[Evaluation of effects of comprehensive intervention based on key persons on AIDS-related high-risk behaviors in male sex workers in entertainment venues]

Objective: To evaluate the effect of comprehensive intervention model based on key persons in entertainment venues on the incidence of AIDS-related high-risk behaviors in male sex workers (MSW). Data from this study thus can be used to provide compelling evidence for the wider implementation of the intervention model. Methods: In this randomized controlled trial, MSW were recruited and followed-up from May to December, 2021 in entertainment venues in Wuxi, Jiangsu Province, with an estimated sample size of 320. The MSW in the intervention group were provided with comprehensive interventions via key persons in entertainment venues compared with the control group receiving routine interventions. The effect of the intervention model was assessed by comparing the behavioral differences between these two groups and in the intervention group before and after intervention. Results: A total of 330 MSW were recruited at baseline survey, in which 168 were divided into intervention group and 162 into control group. There was no significant difference in socio-demographic characteristics between two groups (all P>0.05). After intervention for 6 months, the rate of consistent condom use in commercial homosexual activities in the intervention group was 79.5% (101/127), higher than 63.2% (74/117) in the control group, and in the intervention group, 90.1% (73/81) of MSW used condom consistently in heterosexual activities, higher than in the control group (59.6%, 59/99) . Compared with 30.8% (36/117) of MSW with drug abuse history in the control group, a lower proportion of 9.4% (12/127) was observed in the intervention group. Differences in all of aforementioned variables were significant (all P<0.05). After intervention, the incidence of group sex was 3.9% (5/127) in the intervention group and 9.4% (11/117) in the control group, the incidence of anal sex post-alcohol consumption was 40.2% (51/127) in the intervention group and 32.5% (38/117) in control group, the differences were not significant (all P>0.05). Conclusions: The intervention model based on key persons in entertainment venues could promote consistent condom use in MSW in both commercial homosexual and heterosexual activities and help them reduce drug abuse, but had no significant effect on decreasing group sex and anal sex after alcohol consumption. It is crucial to improve the intervention model according to the specific characteristics of MSW in order to enhance the effects of comprehensive intervention.

[The beginnings and evolution of a pancreatic surgeon: a technical morphological analysis in first 5 years]

Objective: To explore the development of the pancreatic surgeon technique in a high-volume center. Methods: A total of 284 cases receiving pancreatic surgery by a single surgeon from June 2015 to December 2020 were retrospectively included in this study. The clinical characteristics and perioperative medical history were extracted from the medical record system of Zhongshan Hospital,Fudan University. Among these patients,there were 140 males and 144 females with an age (M (IQR)) of 61.0 (16.8) years(range: 15 to 85 years). The "back-to-back" pancreatic-jejunal anastomosis procedure was used to anastomose the end of the pancreas stump and the jejunal wall. Thirty days after discharge,the patients were followed by outpatient follow-up or telephone interviews. The difference between categorical variables was analyzed by the Chi-square test or the CMH chi-square test. The statistical differences for the quantitative data were analyzed using one-way analysis of variance or Kruskal-Wallis H test and further analyzed using the LSD test or the Nemenyi test,respectively. Results: Intraoperative blood loss in pancreaticoduodenectomy between 2015 and 2020 were 300,100(100),100(100),100(0),100(200) and 150 (200) ml,respectively. Intraoperative blood loss in distal pancreatectomy was 250 (375),100 (50),50 (65),50 (80),50 (50),and 50 (100) ml,respectively. Intraoperative blood loss did not show statistical differences in the same operative procedure between each year. The operative time for pancreaticoduodenectomy was respectively 4.5,5.0(2.0),5.5(0.8),5.0(1.3),5.0(3.3) and 5.0(1.0) hours in each year from 2015 to 2020,no statistical differences were found between each group. The operating time of the distal pancreatectomy was 3.8 (0.9),3.0 (1.5),3.0 (1.8),2.0 (1.1),2.0 (1.5) and 3.0(2.0) hours in each year,the operating time was obviously shorter in 2018 compared to 2015 (P=0.026) and 2020 (P=0.041). The median hospital stay in 2020 for distal pancreatectomy was 3 days shorter than that in 2019. The overall incidence of postoperative pancreatic fistula gradually decreased,with a incident rate of 50.0%,36.8%,31.0%,25.9%,21.1% and 14.8% in each year. During this period,in a total of 3,6,4,2,0 and 20 cases received laparoscopic operations in each year. The incidence of clinically relevant pancreatic fistula (grade B and C) gradually decreased,the incident rates were 0,4.8%,7.1%,3.4%,4.3% and 1.4%,respectively. Two cases had postoperative abdominal bleeding and received unscheduled reoperation. The overall rate of unscheduled reoperation was 0.7%. A patient died within 30 days after the operation and the overall perioperative mortality was 0.4%. Conclusion: The surgical training of a high-volume center can ensure a high starting point in the initial stage and steady progress of pancreatic surgeons,to ensure the safety of pancreatic surgery.

[High-throughput texture analysis in the distinction of single metastatic brain tumors from high-grade gliomas]

Objective: To explore the feasibility of high-throughput texture analysis in the distinction of single brain metastases (SBM) from high-grade gliomas (HGG) and validate the established model. Methods: A total of 86 patients who were histologically diagnosed with SBM or HGG were retrospectively collected, including 43 patients with SBM and 43 with HGG. All of patients were performed preoperative conventional head magnetic resonance imaging (MRI) scans. A total of 236 fluid-attenuated inversion recovery (FLALR) images containing the information of tumors were selected from the MRI images and each image was considered as an object. The training set had 200 images, including 106 from SBM group and 94 from HGG group, whereas the validation set had 36 images, including 19 from SBM group and 17 from HGG. After images preprocessing, images segmentation, features extraction, and features selection, a radiomic diagnostic model was finally established using the training set. The diagnostic performance of the diagnostic model was evaluated using a receiver operating characteristic (ROC) curve. Hierarchical clustering analysis was used to evaluate the quality of the extracted feature data and the classification effect of the model. The model was further validated using the independent validation set. Results: A total of 629 features were extracted and quantified from each sample, and 41 features were selected to establish feature subsets and the diagnostic model. The classification decision function of the model is f(x)=sign■ and the kernel function of the model is K(x, x(i))=exp■. In the training set, the diagnostic accuracy, sensitivity, specificity, positive predictive value and negative predictive value were 0.845, 0.849, 0.840, 0.857 and 0.832, respectively. The area under the ROC curve reached to 0.939. Similar results were obtained in the validation set. Conclusion: The high-throughput texture analysis shows high accuracy in differentiating SBM from HGG.

[Analysis on voluntary blood donation and associated factors in men who have sex with men in 3 cities in China]

Objective: To assess the prevalence of blood donation and associated factors in men who have sex with men (MSM) in China. Methods: Our observational study was conducted between January and August, 2017 in 3 cities: Guangzhou, Shenzhen and Wuxi. Eligible participants were MSM (≥18 years old) who had either ≥2 male sex partners or unprotected anal sex with casual partners, or had been diagnosed with STI in the past 6 months. A self-completed tablet-based questionnaire was used to collect the information about MSM's socio-demographic characteristics, sexual behaviors and blood donation history. Results: A total of 603 MSM were enrolled in our study, including 302 in Guangzhou, 152 in Shenzhen and 149 in Wuxi, with a mean age of 27.9 years (SD=7.8). Overall, 29.2% (176/603) of the MSM reported a history of blood donation, and 33.1% (100/302)in Guangzhou, 27.6% (42/152) in Shenzhen and 22.8% (34/149) in Wuxi, the differences were not significant (χ(2)=6.421, P=0.093). Multivariate logistic regression analysis indicated that MSM had ever tested for HIV for ≥2 times in the past 12 months (vs. MSM tested for HIV one time, aOR=1.49, 95%CI: 1.08-2.19) or who had ever used gay dating app (vs. MSM who not used gay dating app, aOR=2.13, 95%CI: 1.12-4.44) were more likely to donate blood. Conclusions: Blood donation was common in MSM in China. Health education about blood donation in MSM should be strengthened to ensure the blood safety.

