DRG2 is required for surface localization of PD-L1 and the efficacy of anti-PD-1 therapy.

More than half of tumor patients with high PD-L1 expression do not respond to anti-PD-1/PD-L1 therapy, and the underlying mechanisms are yet to be clarified. Here we show that developmentally regulated GTP-binding protein 2 (DRG2) is required for response of PD-L1-expressing tumors to anti-PD-1 therapy. DRG2 depletion enhanced IFN-γ signaling and increased the PD-L1 level in melanoma cells. However, it inhibited recycling of endosomal PD-L1 and reduced surface PD-L1 levels, which led to defects in interaction with PD-1. Anti-PD-1 did not expand effector-like T cells within DRG2-depleted tumors and failed to improve the survival of DRG2-depleted tumor-bearing mice. Cohort analysis revealed that patients bearing melanoma with low DRG2 protein levels were resistant to anti-PD-1 therapy. These findings identify DRG2 as a key regulator of recycling of endosomal PD-L1 and response to anti-PD-1 therapy and provide insights into how to increase the correlation between PD-L1 expression and response to anti-PD-1 therapy.

Plasma Metanephrines Yield Fewer False-Positive Results Than Urine Metanephrines in Patients With Obstructive Sleep Apnea.

CONTEXT: Obstructive sleep apnea (OSA) is associated with increased nocturnal sympathetic activity. In OSA patients, elevations in metanephrines may lead to false-positive tests when evaluating for pheochromocytoma or paraganglioma (PPGL). OBJECTIVE: To evaluate whether morning plasma metanephrines would lead to fewer false-positive results than 24-hour urinary metanephrines in OSA patients. METHODS: Patients undergoing polysomnography for suspected OSA were recruited. Plasma free and 24-hour urinary metanephrines were measured by HPLC-MS/MS. Patients with elevated levels had repeat measurements, abdominal imaging, and follow-up to diagnose or exclude a PPGL. RESULTS: Seventy-six patients completed polysomnography and biochemical testing; 68 (89.5%) patients had OSA, of whom 19 (27.9%) had elevated plasma and/or urinary metanephrines. On follow-up, one patient had a bladder paraganglioma, while PPGL was excluded in the remaining patients. OSA patients had more false-positive urinary metanephrines (17 of 67, 25.4%) than plasma metanephrines (2 of 67, 3.0%), P < .01, and this was more common in severe OSA (13 of 34, 38.2%), compared to moderate/mild OSA (4 of 33, 12.1%), P < .01. Both plasma and urinary metanephrines decreased after treatment with continuous positive airway pressure. On multivariable analysis, severe OSA, obesity, and family history of hypertension were positive predictors for false-positive urinary metanephrines in patients with suspected OSA. CONCLUSION: In OSA patients, plasma metanephrines are less likely to yield false-positive results for the diagnosis of PPGL than 24-hour urinary metanephrines. In patients with suspected OSA, obesity, or a family history of hypertension, plasma metanephrines may be the preferred first-line test to avoid unnecessary anxiety or follow-up.

CADPS functional mutations in patients with bipolar disorder increase the sensitivity to stress.

Bipolar disorder is a severe and chronic psychiatric disease resulting from a combination of genetic and environmental risk factors. Here, we identified a significant higher mutation rate in a gene encoding the calcium-dependent activator protein for secretion (CADPS) in 132 individuals with bipolar disorder, when compared to 184 unaffected controls or to 21,070 non-psychiatric and non-Finnish European subjects from the Exome Aggregation Consortium. We found that most of these variants resulted either in a lower abundance or a partial impairment in one of the basic functions of CADPS in regulating neuronal exocytosis, synaptic plasticity and vesicular transporter-dependent uptake of catecholamines. Heterozygous mutant mice for Cadps+/- revealed that a decreased level of CADPS leads to manic-like behaviours, changes in BDNF level and a hypersensitivity to stress. This was consistent with more childhood trauma reported in families with mutation in CADPS, and more specifically in mutated individuals. Furthermore, hyperactivity observed in mutant animals was rescued by the mood-stabilizing drug lithium. Overall, our results suggest that dysfunction in calcium-dependent vesicular exocytosis may increase the sensitivity to environmental stressors enhancing the risk of developing bipolar disorder.

Improvement in quality of life and psychological symptoms after treatment for primary aldosteronism: Asian Cohort Study.

