The effect of the nucleolar protein ZNF385A on the ribosomal DNA copy number variation in response to Cr(VI)-induced DNA damage.

Hexavalent chromium [Cr(VI)] is a widely distributed carcinogen in industrial contexts and general environmental contexts. Emerging research highlights the central role of ribosomal DNA (rDNA) in DNA Damage Responses (DDRs). However, there remains a lack of investigation into the potential dose-dependent relationship between exposure to Cr(VI) and alterations in rDNA copy number (CN), as well as the related mechanisms underlying these effects. A molecular epidemiological investigation involving 67 workers exposed to Cr(VI) and 75 unexposed controls was conducted. There was a notable increase in ZNF385A expression, variations in rDNA CN, and elevated γH2AX levels in the peripheral blood of Cr(VI)-exposed workers. Restricted cubic spline (RCS) models showed that blood Cr levels in the exposed population exhibited non-linear dose-dependent relationships with γH2AX, rDNA CN, and ZNF385A. Of considerable interest, there were robust and positive associations between ZNF385A and both γH2AX and rDNA CN. Further in vitro experiments provided concrete evidence that Cr(VI) simultaneously caused an increase in ZNF385A expression and variations in rDNA CN. ZNF385A-depleted cells showed increased sensitivity to Cr(VI)-mediated DDRs and alterations in rDNA CN. This study indicated that ZNF385A played a highly significant role in the rDNA CN variation in response to Cr(VI)-induced DNA damage.

α-(N-Alkyl-N-heteroarenium)-α-diazoacetates: synthesis and reactivity of a novel class of 'onium' diazo compounds.

Treatment of alkyl α-(N-heteroaryl)-α-diazoacetates with alkylating reagents affords diazoacetate N-heteroarenium salts. These novel 'onium' diazo compounds are mostly yellow solids, displaying increased thermal and acid stability. Their tetrafluoroborates undergo rhodium catalyzed [2 + 1] and Doyle-Kirmse reactions under mild conditions, suggesting the N-quaternization an effective means of elimination of N-coordination caused catalyst toxicity.

Sulfur-based fluorescent probes for biological analysis: A review.

The widespread adoption of small-molecule fluorescence detection methodologies in scientific research and industrial contexts can be ascribed to their inherent merits, including elevated sensitivity, exceptional selectivity, real-time detection capabilities, and non-destructive characteristics. In recent years, there has been a growing focus on small-molecule fluorescent probes engineered with sulfur elements, aiming to detect a diverse array of biologically active species. This review presents a comprehensive survey of sulfur-based fluorescent probes published from 2017 to 2023. The diverse repertoire of recognition sites, including but not limited to N, N-dimethylthiocarbamyl, disulfides, thioether, sulfonyls and sulfoxides, thiourea, thioester, thioacetal and thioketal, sulfhydryl, phenothiazine, thioamide, and others, inherent in these sulfur-based probes markedly amplifies their capacity for detecting a broad spectrum of analytes, such as metal ions, reactive oxygen species, reactive sulfur species, reactive nitrogen species, proteins, and beyond. Owing to the individual disparities in the molecular structures of the probes, analogous recognition units may be employed to discern diverse substrates. Subsequent to this classification, the review provides a concise summary and introduction to the design and biological applications of these probe molecules. Lastly, drawing upon a synthesis of published works, the review engages in a discussion regarding the merits and drawbacks of these fluorescent probes, offering guidance for future endeavors.

Cr (VI)-induced ribosomal DNA copy number variation is associated with semen quality impairment: Evidence from human to animal study.

OBJECTIVES: This study aimed to analyze the possible role of rDNA copy number variation in the association between hexavalent chromium [Cr (VI)] exposure and semen quality in semen donors and further confirm this association in mice. METHODS: In this cross-sectional study, whole blood and semen samples were collected from 155 semen donors in the Zhejiang Human Sperm Bank from January 1st to April 31st, 2021. Adult C57BL/6 J male mice were treated with different doses of Cr (VI) (0, 10, or 15 mg/kg b.w./day). Semen quality, including semen volume, total spermatozoa count, sperm concentration, progressive motility, and total motility, were analyzed according to the WHO laboratory manual. Cr concentration was detected using inductively coupled plasma mass spectrometry. The rDNA copy number was measured using qPCR. RESULTS: In semen donors, whole blood Cr concentration was negatively associated with semen concentration and total sperm counts. Semen 5 S and 45 S rDNA copy numbers were negatively associated with whole blood Cr concentration and whole blood 5.8 S rDNA copy number was negatively associated with semen Cr concentration. In mice, Cr (VI) damaged testicular tissue, decreased semen quality, and caused rDNA copy number variation. Semen quality was related to the rDNA copy number in whole blood, testicular tissue, and semen samples in mice. CONCLUSION: Cr (VI) was associated with decreased semen quality in semen donors and mice. Our findings suggest an in-depth analysis of the role of the rDNA copy number variation in the Cr (VI)-induced impairment of semen quality.

