-GSN linkage was mostly highlighted in high-grade glioma cells, connecting functional mTORC2 to multiple proteins responsible for directional cell movement in GBM. Loss of GSN disconnected mTORC2 from numerous cytoskeletal proteins and affected the membrane localization of mTORC2. In addition, we reported 86 stable mTORC2-interacting proteins involved in diverse molecular functions, predominantly cytoskeletal remodeling, in GBM. Our findings might help expand future opportunities for predicting the highly migratory phenotype of brain cancers in clinical investigations.

Role and therapeutic potential of gelsolin in atherosclerosis.

Atherosclerosis is the major pathophysiological basis of a variety of cardiovascular diseases and has been recognized as a lipid-driven chronic inflammatory disease. Gelsolin (GSN) is a member of the GSN family. The main function of GSN is to cut and seal actin filaments to regulate the cytoskeleton and participate in a variety of biological functions, such as cell movement, morphological changes, metabolism, apoptosis and phagocytosis. Recently, more and more evidences have demonstrated that GSN is Closely related to atherosclerosis, involving lipid metabolism, inflammation, cell proliferation, migration and thrombosis. This article reviews the role of GSN in atherosclerosis from inflammation, apoptosis, angiogenesis and thrombosis.

Gelsolin Inhibits the Proliferation of Colon Cancer Cells by Enhancing the Expression of TNFR2/CASP10 as a Death Receptor Pathway.

BACKGROUND: Colon cancer has the second highest incidence rate of digestive system tumors. It relies on surgical treatment, radiotherapy and chemotherapy, and targeted drug therapy. OBJECTIVE: To study the mechanism of GSN in the proliferation of colon cancer cells. MATERIALS AND METHODS: The expression of gelsolin (GSN) was analyzed with the data of colon cancer patients in the TCGA database. SW620 cells were treated by GSN in vitro and the gene expression was detected by immunoblotting and quantitative PCR. RESULTS: The expression of GSN was found significantly low in colon cancer cells and correlated with the prognosis of patients. The SW620 cell line cultured in vitro was treated with exogenous GSN. SW620 can be significantly inhibited above the concentration of 250 µg/ml. The results of immunoblotting and quantitative PCR showed that exogenous GSN can effectively improve the transcription level of death receptor-related pathway genes such as TNFR2 and CASP10. CONCLUSION: This study found that GSN inhibited the proliferation of SW620 cells in vitro by upregulating the expression of death receptor pathway-related proteins.

HIV-1 Vpr Induces Degradation of Gelsolin, a Myeloid Cell-Specific Host Factor That Reduces Viral Infectivity by Inhibiting the Expression and Packaging of the HIV-1 Env Glycoprotein.

Gelsolin (GSN) is a structural actin-binding protein that is known to affect actin dynamics in the cell. Using mass spectrometry, we identified GSN as a novel Vpr-interacting protein. Endogenous GSN protein was expressed at detectable levels in monocyte-derived macrophages (MDM) and in THP-1 cells, but it was undetectable at the protein level in other cell lines tested. The HIV-1 infection of MDM was associated with a reduction in GSN steady-state levels, presumably due to the Vpr-induced degradation of GSN. Indeed, the coexpression of GSN and Viral protein R (Vpr) in transiently transfected HEK293T cells resulted in the Vpr-dependent proteasomal degradation of GSN. This effect was observed for Vprs from multiple virus isolates. The overexpression of GSN in HEK293T cells had no effect on Gag expression or particle release, but it reduced the expression and packaging of the HIV-1 envelope (Env) glycoprotein and reduced viral infectivity. An analysis of the HIV-1 splicing patterns did not reveal any GSN-dependent differences, suggesting that the effect of GSN on Env expression was regulated at a posttranscriptional level. Indeed, the treatment of transfected cells with lysosomal inhibitors reversed the effect of GSN on Env stability, suggesting that GSN reduced Env expression via enhanced lysosomal degradation. Our data identify GSN as a macrophage-specific host antiviral factor that reduces the expression of HIV-1 Env. IMPORTANCE Despite dramatic progress in drug therapies, HIV-1 infection remains an incurable disease that affects millions of people worldwide. The virus establishes long-lasting reservoirs that are resistant to currently available drug treatments and allow the virus to rebound whenever drug therapy is interrupted. Macrophages are long-lived cells that are relatively insensitive to HIV-1-induced cytopathicity and thus could contribute to the viral reservoir. Here, we identified a novel host factor, gelsolin, that is expressed at high levels in macrophages and inhibits viral infectivity by modulating the expression of the HIV-1 Env glycoprotein, which is critical in the spread of an HIV-1 infection. Importantly, the viral protein Vpr induces the degradation of gelsolin and thus counteracts its antiviral activity. Our study provides significant and novel insights into HIV-1 virus-host interactions and furthers our understanding of the importance of Vpr in HIV-1 infection and pathogenesis.