[Clinical value of classified detection of circulating tumor cells in peripheral blood of NSCLC patients]

OBJECTIVE

To investigate the clinical value of detection of circulating tumor cells (CTCs) classified by epithelial cell adhesion molecule (EpCAM) in peripheral blood of patients with non-small cell lung cancer (NSCLC).

METHODS

Peripheral blood samples (7.5 ml each time) were collected from 47 NSCLC patients. Among them, blood samples were collected at the end of each therapy-cycle in three patients for longitudinal monitoring of CTCs. CTCs were enriched by the depletion of leucocytes using a magnetic bead separation technique, stained with EpCAM, cytokeratin 7/8 and their isotypic control antibodies, respectively, and then identified and counted by multi-parameter flow cytometry.

RESULTS

In the blood samples from 47 patients, EpCAM-positive CTCs were detected in 64.3%(9/14), 40.0%(4/10) and 43.5%(10/23) of patients in stages Ⅰ-Ⅱ, Ⅲ and Ⅳ, respectively. EpCAM-negative CTCs were detected in 78.6%(11/14), 90.0%(9/10) and 91.3%(21/23) of patients in stage Ⅰ-Ⅱ, Ⅲ, and Ⅳ, respectively. The total detection rates of EpCAM-positive and EpCAM-negative CTCs were 48.9%(23/47) and 87.2%(41/47), respectively, showing a statistically significant difference between them (P<0.001). According to the stage of the cancer, there was a significant difference between the detection rates of the two types of CTCs in patients of stage Ⅳ(P=0.001), but not in stage Ⅰ-Ⅱ and Ⅲ (P>0.05). The number of EpCAM-negative CTCs was significantly higher than that of EpCAM-positive CTCs in all stages (P<0.05). The frequency of patients with the percentage of EpCAM-negative CTCs >90% was significantly higher in stage Ⅳ patients than that in stage Ⅰ-Ⅱ cases (P=0.030), while the frequency of patients with the percentage of EpCAM-negative CTCs between 50%~90% was significantly lower in the stage Ⅳ than that in the stage Ⅰ-Ⅱ patients (P=0.001). The treatment of most patients with EpCAM-negative CTCs >50% showed to be ineffective (P=0.033).

CONCLUSION

Detection of CTCs classified by EpCAM in peripheral blood is helpful in evaluating the distant metastasis and treatment effectiveness of NSCLC patients.

Seasonal variation and source apportionment of organic tracers in PM10 in Chengdu, China

Organic compound tracers including n-alkanes, triterpane, sterane, polycyclic aromatic hydrocarbons (PAHs) and dicarboxylic acids of airborne particulate matter (PM10) were characterized for samples collected at five sites from July 2010 to March 2011 using GC/MS. Spatial and temporal variations of these organic tracers in PM10 were studied, and their sources were then identified respectively. Average daily concentrations of PM10 varied in different seasons with the trend of PM10 in winter (0.133 mg/m(3)) > autumn (0.120 mg/m(3)) > spring (0.103 mg/m(3)) > summer (0.098 mg/m(3)). Daily concentrations of n-alkanes (C11-C36) ranged from 12.11 to 163.58 ng/m(3) with a mean of 61.99 ng/m(3). The C max and CPI index of n-alkanes indicated that vehicle emissions were the major source in winter, while the contributions of high plant wax emissions became significant in other seasons. It was discovered that the main sources of triterpenoid and steranes were gasoline and diesel engine emissions. Concentrations of ∑15PAHs in PM10 also varied (12.25-58.56 ng/m(3)) in different seasons, and chrysene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(ghi) perylene and fluoranthene were the dominant components. In the four seasons, the concentration of ∑15PAHs was relatively higher at the northern site because of traffic congestion. The main source of airborne PAHs was traffic emissions and coal combustion. Average daily concentrations of dicarboxylic acids (C4-C10) in PM10 ranged from 12.11 to 163.58 ng/m(3), of which azeleic acid was the major compound (0.49-52.04 ng/m(3), average 14.93 ng/m(3)), followed by succinic acid (0.56-19.08 ng/m(3), average 6.84 ng/m(3)). The ratio of C6/C9 showed that the major source in winter was biological, while the contributions of emissions from anthropogenic activities were much higher in summer.

Effects of curcumin on hippocampal expression of NgR and axonal regeneration in Aβ-induced cognitive disorder rats

Curcumin has been widely used for the prevention and treatment of Alzheimer's disease (AD), but its mechanism is still not clear. Inhibitory factors of axonal regeneration have been shown to cause a series of pathophysiological changes in the early period of AD. In this study, the co-receptor (Nogo receptor; NgR) of three axonal growth-inhibitory proteins was examined, and effects of curcumin on spatial learning and memory abilities and hippocampal axonal growth were investigated in amyloid β-protein (Aβ)1-40-induced AD rats. Results showed that the expression of NgR in the AD group significantly increased and the number of axonal protein-positive fibers significantly reduced. The spatial learning and memory abilities of AD rats were significantly improved in the curcumin group. Furthermore, hippocampal expressions of NgR mRNA and protein decreased, and the expression of axonal protein significantly increased. There was a negative correlation between the expression of NgR and axonal growth. Together, these results suggested that curcumin could improve the spatial learning and memory abilities of AD rats. The mechanism might be related with its lowering of hippocampal NgR expression and promoting axonal regeneration.

Isolation and characterization of twenty-one polymorphic microsatellite loci in the Tibetan macaque (Macaca thibetana)

Twenty-one microsatellite loci were isolated from AC-enriched library of Tibetan macaque (Macaca thibetana). The number of alleles at the 21 microsatellite loci ranged from 8 to 15, with an average of 12.2 per locus. Polymorphism information content (PIC) ranged from 0.805 to 0.910 with an average of 0.873. The observed and expected heterozygosities ranged from 0.208 to 0.792 and from 0.843 to 0.938, respectively. These microsatellite loci will be useful for future studies that relate to the genetic diversity and population structure of Tibetan macaque.

Pancreatic cancer cells overexpress gelsolin family-capping proteins, which contribute to their cell motility

BACKGROUND

Previously, proteomic methods were applied to characterise differentially expressed proteins in microdissected pancreatic ductal adenocarcinoma cells.

AIMS

To report that CapG and a related protein, gelsolin, which have established roles in cell motility, are overexpressed in metastatic pancreatic cancer; and to describe their pattern of expression in pancreatic cancer tissue and their effect on cell motility in pancreatic cancer cell lines.

METHODS

CapG was identified by mass spectrometry and immunoblotting. CapG and gelsolin expression was assessed by immunohistochemical analysis on a pancreatic cancer tissue microarray and correlated with clinical and pathological parameters. CapG and gelsolin levels were reduced using RNA interface in Suit-2, Panc-1 and MiaPaCa-2 cells. Cell motility was assessed using modified Boyden chamber or wound-healing assays.

RESULTS

Multiple isoforms of CapG were detected in pancreatic cancer tissue and cell lines. Immunohistochemical analysis of benign (n = 44 patients) and malignant (n = 69) pancreatic ductal cells showed significantly higher CapG staining intensity in nuclear (p<0.001) and cytoplasmic (p<0.001) compartments of malignant cells. Similarly, gelsolin immunostaining of benign (n = 24 patients) and malignant (n = 68 patients) pancreatic ductal cells showed higher expression in both compartments (both p<0.001). High nuclear CapG was associated with increased tumour size (p = 0.001). High nuclear gelsolin was associated with reduced survival (p = 0.01). Reduction of CapG or gelsolin expression in cell lines by RNAi was accompanied by significantly impaired motility.

CONCLUSIONS

Up regulation of these actin-capping proteins in pancreatic cancer and their ability to modulate cell motility in vitro suggest their potentially important role in pancreatic cancer cell motility and consequently dissemination.

Sudden cardiac death associates with a large right atrium thrombus in a late survivor of heart transplantation

A fatal circulatory collapse developed acutely in a patient six years after orthotopic heart transplantation. Autopsy revealed a large, fresh thrombus inside the right atrium which obstructed the orifice of the vena cava completely. The grafted coronary artery and pulmonary vessels were patent. There was no rejection or acute infarct in myocardium. Mildly immature organization was seen on the thrombus-adhered wall. Four chamber enlargement and a rapid decline of right ventricular hypokinesia were detected shortly before death although he did not show active cardiopulmonary symptom. Intracardiac thrombus formation is rather uncommon in late survivor. A synergic effect of atrial turbulence and ventricular hypokinesia in the right heart, superimposed by tissue organization, was proposed for thrombus formation. An empty cardiac output was favored for his mortality. These findings provide a strong evidence to suggest anticoagulation in case of complicated or highly risk of embolization such as turbulence or hypokinesia despite of an absence of active cardiopulmonary symptom.