Pinpointing Moisture: The Capacitive Detection for Standing Tree Health.

BACKGROUND: the feasibility of the capacitance method for detecting the water content in standing tree trunks was investigated using capacitance-based equipment that was designed for measuring the water content of standing tree trunks. METHODS: In laboratory experiments, the best insertion depth of the probe for standing wood was determined by measurement experiments conducted at various depths. The bark was to be peeled when specimens and standing wood were being measured. The actual water content of the test object was obtained by specimens being weighed and the standing wood being weighed after the wood core was extracted. RESULTS: A forecast of the moisture content of standing wood within a range of 0 to 180% was achieved by the measuring instrument. The feasibility of the device for basswood and fir trees is preliminarily studied. When compared to the drying method, the average error of the test results was found to be less than 8%, with basswood at 7.75%, and fir at 7.35%. CONCLUSIONS: It was concluded that the measuring instrument has a wide measuring range and is suitable for measuring wood with low moisture content, as well as standing timber with high moisture content. The measuring instrument, being small in size, easy to carry, and capable of switching modes, is considered to have a good application prospect in the field of forest precision monitoring and quality improvement.

STED Imaging of Vesicular Endocytosis in the Synapse.

Endocytosis is a fundamental biological process that couples exocytosis to maintain the homeostasis of the plasma membrane and sustained neurotransmission. Super-resolution microscopy enables optical imaging of exocytosis and endocytosis in live cells and makes an essential contribution to understanding molecular mechanisms of endocytosis in neuronal somata and other types of cells. However, visualization of exo-endocytic events at the single vesicular level in a synapse with optical imaging remains a great challenge to reveal mechanisms governing the synaptic exo-endocytotic coupling. In this protocol, we describe the technical details of stimulated emission depletion (STED) imaging of synaptic endocytosis at the single-vesicle level, from sample preparation and microscopy calibration to data acquisition and analysis.

Exosomal proteomics and cytokine analysis distinguish silicosis cases from controls.

Occupational silica exposure caused a serious disease burden of silicosis. There is currently a lack of sensitive and effective biomarkers for silicosis, and the pathogenesis of silicosis is unclear. Exosomes were significant in the pathogenesis of silicosis, and our study was carried out from exosomal proteomics and cytokine analysis. Firstly, the plasma levels of cytokines were detected using a Luminex multiplex assay, and the results indicated that the plasma levels of TNF-α, IL-6, CCL2, CXCL10, and PDGF-AB were significantly higher in silicosis patients than in silica-exposed workers and controls (p < 0.05). After correlation analysis, the plasma levels of cytokines were positively correlated with exosomal protein concentration. Secondly, data-independent acquisition (DIA) was performed on plasma-derived exosomes in the screening population, which identified 88, 151, 293, and 53 differentially expressed proteins (DEPs) in exposure/control, silicosis/control, silicosis/exposure, and silicosis stage Ⅲ/silicosis stage Ⅰ groups respectively. After parallel reaction monitoring (PRM) in an independent verification population, the results indicated that the changing trend of 15 DEPs was coincident in screening and verification results. The result of correlation analysis indicated that the plasma level of TNF-α was negatively correlated with the expression of exosomal DSP, KRT78, SERPINB12, and CALML5. The AUC of combined determination of TNF-α and CALML5 reached 0.900, with a sensitivity of 0.714 and a specificity of 0.933. Overall, our study revealed the exosomal proteomic profiling of silicosis patients, silica-exposed workers, and controls, indicating that exosomes were significant in the pathogenesis of silicosis. It also revealed that the combined of the plasma levels of cytokines and the expression of exosomal DEPs could increase determination efficiency. This study provided directions for the development of silicosis biomarkers and a scientific basis for the pathogenesis research of silicosis in the future.

Synthesis of gem-Difluorinated Oxa/Azaspiro[2.4]heptanes via Palladium-Catalyzed Spirocyclopropanation.