Gelsolin superfamily proteins: key regulators of cellular functions

Cytoskeletal rearrangement occurs in a variety of cellular processes and involves a wide spectrum of proteins. Among these, the gelsolin superfamily proteins control actin organization by severing filaments, capping filament ends and nucleating actin assembly [1]. Gelsolin is the founding member of this family, which now contains at least another six members: villin, adseverin, capG, advillin, supervillin and flightless I. In addition to their respective role in actin filament remodeling, these proteins have some specific and apparently non-overlapping particular roles in several cellular processes, including cell motility, control of apoptosis and regulation of phagocytosis (summarized in table 1). Evidence suggests that proteins belonging to the gelsolin superfamily may be involved in other processes, including gene expression regulation. This review will focus on some of the known functions of the gelsolin superfamily proteins, thus providing a basis for reflection on other possible and as yet incompletely understood roles for these proteins.

A role for cofilin and LIM kinase in Listeria-induced phagocytosis

The pathogenic bacterium Listeria monocytogenes is able to invade nonphagocytic cells, an essential feature for its pathogenicity. This induced phagocytosis process requires tightly regulated steps of actin polymerization and depolymerization. Here, we investigated how interactions of the invasion protein InlB with mammalian cells control the cytoskeleton during Listeria internalization. By fluorescence microscopy and transfection experiments, we show that the actin-nucleating Arp2/3 complex, the GTPase Rac, LIM kinase (LIMK), and cofilin are key proteins in InlB-induced phagocytosis. Overexpression of LIMK1, which has been shown to phosphorylate and inactivate cofilin, induces accumulation of F-actin beneath entering particles and inhibits internalization. Conversely, inhibition of LIMK's activity by expressing a dominant negative construct, LIMK1(-), or expression of the constitutively active S3A cofilin mutant induces loss of actin filaments at the phagocytic cup and also inhibits phagocytosis. Interestingly, those constructs similarly affect other actin-based phenomenons, such as InlB-induced membrane ruffling or Listeria comet tail formations. Thus, our data provide evidence for a control of phagocytosis by both activation and deactivation of cofilin. We propose a model in which cofilin is involved in the formation and disruption of the phagocytic cup as a result of its local progressive enrichment.

Phosphatidylinositol 4,5-bisphosphate and Arf6-regulated membrane traffic

ADP-ribosylation factor (Arf) 6 regulates the movement of membrane between the plasma membrane (PM) and a nonclathrin-derived endosomal compartment and activates phosphatidylinositol 4-phosphate 5-kinase (PIP 5-kinase), an enzyme that generates phosphatidylinositol 4,5-bisphosphate (PIP2). Here, we show that PIP2 visualized by expressing a fusion protein of the pleckstrin homology domain from PLCdelta and green fluorescent protein (PH-GFP), colocalized with Arf6 at the PM and on tubular endosomal structures. Activation of Arf6 by expression of its exchange factor EFA6 stimulated protrusion formation, the uptake of PM into macropinosomes enriched in PIP2, and recycling of this membrane back to the PM. By contrast, expression of Arf6 Q67L, a GTP hydrolysis-resistant mutant, induced the formation of PIP2-positive actin-coated vacuoles that were unable to recycle membrane back to the PM. PM proteins, such as beta1-integrin, plakoglobin, and major histocompatibility complex class I, that normally traffic through the Arf6 endosomal compartment became trapped in this vacuolar compartment. Overexpression of human PIP 5-kinase alpha mimicked the effects seen with Arf6 Q67L. These results demonstrate that PIP 5-kinase activity and PIP2 turnover controlled by activation and inactivation of Arf6 is critical for trafficking through the Arf6 PM-endosomal recycling pathway.

Stress fiber formation is required for matrix reorganization in a corneal myofibroblast cell line

Corneal wound healing fibroblasts (myofibroblasts) develop a muscle-like contractile apparatus composed of prominent microfilament bundles (stress fibers) and express alpha-smooth muscle actin (alpha-SMA). In this study, gelsolin, an actin filament-severing protein, was overexpressed in a alpha-SMA-expressing corneal myofibroblast cell line (TRK43) to assess whether intact stress fibers are required for in vitro matrix organization and wound contraction. Stably integrated gelsolin was introduced by electroporation of an expression construct (pREPCG8) into cultured cells. Thirty-seven clones were isolated with half of the clones showing a fibroblastic phenotype while the remaining half appeared epithelioid. One fibroblastic clone, GS56, and one epithelioid clone, GS44, were selected for detailed characterization. The GS56 cells appeared highly elongated and spindle-shaped and had prominent stress fibers and focal adhesions. GS44 cells showed disruption of stress fibers and a cortical f-actin organization as well as the down regulation of alpha-SMA expression by immunocytochemistry and Western blotting. Both phenotypes showed enhanced gelsolin expression; however, fractionation of cell extracts demonstrated differences in the subcellular distribution of gelsolin with GS44 cells having markedly reduced and GS56 cells having markedly increased cytoskeletal gelsolin. In an in vitro wound contraction assay, epithelioid GS44 cells showed a significantly impaired ability to contract a collagen matrix compared to that of TRK43 cells, CT9 or GS56 transfectants. Loss of stress fibers in GS44 cells also correlated with enhanced cell motility. Together, these results demonstrate that the ability to form microfilament bundles or stress fibers is required for matrix organization and contraction by corneal myofibroblasts. Although no clear explanation is available, we suspect that differences in gene insertion of the gelsolin overexpression vector may have led to differential intercellular localization of gelsolin and its effect on stress fiber formation in the two cell lines.

[Experimental study on oncogenicity of Aristolochia manshuriensis in rats]

OBJECTIVE

To observe the oncogenetic process, biological behavior, pathological and immunohistochemical features of tumor induced by Aristolochia manshuriensis (AM) in rats.

METHODS

Acute renal injury model was established with AM docoction in different dosages by gastrogavage to observe the histomorphologic and immunohistochemical features dynamically.

RESULTS

(1) At month 0, 1 and 3, the occurrence of renal tumor or tumor-like proliferation was not observed; (2) At month 6, the occurrence of renal tumor-like proliferation in all the three AM dosage groups (50 g/kg, 30 g/kg and 20 g/kg) was 100.0%. Immunohistochemical examination conducted in 2 rats showed that the short spindle-shaped interstitial cells were expressed positively both by vimentin and proliferative cell nuclear antigen (PCNA), but were shown negative for smooth muscle actin (SMA) and p53; (3) At month 6, the occurrence of renal tumor in the three dosage groups was 42.8%, 25.0% and 0% respectively, including 4 cases of renal mesenchymal tumor and 1 case of nephroblastoma. Immunohistochemical examination conducted in 3 cases of renal mesenchymal tumor showed that the short spindle-shaped tumor cells expressed both by vimentin and PCNA, and SMA and p53 were positive for well-differentiated tumor cells. (4) The occurrence of extrarenal tumor in the three dosage groups was 14.3%, 12.5% and 12.5% respectively, 1 case of mammary duct epithelial tumor, 1 thyroid follicle epithelial tumor and 1 skin appendicular epithelial tumor. No tumor occurred in the control group.

CONCLUSION

Large dosage of AM is oncogenic. The occurrence of renal tumor was relatively high, and the histological type is mainly mesenchymal. Vimentin, SMA, PCNA and p53 positive expression was shown for well-differentiated renal mesenchymal tumor. The occurrence of extrarenal tumor is rather low.