A palladium-catalyzed spirocyclopropanation of gem-difluoroalkenes with π-allylpalladium 1,4-dipoles has been successfully developed, which gives a powerful and straightforward synthetic strategy for the construction of novel gem-difluorinated spirocyclic compounds, 6,6-difluoro-5-oxa/azaspiro[2.4]heptanes. The scope of gem-difluoroalkenes can be extended to styrenes, acrylic esters, and acrylamides to realize the installment of various functional groups and different heteroatoms on the spirocyclic skeletons, which could be converted to valuable compounds with potential biological activity. The mechanistic investigations revealed the competition between spirocyclopropanation and ß-F elimination of π-allylpalladium zwitterionic intermediates.

Effects of the SEMA4B gene on hexavalent chromium [Cr(VI)]-induced malignant transformation of human bronchial epithelial cells.

Our previous study identified the potential of SEMA4B methylation level as a biomarker for hexavalent chromium [Cr(VI)] exposure. This study aimed to investigate the role of the SEMA4B gene in Cr(VI)-mediated malignant transformation of human bronchial epithelial (BEAS-2B) cells. In our population survey of workers, the geometric mean [95% confidence intervals (CIs)] of Cr in blood was 3.80 (0.42, 26.56) µg/L. Following treatment with various doses of Cr(VI), it was found that 0.5 µM had negligible effects on the cell viability of BEAS-2B cells. The expression of SEMA4B was observed to decrease in BEAS-2B cells after 7 days of treatment with 0.5 µM Cr(VI), and this downregulation continued with increasing passages of Cr(VI) treatment. Chronic exposure to 0.5 µM Cr(VI) enhanced the anchorage-independent growth ability of BEAS-2B cells. Furthermore, the use of a methylation inhibitor suppressed the Cr(VI)-mediated anchorage-independent growth in BEAS-2B cells. Considering that Cr levels exceeding 0.5 µM can be found in human blood due to occupational exposure, the results suggested a potential carcinogenic risk associated with occupational Cr(VI) exposure through the promotion of malignant transformation. The in vitro study further demonstrated that Cr(VI) exposure might inhibit the expression of the SEMA4B gene to promote the malignant transformation of BEAS-2B cells.

Palladium-catalyzed ring-opening [5+2] annulation of vinylethylene carbonates (VECs) and C5-substituted Meldrum's acids: rapid synthesis of 7-membered lactones.

A novel approach for the synthesis of unsaturated 7-membered lactones by Pd-catalyzed [5+2] dipolar cycloaddition of vinylethylene carbonates (VECs) and C5-substituted Meldrum's acid derivatives has been developed. Various Meldrum's acid derivatives worked well in this reaction under mild reaction conditions. A variety of 7-membered lactones can be accessed in a facile manner in moderate to good yields by employing easily prepared Meldrum's acid derivatives.

An ACC-VTA-ACC positive-feedback loop mediates the persistence of neuropathic pain and emotional consequences.

The central mechanisms underlying pain chronicity remain elusive. Here, we identify a reciprocal neuronal circuit in mice between the anterior cingulate cortex (ACC) and the ventral tegmental area (VTA) that mediates mutual exacerbation between hyperalgesia and allodynia and their emotional consequences and, thereby, the chronicity of neuropathic pain. ACC glutamatergic neurons (ACCGlu) projecting to the VTA indirectly inhibit dopaminergic neurons (VTADA) by activating local GABAergic interneurons (VTAGABA), and this effect is reinforced after nerve injury. VTADA neurons in turn project to the ACC and synapse to the initial ACCGlu neurons to convey feedback information from emotional changes. Thus, an ACCGlu-VTAGABA-VTADA-ACCGlu positive-feedback loop mediates the progression to and maintenance of persistent pain and comorbid anxiodepressive-like behavior. Disruption of this feedback loop relieves hyperalgesia and anxiodepressive-like behavior in a mouse model of neuropathic pain, both acutely and in the long term.

Molybdenum-catalyzed deoxygenative heterocyclization of 2-nitroazobenzenes: a novel strategy for catalytic synthesis of 2-aryl-2H-benzo[d][1,2,3]triazoles.