Full-contact domain labeling: identification of a novel phosphoinositide binding site on gelsolin that requires the complete protein

Gelsolin, an actin and phosphoinositide binding protein, was photoaffinity labeled using a variety of benzophenone-containing phosphoinositide polyphosphate analogues. The N-terminal half and the C-terminal half of gelsolin showed synergy in the binding of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2]. Competitive displacement experiments with dibutyryl, dioctanoyl, or dipalmitoyl derivatives of PtdIns(4,5)P(2) suggested that, in addition to the inositol headgroup, a diacylglyceryl moiety was important for binding; these analogues also inhibited the gelsolin-severing activity of F-actin. In addition to the previously identified PtdIns(4,5)P2 binding site in the N-terminal half of gelsolin, a new binding site was identified in the C-terminal half by mapping the photocovalently modified peptide fragments. Moreover, increasing concentrations of Ca(2+) decreased the binding of the photolabile analogues to the C-terminal phosphoinositide binding site on gelsolin. A molecular model of the binding of PtdIns(4,5)P2 within two folded repeats of gelsolin has been calculated using these data.

Regulation of apoptosis by phosphatidylinositol 4,5-bisphosphate inhibition of caspases, and caspase inactivation of phosphatidylinositol phosphate 5-kinases

Phosphoinositides such as phosphatidylinositol 3,4,5-trisphosphate and phosphatidylinositol 3,4-bisphosphate promote cell survival and protect against apoptosis by activating Akt/PKB, which phosphorylates components of the apoptotic machinery. We now report that another phosphoinositide, phosphatidylinositol 4,5-bisphosphate (PIP2) is a direct inhibitor of initiator caspases 8 and 9, and their common effector caspase 3. PIP2 inhibited procaspase 9 processing in cell extracts and in a reconstituted procaspase 9/Apaf1 apoptosome system. It inhibited purified caspase 3 and 8 activity, at physiologically attainable PIP2 levels in mixed lipid vesicles. Caspase 3 binding to PIP2 was confirmed by cosedimentation with mixed lipid vesicles. Overexpression of phosphatidylinositol phosphate 5-kinase alpha (PIP5KIalpha), which synthesizes PIP2, suppressed apoptosis, whereas a kinase-deficient mutant did not. Protection by the wild-type PIP5KIalpha was accompanied by decreases in the generation of activated caspases and of caspase 3-cleaved PARP. Protection was not mediated through PIP3 or Akt activation. An anti-apoptotic role for PIP(2) is further substantiated by our finding that PIP5KIalpha was cleaved by caspase 3 during apoptosis, and cleavage inactivated PIP5KIalpha in vitro. Mutation of the P(4) position (D279A) of the PIP5KIalpha caspase 3 cleavage consensus prevented cleavage in vitro, and during apoptosis in vivo. Significantly, the caspase 3-resistant PIP5KIalpha mutant was more effective in suppressing apoptosis than the wild-type kinase. These results show that PIP2 is a direct regulator of apical and effector caspases in the death receptor and mitochondrial pathways, and that PIP5KIalpha inactivation contributes to the progression of apoptosis. This novel feedforward amplification mechanism for maintaining the balance between life and death of a cell works through phosphoinositide regulation of caspases and caspase regulation of phosphoinositide synthesis.

[Immunohistological observation of tonsillae in IgA nephropathy]

OBJECTIVE

To realize the relationship between IgA nephropathy (IgA-N) and immunological abnormality of tonsillae.

METHOD

Thirty-one patients were diagnosed as IgA-N via renal puncture. Sixteen patients suffering from chronic tonsillitis as control. All resected tonsillae were labelled immunohistologically by ABC method.

RESULT

The differences of expression of IgA, IgG in the tonsillae between above two groups were significantly obvious. The number of lymphocytes which can produce IgA increased in IgA-N tonsillae.

CONCLUSION

The immune functions are abnormal in IgA-N patients. Tonsillectomy can prevent the antigen invasion, eliminate IgA originated from tonsillae, decrease the IgA immunocomplex in circulation, therefore decrease the IgA immunocomplex deposition in the basal membrane of glomeruli.

Long-term outcome of acute renal injury induced by Aristolochia manshuriensis Kom in rats

AIM

To investigate the long-term functional and morphological changes of the kidney induced by acute intoxication of Aristolochia manshuriensis Kom in rats.

METHODS

Experimental model of acute renal injury was established in the Sprague-Dawley rats with oral administration of decoctions of Chinese herb, Aristolochia manshuriensis Kom, at dosages of 50 g.kg-1.d-1 and 30 g.kg-1.d-1 for 7 consecutive days, and 20 g.kg-1.d-1 for 15 consecutive days. Renal function was assayed at months 0 (right after treatment), 1, 3, and 6 of the experiment. Renal histological examination was also performed.

RESULTS

1) At month 0, the renal functional changes of acute renal injury included azotemia, low molecular weight proteinuria, glycosuria, hypoosmotic urine, and NAG enzymuria. Histopathological changes showed acute tubular necrosis, predominantly at the corticomedullary junction. 2) At months 1 and 3, the renal function of rats of the experiment was gradually restored and histopathologic examination suggested that the tubular lesions gradually recovered. In HE sections, basophilic deposits were observed in the tubular cytoplasm. And interstitial infiltration of inflammatory cells was not prominent. 3) At months 6, renal preneoplastic lesions, renal tumors, and extrarenal tumors occurred in rats. The occurrence of renal preneoplastic lesions at dosages of 50 g.kg-1.d-1, 30 g.kg-1.d-1, and 20 g.kg-1.d-1 were 100.0% at all three doses, renal tumors 42.8%, 25.0%, and 0%, respectively, extrarenal tumors 14.4%, 12.5%, and 12.5%, respectively, and systemic tumors 57.2%, 37.5%, and 12.5%, respectively. The occurrence of basophilic deposits, renal preneoplastic lesions, renal tumors, and extrarenal tumors in normal control group was nil.

CONCLUSIONS

1) Administration of large dosage of Aristolochia manshuriensis Kom induces acute renal failure in rats. 2) The long-term renal function and histopathologic changes of acute renal injury induced by Aristolochia manshuriensis Komrecover spontaneously. 3) Aristolochia manshuriensis Kom has been proved to be oncogenic for the first time.

Ca2+ regulation of gelsolin by its C-terminal tail

Gelsolin is activated by Ca(2+) to sever actin filaments. Ca(2+) regulation is conferred on the N-terminal half by the C-terminal half. This paper seeks to understand how Ca(2+) regulates gelsolin by testing the "tail helix latch hypothesis," which is based on the structural data showing that gelsolin has a C-terminal tail helix that contacts the N-terminal half in the absence of Ca(2+). Ca(2+) activation of gelsolin at 37 degrees C occurs in three steps, with apparent K(d) for Ca(2+) of 0.1, 0.3, and 6.4 x 10(-6) m. Tail helix truncation decreases the apparent Ca(2+) requirement for severing to 10(-7) m and eliminates the conformational change observed at 10(-6) m Ca(2+). The large decrease in Ca(2+) requirement for severing is not due to a change in Ca(2+) binding nor to Ca(2+)-independent activation of the C-terminal half per se. Thus, the tail helix latch is primarily responsible for transmitting micromolar Ca(2+) information from the gelsolin C-terminal half to the N-terminal half. Occupation of submicromolar Ca(2+)-binding sites primes gelsolin for severing, but gelsolin cannot sever because the tail latch is still engaged. Unlatching the tail helix by 10(-6) m Ca(2+) releases the final constraint to initiate the severing cascade.

Burn-activated neutrophils and tumor necrosis factor-alpha alter endothelial cell actin cytoskeleton and enhance monolayer permeability

BACKGROUND

This study examined the hypothesis that exposure of an endothelial cell (EC) monolayer to tumor necrosis factor-alpha (TNF-alpha) and that burn-activated neutrophils alter EC actin cytoskeleton and enhance the permeability of the monolayer.

METHODS

Neutrophils were harvested from rats that had undergone a 45% surface area burn (BURN-neutrophil) or uninjured control rats. ECs were grown on polyester filters or fibronectin-coated glass slides and exposed for 4 hours to media, TNF-alpha (100 ng/mL), or TNF-alpha plus BURN-neutrophil or uninjured control rats (10(7) cells). Monolayer permeability was assessed by measuring the flux of albumin across the cells. EC surface area and microfilament number and length were determined by the staining of actin microfilaments with rhodamine phalloidin followed by fluorescent microscopy.

RESULTS

The amount of albumin that moved across the monolayer in response to TNF-alpha plus BURN-neutrophil was twice that of media alone (P <.05) or TNF-alpha alone (P <.05). The number and length of actin microfilaments in ECs exposed to TNF-alpha plus BURN-neutrophil were significantly less than that of cells exposed to media alone or TNF-alpha alone.