A novel strategy for the catalytic synthesis of 2-aryl-2H-benzo[d][1,2,3]triazoles bearing a wide range of functional groups in good to excellent yields by non-noble molybdenum-catalyzed deoxygenative heterocyclization of 2-nitroazobenzenes is described. The salient features of the transformation include the use of readily available substrates, valuable products and ease of scale-up. The mechanistic study indicates that the reaction occurred via double deoxygenation by the Mo(VI)/Mo(IV) catalytic cycle from 2-nitroazobenzene, through the formation of 2-aryl-2H-benzo[d][1,2,3]triazole-N1-oxide or nitrene intermediates.

Independent and Combined Associations of Blood Manganese, Cadmium and Lead Exposures with the Systemic Immune-Inflammation Index in Adults.

Manganese (Mn), cadmium (Cd) and lead (Pb) have toxic effects on the immune system. However, their independent and combined effects on immune-inflammation responses are unclear. In recent years, the systemic immune-inflammation index (SII) has been developed as an integrated and novel inflammatory indicator. A retrospective cross-sectional study of 2174 adults ≥20 years old from the National Health and Nutrition Examination Survey (NHANES) 2015-2016 was conducted. Generalized linear models were used to evaluate the independent and combined associations of SII with blood Mn, Cd and Pb levels. As continuous variables, both blood Cd and Mn showed dose-dependent relationships with the SII before and after adjusting for all potential confounding factors. Metal concentrations were then converted into categorical variables. Compared with the adults in the lowest Cd or Mn tertile, those in the highest tertile had higher risks of elevated SII. Furthermore, co-exposure to Mn and Cd also showed a positive relationship with the SII after adjusting for all confounding factors. However, the single effect of Pb exposure and the joint effect of Pb and other metal exposures on the SII were not observed. This study provides important epidemiological evidence of the associations of SII with single and co-exposure effects of blood Mn, Cd, and Pb.

Hexavalent chromium [Cr(VI)]-induced ribosomal DNA copy number variation and DNA damage responses and their associations with nucleolar protein HRAS in humans and cells.

The carcinogenicity of hexavalent chromium [Cr(VI)] and its compounds has been widely recognized, yet the mechanism of genetic damage is still not fully understood. The ribosomal DNA (rDNA) copy number is recently considered a potential marker of cancer-associated stress. To investigate the roles of rDNA copy number variation (CNV) in DNA damage responses (DDRs) induced by Cr(VI) and the potential mechanism from nucleolar protein HRAS, a cross-sectional study in Cr(Ⅵ)-exposed workers and an in vitro experiment using HeLa cells were conducted. Our results showed increased levels of rDNA CNV, DDRs, and HRAS expression in Cr(VI)-exposed workers. Generalized linear regression analyses showed that Cr(VI) exposure was significantly positively associated with increased levels of rDNA CNV, DDRs, and HRAS expression in Cr(VI)-exposed workers. Moreover, there were pairwise associations between rDNA CNV, DDRs, and HRAS levels. Mediation analyses found that rDNA CNV significantly mediated the association between Cr(VI) exposure and DDRs. The in vitro experiments further confirmed that Cr(VI) treatment induced increased levels of rDNA CNV, DDRs, and HRAS expression in HeLa cells. Cr(VI)-induced rDNA CNV, ATM activation, and apoptosis damage were then strongly enhanced by HRAS depletion with siRNA in vitro, suggesting the important role of HRAS in CNV and DDRs caused by Cr(VI). The combined results of the human and cell line studies indicated that Cr(VI) exposure might enhance rDNA CNV by regulation of HRAS expression, which leads to Cr(VI)-induced genetic damage.

The Hypervelocity Impact Behavior and Energy Absorption Evaluation of Fabric.

In this work, the mechanical behavior and energy absorption characteristics of flexible fabric under hypervelocity impact (HVI) were investigated. Basalt fabric, ultra-high molecular weight polyethylene (UHMWPE) fabric, and aluminum alloy (Al) plate were chosen to be the sample materials for their excellent mechanical properties and applicative prospect in spacecraft shielding. HVI experiments had been conducted with the help of a two-stage light-gas gun facility, wherein Al projectile with 3.97 mm diameter was launched at velocities in the range 4.1~4.3 km/s. Impact conditions and areal density were kept constant for all targets. The microstructural damage morphology of fiber post-impact was characterized using a scanning electron microscope (SEM). Analysis results show that a brittle fracture occurred for Basalt fiber during HVI. On the contrary, the ductile fractures with large-scale plastic deformation and apparent thermal softening/melting of the material had happened on the UHMWPE fiber when subjected to a projectile impact. According to the HVI shielding performance and microstructural damage analysis results, it can be inferred that ductile fractures and thermal softening/melting of the material were the prevailing energy absorption behaviors of UHMWPE fabric, which leads to absorbing more impact energy than Basalt fabric and eventually, contributes the superior shielding performance.