CONCLUSIONS

These data are consistent with a hypothesis that TNF-alpha plus BURN-neutrophil affect endothelial monolayer permeability by altering EC actin cytoskeletal organization.

Calcium regulation of gelsolin and adseverin: a natural test of the helix latch hypothesis

The gelsolin family of actin filament binding proteins have highly homologous structures. Gelsolin and adseverin, also known as scinderin, are the most similar members of this family, with adseverin lacking a C-terminal helix found in gelsolin. This helix has been postulated to serve as a calcium-sensitive latch, keeping gelsolin inactive. To test this hypothesis, we have analyzed the kinetics of severing by gelsolin, adseverin, and a gelsolin truncate which lacks the C-terminal latch. We find that the relationship between severing rate and calcium ion concentration differs between gelsolin and adseverin, and suggest that calcium controls one rate-limiting step in the activation of adseverin and two in the activation of gelsolin. In contrast, both proteins are activated equally by protons, and have identical severing kinetics at pHs below 6.3. The temperature sensitivity of severing by adseverin and gelsolin is remarkably different, with gelsolin increasing its severing rate 8-fold per 10 degrees C increase in temperature and adseverin increasing its rate only 2-fold per 10 degrees C increase in temperature. Analysis of the gelsolin construct lacking the C-terminal helix demonstrates that this helix is responsible for the regulatory differences between gelsolin and adseverin. These results support the C-terminal latch hypothesis for the calcium ion activation of gelsolin.

Phosphatidylinositol 4,5-bisphosphate induces actin-based movement of raft-enriched vesicles through WASP-Arp2/3

BACKGROUND

Phosphatidylinositol 4,5-bisphosphate (PIP(2)) has been implicated in the regulation of the actin cytoskeleton and vesicle trafficking. It stimulates de novo actin polymerization by activating the pathway involving the Wiskott-Aldrich syndrome protein (WASP) and the actin-related protein complex Arp2/3. Other studies show that actin polymerizes from cholesterol-sphingolipid-rich membrane microdomains called 'rafts', in a manner dependent on tyrosine phosphorylation. Although actin has been implicated in vesicle trafficking, and rafts are sites of active phosphoinositide and tyrosine kinase signaling that mediate apically directed vesicle trafficking, it is not known whether phosphoinositide regulation of actin dynamics occurs in rafts, or if it is linked to vesicle movements.

RESULTS

Overexpression of type I phosphatidylinositol phosphate 5-kinase (PIP5KI), which synthesizes PIP(2), promoted actin polymerization from membrane-bound vesicles to form motile actin comets. Pervanadate (PV), a tyrosine phosphatase inhibitor, induced comets even in the absence of PIP5KI overexpression. PV increased PIP(2) levels, suggesting that it induces comets by changing PIP(2) homeostasis and by increasing tyrosine phosphorylation. Platelet-derived growth factor (PDGF) enhanced PV-induced comet formation, and these stimuli together potentiated the PIP5KI effect. The vesicles at the heads of comets were enriched in PIP5KIs and tyrosine phosphoproteins. WASP-Arp2/3 involvement was established using dominant-negative WASP constructs. Endocytic and exocytic markers identified vesicles enriched in lipid rafts as preferential sites of comet generation. Extraction of cholesterol with methyl-beta-cyclodextrin reduced comets, establishing that rafts promote comet formation.

CONCLUSIONS

Sphingolipid-cholesterol rafts are preferred platforms for membrane-linked actin polymerization. This is mediated by in situ PIP(2) synthesis and tyrosine kinase signaling through the WASP-Arp2/3 pathway. Actin comets may provide a novel mechanism for raft-dependent vesicle transport and apical membrane trafficking.

Domain movement in gelsolin: a calcium-activated switch

The actin-binding protein gelsolin is involved in remodeling the actin cytoskeleton during growth-factor signaling, apoptosis, cytokinesis, and cell movement. Calcium-activated gelsolin severs and caps actin filaments. The 3.4 angstrom x-ray structure of the carboxyl-terminal half of gelsolin (G4-G6) in complex with actin reveals the basis for gelsolin activation. Calcium binding induces a conformational rearrangement in which domain G6 is flipped over and translated by about 40 angstroms relative to G4 and G5. The structural reorganization tears apart the continuous beta sheet core of G4 and G6. This exposes the actin-binding site on G4, enabling severing and capping of actin filaments to proceed.

Plasma gelsolin is reduced in trauma patients

Tissue injury results in the release of the intracellular protein actin which is cleared from the circulation by the plasma proteins gelsolin and Gc-globulin, constituting the Extracellular Actin Scavenger System (EASS). Experimental studies have shown that excessive amounts of actin in the circulation can lead to a condition resembling multiple organ dysfunction syndrome (MODS), and we have previously demonstrated that the level of Gc-globulin is decreased after severe trauma. The purpose of the present study was to determine whether the plasma levels of gelsolin were altered in the early phase after trauma. Twenty-three consecutive trauma patients were studied. Plasma samples were assayed for gelsolin by immunonephelometry with polyclonal rabbit antihuman gelsolin prepared in our own laboratory. The median time from injury until the time the first blood sample was taken was 52 min (range 20-110) and the median Injury Severity Score (ISS) was 20 (range 4-50). The gelsolin level on admission was reduced significantly in the trauma patients compared with normal controls. The median level was 51 mg/L (7-967) vs. 207 mg/L (151-621), P < 0.0001. There was no correlation between admission levels of gelsolin and ISS or survival. This study illustrates that the plasma concentration of gelsolin is significantly diminished immediately after traumatic injury. Further studies are necessary to establish a role for gelsolin or EASS in the development of MODS in trauma patients. The level of serum or plasma gelsolin can be determined rapidly and accurately using a nephelometric assay.

The presentation of serum lipids and uric acid in cerebral ischemia

In this study, we examine the relationship between serum lipids and uric acid in nonembolic cerebral ischemia (NECI) patients. The serum level of total cholesterol (TC) and uric acid increased significantly in male, while TC and triglyceride in female patients. The increase of TC was more significance in female patients. There was no correlation between serum lipids and uric acid in NECI patients or controls, but a significant correlation between triglyceride and uric acid was present in diabetic patient. These findings suggest that lipids and uric acid are essential risk factors for cerebral ischemia in our population. Although there is no association of their metabolism, their parallellic abnormality in diabetic NECI individuals indicates that some possible factors changing in diabetics can influence the metabolic pathway of both lipid and uric acid, which may promote each other for atherogenesis in diabetics.

Phosphoinositide 3-kinase in rat liver nuclei

Biochemical and immunochemical data from the present investigation reveal the existence of a p85/p110 phosphoinositide 3-kinase (PI 3-kinase) in rat liver nuclei. 32P-Labeling of membrane phosphoinositides by incubating intact nuclei with [gamma-32P]ATP results in the formation of [32P]phosphatidyl-inositol 3,4, 5-trisphosphate [PtdIns(3,4,5)P3], accompanied by small quantities of [32P]phosphatidylinositol 3-phosphate [PtdIns(3)P]. Studies with subnuclear fractions indicate that the PI 3-kinase is not confined to nuclear membranes. The nuclear soluble fraction also contains PI 3-kinase and an array of inositide-metabolizing enzymes, including phospholipase C (PLC), phosphoinositide phosphatase, and diacylglycerol (DAG) kinase. As a result, exposure of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] to the nuclear extract in the presence of [gamma-32P]ATP generates a series of 32P-labeled D-3 phosphoinositides and phosphatidic acid (PA) in an interdependent manner. On the basis of the immunological reactivity and kinetic behavior, the nuclear PI 3-kinase is analogous, if not identical, to PI 3-kinase alpha, and constitutes about 5% of the total PI 3-kinase in the cell. Moreover, we test the premise that nuclear PI 3-kinase may, in part, be regulated through the control of substrate availability by PtdIns(4,5)P2-binding proteins. Effect of CapG, a nuclear actin-regulatory protein, on PI 3-kinase activity is examined in view of its unique Ca2+-dependent PtdIns(4, 5)P2-binding capability. In vitro data show that the CapG-mediated inhibition of nuclear PI 3-kinase is prompted by PKC phosphorylation of CapG and elevated [Ca2+]. This CapG-dependent regulation provides a plausible link between nuclear PLC and PI 3-kinase pathways for cross-communications. Taken together, these findings provide definite data concerning the presence of an autonomous PI 3-kinase cycle in rat liver nuclei. The nuclear location of PI 3-kinase may lead to a better understanding regarding its functional role in transducing signals from the plasma membrane to the nucleus in response to diverse physiological stimuli.