Association of Dietary α-Carotene and ß-Carotene Intake with Low Cognitive Performance in Older Adults: A Cross-Sectional Study from the National Health and Nutrition Examination Survey.

This study aims to examine the relationships of dietary α-carotene and ß-carotene intake with cognitive function. The data were selected from the National Health and Nutrition Examination Survey (NHANES) 2011-2014. A total of 2009 participants were included in this analysis. Dietary α-carotene and ß-carotene intake were averaged by two 24-h dietary recalls. The Consortium to Establish a Registry for Alzheimer's Disease Word Learning subset (CERAD W-L), Animal Fluency Test (AFT), and Digit Symbol Substitution Test (DSST) were used to evaluate cognitive function. Logistic regression and restricted cubic spline models were applied to explore the associations of dietary α-carotene and ß-carotene intake with cognitive performance. After adjusting for all confounding factors, compared with individuals in the lowest quartile of ß-carotene dietary intake, those in the highest quartile had lower risks of both CERAD W-L decline [odds ratio (OR) = 0.63, 95% confidence interval (CI): 0.44-0.90] and AFT decline (OR = 0.66, 95% CI: 0.47-0.94). In addition, the third quartile of ß-carotene dietary intake had a significantly decreased risk of lower DSST (OR = 0.67, 95% CI: 0.48-0.83). Compared with the lowest quartile of α-carotene intake, the OR of AFT decline in the highest intake quartile was 0.66 (95% CI: 0.46, 0.94). For males, both dietary α-carotene and ß-carotene intake were associated with a decreased risk of AFT decline (OR = 0.42, 95% CI: 0.25-0.71; OR = 0.51, 95% CI: 0.30-0.85, respectively). For females, dietary α-carotene intake was associated with a decreased risk of CERAD W-L decline (OR = 0.55, 95% CI: 0.33-0.91) and dietary ß-carotene intake was associated with decreased risks of both CERAD W-L and AFT decline (OR = 0.37, 95% CI: 0.21-0.64; OR = 0.58, 95% CI: 0.37-0.91, respectively). Our results suggested that higher dietary α-carotene and ß-carotene intake had inverse effects on cognitive function decline among older adults.

Systemic immune-inflammation index is associated with decreased bone mass density and osteoporosis in postmenopausal women but not in premenopausal women.

Purpose: This study aims to investigate the associations of the systemic immune-inflammation index (SII) with bone mineral density (BMD) and osteoporosis in adult females from a nationally representative sample. Methods: A cross-sectional study was performed among 4092 females aged ≥20 years from the National Health and Nutrition Examination Survey 2007-2010. Linear and logistic regressions were applied to explore the relationships of SII with BMD and the risk of osteoporosis, respectively. Results: Linear regression analyses found that a doubling of SII levels was significantly correlated with a 1.39% (95% CI: 0.57%, 2.20%) decrease in total femur BMD, a 1.16% (95% CI: 0.31%, 2.00%) decrease in femur neck BMD, a 1.73% (95% CI: 0.78%, 2.66%) decrease in trochanter BMD, and a 1.35% (95% CI: 0.50%, 2.20%) decrease in intertrochanteric BMD among postmenopausal women, after adjusting for covariates. Logistic regression analyses showed that compared with postmenopausal women in the lowest SII quartile, those in the highest quartile had higher risks of osteoporosis in the total femur (odds ratio (OR) = 1.70, 95% CI: 1.04, 2.76), trochanter (OR = 1.86, 95% CI: 1.07, 3.38), intertrochanter (OR = 2.01, 95% CI: 1.05, 4.04) as well as overall osteoporosis (OR = 1.57, 95% CI: 1.04, 2.37). In contrast, there was no significant association between SII and BMD in premenopausal women. Conclusions: SII levels were negatively associated with BMD levels in postmenopausal women but not in premenopausal women. Elevated SII levels could be a potential risk factor for osteoporosis in postmenopausal women.

A soybean sodium/hydrogen exchanger GmNHX6 confers plant alkaline salt tolerance by regulating Na+/K+ homeostasis.