Identification of the binding partners for flightless I, A novel protein bridging the leucine-rich repeat and the gelsolin superfamilies

Flightless-I (fliI) is a novel member of the gelsolin family that is important for actin organization during Drosophila embryogenesis and myogenesis. Drosophila fliI and the human homolog FLI both contain the classic gelsolin 6-fold segmental repeats and an amino-terminal extension of 16 tandem leucine-rich repeats (LRR). LRR repeats form amphipathic beta-alpha structural units that mediate protein-protein interactions. Although there are close to 100 known LRR domain-containing proteins, only a few binding pairs have been identified. In this paper, we used biochemical and genetic approaches to identify proteins that interact with human FLI. In vitro synthesized FLI bound to actin-Sepharose and binding was reduced by competition with excess soluble actin. Actin binding was mediated through the gelsolin-like domain and not the LRR domain. Although the FLI LRR module is most closely related to the LRR domains of Ras-interactive proteins, FLI does not associate with Ras, selected Ras effectors, or other Ras-related small GTPases. Two-hybrid screens using FLI LRR as bait identified a novel LRR binding partner. The 0.65-kilobase pair (kb) clone from the screen survived additional rounds of stringent two-hybrid pairwise assays, establishing a specific interaction. Binding to FLI LRR was corroborated by co-immunoprecipitation with FLI LRR. The translated sequence of the FLI LRR associated protein (FLAP) encodes a novel protein not represented in the data base. Northern blot analyses revealed four FLAP messages of approximately 2.7, 2.9, 3.3, and 5.1 kb, which are differentially expressed in the tissues tested. Skeletal and cardiac muscles are particularly rich in the 3.3-kb FLAP message, and the FLI message as well. Full-length FLAP clones were isolated from a mouse skeletal muscle cDNA library. They have an open reading frame which encodes for a protein containing 626 amino acids. Sequence analyses predict that the FLAP protein is rich in alpha-helices and contains stretches of dimeric coiled coil in its middle region and COOH terminus. The identification of actin and FLAP as the binding ligands for the gelsolin-like domain and the LRR domain, respectively, suggests that FLI may link the actin cytoskeleton to other modules implicated in intermolecular recognition and structural organization.

Successful resection of a teratoma of the third ventricle in a 3-year-old boy

Few cases of teratoma in the third ventricle have been reported in detail. We describe a 3-year-old Chinese boy presenting with increased intracranial pressure, headache, and vomiting. Preoperative computed tomography and magnetic resonance imaging demonstrated a teratoma in the third ventricle. Complete excision of the tumor was achieved through the interhemispheric transcallosal approach. The patient did well and was without neurologic deficits postoperatively. Although the majority of tumors located in the third ventricle are malignant and can penetrate the brain tissues that constitute the wall of the third ventricle, mature teratomas are an exception and total removal may be possible.

Synergistic activation of dynamin GTPase by Grb2 and phosphoinositides

Hydrolysis of GTP by dynamin is essential for budding clathrin-coated vesicles from the plasma membrane. Two distinct domains of dynamin are implicated in the interactions with dynamin GTPase activators. Microtubules and Grb2 bind to the carboxyl-terminal proline/arginine-rich domain (PRD), whereas phosphoinositides bind to the pleckstrin homology (PH) domain. In this study we tested the effect of different phosphoinositides on dynamin GTPase activity and found that the best activator is phosphatidylinositol 4,5-bisphosphate followed by 1-O-(1, 2-di-O-palmitoyl-sn-glycerol-3-benzyloxyphosphoryl)-D-myo-inositol 3,4,5-triphosphate. Phosphatidylinositol 4-phosphate was a weak activator and phosphatidylinositol 3,4-bisphosphate did not activate GTPase at all. We then addressed the question of whether both domains of dynamin, PRD and PH, can be engaged simultaneously, and determined the effects of dual occupancy on dynamin GTPase activity. We found that Grb2 and phosphatidylinositol 4,5-bisphosphate together increased the dynamin GTPase activity up to 4-fold higher than that obtained by these activators tested separately, and also reduced the dynamin concentration required for half-maximal activities by 3-fold. These results indicate that both stimulators can bind to dynamin simultaneously resulting in superactivation of dynamin GTPase activity. We propose that SH3-containing proteins such as Grb2 bind to the dynamin PRD to target it to clathrin-coated pits and prime it for superactivation by phosphoinositides.

Cavernous sinus syndrome and hepatoma metastasis

A 46-year-old man presented with left cavernous sinus syndrome and subsequent right leg pain proved clear cell type hepatocellular carcinoma metastasis. An initial liver function test was normal and alpha-fetoprotein was only 15 ng/ml but they increased rapidly and he progressed to hepatic failure 2 weeks later. Therefore, a subclinical hepatoma with metastasis should be differentiated in cavernous sinus syndrome, even in cases of normal hepatic enzymes, because hepatoma is prevalent in Taiwan.

Antiplatelet drugs induce apoptosis in cultured cancer cells

In order to understand if antiplatelet drugs possess direct antineoplastic property, we tested the apoptotic effect of 5 popularly marketed antiplatelet drugs in Taiwan in 6 cultured cancer cell lines (Hep 3B hepatocarcinoma, U87-MG malignant glioma, PC-3 prostate adenocarcinoma, HeLa cervical adenocarcinoma, HL-60 preleukemia and K-562 chronic myelogenous leukemia). While acetylsalicylate and flunarizine exerted no effect on these cancer cells, pentoxifyline (PTX), dipyridamole (DYA) and ticlopidine hydrochloride (T. HCl) displayed a time and dose-dependent apoptotic effect on them except for HL-60 and K-562 cells. PTX induced apoptosis in U87-MG, Hep 3B and HeLa cells, DYA in HeLa cells, while T. HCl in U87-MG, Hep 3B, PC-3 and HeLa cells. Adriamycin also provoked apoptotic effect in all 6 cell lines but neither PTX, DYA nor T. HCl acted synergy with adriamycin to HeLa cells, implicating that they may share a similar pathway for inducing apoptosis. Therefore, our results show that the antiplatelet drugs do possess antineoplastic property in vitro. A co-administration of antiplatelet drugs is noteworthy for an alternative adjunctive therapy in cancer patients.

Gelsolin modulates phospholipase C activity in vivo through phospholipid binding

Gelsolin and CapG are actin regulatory proteins that remodel the cytoskeleton in response to phosphatidylinositol 4,5-bisphosphate (PIP2) and Ca2+ during agonist stimulation. A physiologically relevant rise in Ca2+ increases their affinity for PIP2 and can promote significant interactions with PIP2 in activated cells. This may impact divergent PIP2- dependent signaling processes at the level of substrate availability. We found that CapG overexpression enhances PDGF-stimulated phospholipase Cgamma (PLCgamma) activity (Sun, H.-q., K. Kwiatkowska, D.C. Wooten, and H.L. Yin. 1995. J. Cell Biol. 129:147-156). In this paper, we examined the ability of gelsolin and CapG to compete with another PLC for PIP2 in live cells, in semiintact cells, and in vitro. We found that CapG and gelsolin overexpression profoundly inhibited bradykinin-stimulated PLCbeta. Inhibition occurred at or after the G protein activation step because overexpression also reduced the response to direct G protein activation with NaF. Bradykinin responsiveness was restored after cytosolic proteins, including gelsolin, leaked out of the overexpressing cells. Conversely, exogenous gelsolin added to permeabilized cells inhibited response in a dose-dependent manner. The washout and addback experiments clearly establish that excess gelsolin is the primary cause of PLC inhibition in cells. In vitro experiments showed that gelsolin and CapG stimulated as well as inhibited PLCbeta, and only gelsolin domains containing PIP2-binding sites were effective. Inhibition was mitigated by increasing PIP2 concentration in a manner consistent with competition between gelsolin and PLCbeta for PIP2. Gelsolin and CapG also had biphasic effects on tyrosine kinase- phosphorylated PLCgamma, although they inhibited PLCgamma less than PLCbeta. Our findings indicate that as PIP2 level and availability change during signaling, cross talk between PIP2-regulated proteins provides a selective mechanism for positive as well as negative regulation of the signal transduction cascade.