Alkaline soil has a high pH due to carbonate salts and usually causes more detrimental effects on crop growth than saline soil. Sodium hydrogen exchangers (NHXs) are pivotal regulators of cellular Na+/K+ and pH homeostasis, which is essential for salt tolerance; however, their role in alkaline salt tolerance is largely unknown. Therefore, in this study, we investigated the function of a soybean NHX gene, GmNHX6, in plant response to alkaline salt stress. GmNHX6 encodes a Golgi-localized sodium/hydrogen exchanger, and its transcript abundance is more upregulated in alkaline salt tolerant soybean variety in response to NaHCO3 stress. Ectopic expression of GmNHX6 in Arabidopsis enhanced alkaline salt tolerance by maintaining high K+ content and low Na+/K+ ratio. Overexpression of GmNHX6 also improved soybean tolerance to alkaline salt stress. A single nucleotide polymorphism in the promoter region of NHX6 is associated with the alkaline salt tolerance in soybean germplasm. A superior promoter of GmNHX6 was isolated from an alkaline salt tolerant soybean variety, which showed stronger activity than the promoter from an alkaline salt sensitive soybean variety in response to alkali stress, by luciferase transient expression assays. Our results suggested soybean NHX6 gene plays an important role in plant tolerance to alkaline salt stress.

Intakes of Folate, Vitamin B6, and Vitamin B12 in Relation to All-Cause and Cause-Specific Mortality: A National Population-Based Cohort.

The evidence regarding the intake of dietary folate, vitamin B6, and vitamin B12 in relation to mortality in the general population is limited. This study aimed to examine the relationship between dietary intakes of folate, vitamin B6, and vitamin B12 in relation to all-cause and cause-specific mortality in a large U.S. cohort. This study included a total of 55,569 adults from the Third National Health and Nutrition Examination Survey (NHANES III) and NHANES 1999-2014. Vital data were determined by linking with the National Death Index records through 31 December 2015. Cox proportional hazards models were used to investigate the relationships of all-cause and cause-specific mortality with dietary folate, vitamin B6, and vitamin B12 intake. Dietary intakes of folate and vitamin B6 were inversely associated with mortality from all-cause, cardiovascular disease, and cancer for men and with mortality from all-cause and cardiovascular disease for women. In men, the multivariable hazard ratios (95% confidence intervals) for the highest versus lowest quintiles of folate and vitamin B6 were 0.77 (0.71-0.85) and 0.79 (0.71-0.86) for all-cause mortality, 0.59 (0.48-0.72) and 0.69 (0.56-0.85) for CVD mortality, and 0.68 (0.56-0.84) and 0.73 (0.60-0.90) for cancer mortality, respectively. Among women, the multivariable hazard ratios (95% confidence intervals) for the highest versus lowest quintiles of folate and vitamin B6 were 0.86 (0.78-0.95) and 0.88 (0.80-0.97) for all-cause mortality and 0.53 (0.41-0.69) and 0.56 (0.44-0.73) for CVD mortality, respectively. No significant associations between dietary vitamin B12 and all-cause and cause-specific mortality were observed. In conclusion, higher dietary intakes of folate and vitamin B6 were significantly associated with lower all-cause and cardiovascular mortality. Our findings suggest that increasing the intake of folate and vitamin B6 may lower the mortality risk among U.S. adults.

Synaptotagmin-1 is a bidirectional Ca2+ sensor for neuronal endocytosis.

Exocytosis and endocytosis are tightly coupled. In addition to initiating exocytosis, Ca2+ plays critical roles in exocytosis­endocytosis coupling in neurons and nonneuronal cells. Both positive and negative roles of Ca2+ in endocytosis have been reported; however, Ca2+ inhibition in endocytosis remains debatable with unknown mechanisms. Here, we show that synaptotagmin-1 (Syt1), the primary Ca2+ sensor initiating exocytosis, plays bidirectional and opposite roles in exocytosis­endocytosis coupling by promoting slow, small-sized clathrin-mediated endocytosis but inhibiting fast, large-sized bulk endocytosis. Ca2+-binding ability is required for Syt1 to regulate both types of endocytic pathways, the disruption of which leads to inefficient vesicle recycling under mild stimulation and excessive membrane retrieval following intense stimulation. Ca2+-dependent membrane tubulation may explain the opposite endocytic roles of Syt1 and provides a general membrane-remodeling working model for endocytosis determination. Thus, Syt1 is a primary bidirectional Ca2+ sensor facilitating clathrin-mediated endocytosis but clamping bulk endocytosis, probably by manipulating membrane curvature to ensure both efficient and precise coupling of endocytosis to exocytosis.