Gelsolin binding to phosphatidylinositol 4,5-bisphosphate is modulated by calcium and pH

The actin cytoskeleton of nonmuscle cells undergoes extensive remodeling during agonist stimulation. Lamellipodial extension is initiated by uncapping of actin nuclei at the cortical cytoplasm to allow filament elongation. Many actin filament capping proteins are regulated by phosphatidylinositol 4,5-bisphosphate (PIP2), which is hydrolyzed by phospholipase C. It is hypothesized that PIP2 dissociates capping proteins from filament ends to promote actin assembly. However, since actin polymerization often occurs at a time when PIP2 concentration is decreased rather than increased, capping protein interactions with PIP2 may not be regulated solely by the bulk PIP2 concentration. We present evidence that PIP2 binding to the gelsolin family of capping proteins is enhanced by Ca2+. Binding was examined by equilibrium and nonequilibrium gel filtration and by monitoring intrinsic tryptophan fluorescence. Gelsolin and CapG affinity for PIP2 were increased 8- and 4-fold, respectively, by microM Ca2+, and the Ca2+ requirement was reduced by lowering the pH from 7.5 to 7.0. Studies with the NH2- and COOH-terminal halves of gelsolin showed that PIP2 binding occurred primarily at the NH2-terminal half, and Ca2+ exposed its PIP2 binding sites through a change in the COOH-terminal half. Mild acidification promotes PIP2 binding by directly affecting the NH2-terminal sites. Our findings can explain increased PIP2-induced uncapping even as the PIP2 concentration drops during cell activation. The change in gelsolin family PIP2 binding affinity during cell activation can impact divergent PIP2-dependent processes by altering PIP2 availability. Cross-talk between these proteins provides a multilayered mechanism for positive and negative modulation of signal transduction from the plasma membrane to the cytoskeleton.

The actin cytoskeleton is required for receptor-mediated endocytosis in mammalian cells

Actin filament organization is essential for endocytosis in yeast. In contrast, the actin-depolymerizing agent cytochalasin D has yielded ambiguous results as to a role for actin in receptor-mediated endocytosis in mammalian cells. We have therefore re-examined this issue using highly specific reagents known to sequester actin monomers. Two of these reagents, thymosin beta4 and DNase I, potently inhibited the sequestration of transferrin receptors into coated pits as measured in a cell-free system using perforated A431 cells. At low concentrations, thymosin beta4 but not DNase I was stimulatory. Importantly, the effects of both reagents were specifically neutralized by the addition of actin monomers. A role for the actin cytoskeleton was also detected in intact cells where latrunculin A, a drug that sequesters actin monomers, inhibited receptor-mediated endocytosis. Biochemical and morphological analyses suggest that these reagents inhibit later events in coated vesicle budding. These results provide new evidence that the actin cytoskeleton is required for receptor-mediated endocytosis in mammalian cells.

Prediction of total cholesterol: high-density-lipoprotein-cholesterol ratio in young adults

Abnormal cholesterol fraction is an essential risk factor for atherosclerosis of large cerebral arteries in young Asians. In order to reduce the medical cost and social resource for cholesterol electrophoresis, especially in undeveloped and developing Asian countries, we evaluated the validity of Nanji's GUT score for predicting TC: HDLC ratio in this population. Results showed that GUT score only predicted 71% of them. We also tested the predictive power of CUT index, and predicting rate was 81%. Therefore, Nanji's GUT score is not an ideal surrogate for cholesterol electrophoresis. We recommend CUT index to screen for high-risk subjects till a new method can satisfy the economic pattern in Asian countries.

Decreased plasma gelsolin concentrations in acute liver failure, myocardial infarction, septic shock, and myonecrosis

OBJECTIVE

To quantitate gelsolin concentrations in serum of patients with a variety of conditions involving actin release into the circulation.

DESIGN

Prospective evaluation of sera on consecutive patients.

SETTING

Metropolitan county hospital.

PATIENTS

Ninety hospital patients with a variety of well-characterized diseases.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Sera were studied from patients with acute liver failure (n = 18), chronic hepatitis (n = 17), cirrhosis of varying etiology (n = 17), pancreatitis (n = 10), acute myocardial infarction (n = 10), myonecrosis due either to polymyositis or crush injuries (n = 12), and septic shock (n = 6); results were compared with sera from healthy individuals (n = 25). Gelsolin was quantified by Western blotting with monoclonal anti-gelsolin and laser densitometry. Significant reductions in mean gelsolin concentrations compared with healthy controls were observed in patients with acute liver failure (47%), myocardial infarction (69%), sepsis (51%), and myonecrosis (66%). An inverse correlation was observed between gelsolin concentration and severity of illness, as indicated by the magnitude of serum enzyme concentrations.

CONCLUSIONS

Gelsolin depletion occurs in a variety of tissue injury syndromes. Depletion of actin-scavenger capacity in the presence of continued actin release may affect outcome in situations of severe organ damage.

Lipid products of phosphoinositide 3-kinase bind human profilin with high affinity

To gain insight into the physiological function of phosphoinositide 3-kinase (PI 3-kinase) lipid products, this study examines the interactions of the D-3 phosphoinositides with profilin and the consequent effects on actin dynamics and phosphoinositide turnover. Profilin, a ubiquitous actin-regulating protein, plays a putative role in regulating actin assembly and PLC-gamma 1 signaling in light of its unique interactions with actin and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2]. Here we raise evidence that the affinity of profilin with the D-3 phosphoinositides is substantially higher than that of PtdIns(4,5)P2. The dissociation constants (Kd) are estimated to be 1.1 microM, 5.7 microM, and 11 microM for phosphatidylinositol 3,4-bisphosphate [PtdIns(3,4)P2], phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P3], and PtdIns(4,5)P2, respectively. Spectroscopic data show that while all these phosphoinositides alter the tryptophan fluorescence of profilin in a similar fashion, the respective conformational effect on profilin is vastly different. Based on CD data, the alpha-helical contents of profilin in the presence of 8 molar equiv of PtdIns(4,5)P2, PtdIns(3,4,5)P3, and PtdIns(3,4)P2 are 17.4%, 11.5%, and 1.4%, respectively, vis-a-vis 9.4% for profilin alone. In contrast, no appreciable change in the fluorescence and CD spectra is observed when related inositol phosphates such as Ins(1,4,5)P3, Ins(1,3,4,5)P4, or Ins(1,3,4)P3 at comparable concentrations are tested. Evidence suggests that this differential recognition bears functional significance concerning the intricate roles of profilin and inositol lipids in modulating actin polymerization and PtdIns(4,5)P2 turnover. The relative potency of individual phosphoinositides in offsetting the inhibitory effect of profilin on actin assembly is PtdIns(3,4)P2 > PtdIns(3,4,5)P3 > PtdIns(4,5)P2, consistent with their relative binding affinity with profilin. Moreover, the inhibitory effect of profilin on PLC-gamma 1-mediated PtdIns(4,5)P2 hydrolysis is overcome by PtdIns(3,4)P2 and PtdIns(3,4,5)P3 through a combined effect of PLC-gamma 1 activation and preferential profilin binding. This D-3 phosphoinositide-mediated regulation may represent a new mechanism for controlling PtdIns(4,5)P2 turnover by PLC-gamma 1.

beta-Thymosins are not simple actin monomer buffering proteins. Insights from overexpression studies

beta-Thymosins are the currently favored candidates for maintaining the large actin monomer (G-actin) pool in living cells. To determine if beta-thymosin behaves like a simple G-actin buffering agent in the complex environment of a cell, we overexpressed thymosin beta10 (Tbeta 10) in NIH3T3 cells and determined the effect on the monomer/polymer equilibrium. Tbeta 10 is the predominant beta-thymosin isoform in the NIH3T3 cell line, and it is present in approximately equal molar ratio to profilin and cofilin/actin depolymerizing factor, two other well characterized actin monomer binding proteins. Clonal cell lines that overexpressed three times more Tbeta 10 had 23-33% more polymerized actin than control cells, and the filaments appeared thicker after staining with fluorescent phalloidin. There was no change in total actin, profilin, and cofilin/actin depolymerizing factor content. The overexpressing cells were more motile; they spread faster and had higher chemotactic and wound healing activity. Assuming that there is no compensatory inactivation of the other classes of monomer binding proteins, our paradoxical observation can be accounted for quantitatively by a parallel in vitro study (Carlier, M.-F., Didry, D., Erk, I., Lepault, J., Van Troys, L., Vanderkekove, J., Perelroizen, I., Yin, H. L., Doi, Y., and Pantaloni, D., (1996) J. Biol. Chem. 271, 9231-9239). beta-Thymosin at levels comparable with that found in the overexpressing cells binds actin filaments and decreases the critical concentration (C(c)) for actin polymerization. This reduces the monomer buffering ability of beta-thymosin, so that above a certain threshold an incremental increase in thymosin does not lead to a corresponding increase in G-actin. Furthermore, the decrease in C(c) reduces the buffering capacity of the other actin monomer binding proteins. As a consequence, an increase in beta-thymosin does not necessarily result in a proportionate increase in actin monomer content in a complex environment containing other actin monomer binding proteins. The outcome depends on the level of beta-thymosin expression relative to the composition of the other actin monomer binding protein. Our results suggest that beta-thymosins are not simple actin buffering proteins and that their biphasic action may have physiological significance.

The mouse thymosin beta 4 gene: structure, promoter identification, and chromosome localization

Thymosin beta 4 (T beta 4) is an actin monomer sequestering protein that may have a critical role in modulating the dynamics of actin polymerization and depolymerization in nonmuscle cells. Its regulatory role is consistent with the many examples of transcriptional regulation of T beta 4 and of tissue-specific expression. Furthermore, lymphocytes have a unique T beta 4 transcript relative to the ubiquitous transcript found in many other tissues and cells. To determine how T beta 4 gene expression is regulated and how the alternative transcripts are derived, we cloned the mouse T beta 4 gene. We established that there is a single mouse T beta 4 gene and found that the lymphoid-specific transcript is generated by extending the ubiquitous exon 1 with an alternate downstream splice site. The transcription start site is defined by primer extension analysis, and the 5'-flanking region has many of the characteristics of a promoter. It is pyrimidine-rich and contains typical promoter elements, including a GC box, an initiator site, and consensus transcription factor binding sites. The mouse T beta 4 gene locus (Ptmb4) is located by interspecific backcross mapping to the distal region of the mouse X chromosome, linked to Btk and Gja6.

Identification of two sites in gelsolin with different sensitivities to adenine nucleotides

The affinity of monomeric actin for several actin-binding proteins, including gelsolin, depends on adenine nucleotides. Gelsolin binds faster and with higher affinity to ADP-actin than to ATP-actin. Here, we show that the C-terminal actin-binding domain of gelsolin, which is required for filament nucleating activity but not for filament severing activity, contains the site that distinguishes between ATP-actin and ADP-actin monomers. In contrast, actin binding to the N-terminal half of gelsolin depends on solution ATP concentrations, but not on the nucleotide (ATP or ADP) tightly bound in the cleft of the actin monomer. Binding is stronger in the absence of free nucleotide or in the presence of 0.5 mM ADP than in solutions containing 0.5 mM ATP. Complexes formed using different nucleotide concentrations differ in their filament-severing activities as well as in their abilities to increase the fluorescence of 4-chloro-7-nitrobenzeno-2-oxa-1,3-diazole-labeled actin monomers. These results suggest that, at physiologic concentrations of nucleotides, both free and actin-bound ATP may affect the binding of actin to its accessory proteins and that gelsolin, actin, or the gelsolin-actin complex, contains a low-affinity nucleotide-binding site.

Bilateral cheiro-oral syndrome and traumatic subdural hematoma

Typical bilateral cheiro-oral syndrome was encountered in a 74-year-old man who had bilateral subdural hematoma after a minor head injury. The delayed grave neurologic deficits occurred 1 month later without expansion of the hematoma. Removal of the lesions reversed both cheiro-oral syndrome and his late-onset neurological disabilities.

Effects of CapG overexpression on agonist-induced motility and second messenger generation

Actin modulating proteins that bind polyphosphoinositides, such as phosphatidylinositol 4, 5-bisphosphate (PIP2), can potentially participate in receptor signaling by restructuring the membrane cytoskeleton and modulating second messenger generation through the phosphoinositide cycle. We examined these possibilities by overexpressing CapG, an actin filament end capping, Ca(2+)- and polyphosphoinositide-binding protein of the gelsolin family. High level transient overexpression decreased actin filament staining in the center of the cells but not in the cell periphery. Moderate overexpression in clonally selected cell lines did not have a detectible effect on actin filament content or organization. Nevertheless, it promoted a dose-dependent increase in rates of wound healing and chemotaxis. The motile phenotype was similar to that observed with gelsolin overexpression, which in addition to capping, also severs and nucleates actin filaments. CapG overexpressing clones are more responsive to platelet-derived growth factor than control-transfected clones. They form more circular dorsal membrane ruffles, have higher phosphoinositide turnover, inositol 1,4,5-trisphosphate generation and Ca2+ signaling. These responses are consistent with enhanced PLC gamma activity. Direct measurements of PIP2 mass showed that the CapG effect on PLC gamma was not due primarily to an increase in the PIP2 substrate concentration. The observed changes in cell motility and membrane signaling are consistent with the hypothesis that PIP(2)-binding actin regulatory proteins modulate phosphoinositide turnover and second messenger generation in vivo. We infer that CapG and related proteins are poised to coordinate membrane signaling with actin filament dynamics following cell stimulation.

Actin filament disassembly is a sufficient final trigger for exocytosis in nonexcitable cells

Although the actin cytoskeleton has been implicated in vesicle trafficking, docking and fusion, its site of action and relation to the Ca(2+)-mediated activation of the docking and fusion machinery have not been elucidated. In this study, we examined the role of actin filaments in regulated exocytosis by introducing highly specific actin monomer-binding proteins, the beta-thymosins or a gelsolin fragment, into streptolysin O-permeabilized pancreatic acinar cells. These proteins had stimulatory and inhibitory effects. Low concentrations elicited rapid and robust exocytosis with a profile comparable to the initial phase of regulated exocytosis, but without raising [Ca2+], and even when [Ca2+] was clamped at low levels by EGTA. No additional cofactors were required. Direct visualization and quantitation of actin filaments showed that beta-thymosin, like agonists, induced actin depolymerization at the apical membrane where exocytosis occurs. Blocking actin depolymerization by phalloidin or neutralizing beta-thymosin by complexing with exogenous actin prevented exocytosis. These findings show that the cortical actin network acts as a dominant negative clamp which blocks constitutive exocytosis. In addition, actin filaments also have a positive role. High concentrations of the actin depolymerizing proteins inhibited all phases of exocytosis. The inhibition overrides stimulation by agonists and all downstream effectors tested, suggesting that exocytosis cannot occur without a minimal actin cytoskeletal structure.

Actin monomer binding proteins

Small actin monomer binding proteins are essential components of the actin polymerization machinery. Originally thought of as passive buffers that prevent polymerization of actin monomers, recent discoveries elucidate how some actin monomer binding proteins can promote as well as inhibit polymerization, and how they cooperate to regulate actin assembly.

The actin side-binding domain of gelsolin also caps actin filaments. Implications for actin filament severing

Gelsolin is an actin filament-severing and -capping protein which is inhibited by polyphosphoinositides (PPI). Severing requires gelsolin binding to the side of the filaments through a site in segments 2 and 3 (S2-3) to position another site in segment 1 (S1) to sever filaments. In this paper, we report that S2-3, like S1, caps actin filaments. Since neither S1 and S2-3 caps as well as gelsolin, and neither severs actin filament, S2-3 may actively contribute to severing by capping filaments cooperatively with S1. We used deletional mutagenesis to locate the S2-3 sequence required for actin filament side binding, capping, and PPI binding and found that these sites are located close to the NH2 terminus of S2 (residues 161-172). S3, a segment which has no known function up to now and does not by itself bind actin, contributes to stable capping and may contain an additional PPI-binding site.