BACKGROUND: In addition to increased cardiovascular risk, patients with primary aldosteronism (PA) also suffer from impaired health-related quality of life (HRQoL) and psychological symptoms. We assessed for changes in HRQoL and depressive symptoms in a cohort of Asian patients with PA, after surgical and medical therapy. METHODS: Thirty-four patients with PA were prospectively recruited and completed questionnaires from 2017 to 2020. HRQoL was assessed using RAND-36 and EQ-5D-3L, and depressive symptoms were assessed using Beck Depression Inventory (BDI-II) at baseline, 6 months, and 1 year post-treatment. RESULTS: At 1 year post-treatment, significant improvement was observed in both physical and mental summative scores of RAND-36, +3.65, P = 0.023, and +3.41, P = 0.033, respectively, as well as four subscale domains (physical functioning, bodily pain, role emotional, and mental health). Significant improvement was also seen in EQ-5D dimension of anxiety/depression at 1 year post-treatment. Patients treated with surgery (n = 21) had significant improvement in EQ-5D index score post-treatment and better EQ-5D outcomes compared to the medical group (n = 13) at 1 year post-treatment. 37.9, 41.6 and 58.6% of patients had symptoms in the cognitive, affective and somatic domains of BDI-II, respectively. There was a significant improvement in the affective domain of BDI-II at 1 year post-treatment. CONCLUSION: Both surgical and medical therapy improve HRQoL and psychological symptoms in patients with PA, with surgery providing better outcomes. This highlights the importance of early diagnosis, accurate subtyping and appropriate treatment of PA.

Bone mineral density and trabecular bone score in elderly type 2 diabetes Southeast Asian patients with severe osteoporotic hip fractures.

INTRODUCTION: Studies show trabecular bone score (TBS) may provide information regarding bone quality independent of bone mineral density (BMD) in type 2 diabetes (DM2) patients. We analyzed our Southeast Asian severe osteoporotic hip fracture patients to study these differences. METHODS: We conducted a retrospective cross-sectional analysis of subjects admitted to Changi General Hospital, Singapore with severe osteoporotic hip fractures from 2014-2017 who had BMD performed. Electronic records were reviewed and subjects were classified as having diabetes according to the WHO 2019 criteria. DM2 patients were classified according to their HbA1c into well controlled (HbA1c < 7%) and poorly controlled (HbA1c ≥ 7%) DM2. RESULTS: Elderly patients with hip fractures present with average femur neck T scores at the osteoporotic range, however those with DM2 had higher BMD and TBS values compared to non DM2 patients. These differences were statistically significant in elderly women-poorly controlled elderly DM2 women with hip fracture had the highest total hip T-score (-2.57 ± 0.86) vs (-2.76 ± 0.96) in well controlled DM2 and (-3.09 ± 1.01) in non DM2 women with hip fracture, p < 0.001. In contrast, TBS scores were lower in poorly controlled DM2 women with hip fracture compared to well controlled DM2 women with hip fracture (1.22 ± 0.11) vs (1.24 ± 0.09), but these were still significantly higher compared to non DM2 women with hip fracture (1.19 ± 0.10), p < 0.001. In elderly men with hip fractures, univariate analysis showed no statistically significant differences in TBS or hip or LS BMD between those with poorly controlled DM2, well controlled DM2 and non DM2. The differences in TBS and BMD remained significant in all DM2 women with hip fractures even after adjustments for potential confounders. Differences in TBS and BMD in poorly controlled DM2 men with hip fractures only became significant after accounting for potential confounders. However, upon inclusion of LS BMD into the multivariate model these differences were attenuated and remained significant only between elderly women with well controlled DM2 and non DM2 women with hip fractures. CONCLUSIONS: Elderly patients with DM2 and severe osteoporosis present with hip fractures at a higher BMD and TBS values compared to non DM2 patients. These differences were significant after adjustment for confounders in all DM2 women and poorly controlled DM2 men with hip fractures, TBS differences were attenuated with the inclusion LS BMD. Further studies are needed to ascertain differences in BMD and TBS in older Southeast Asian DM2 patients with variable glycemic control and severe osteoporosis.

The priming factor CAPS1 regulates dense-core vesicle acidification by interacting with rabconnectin3ß/WDR7 in neuroendocrine cells.

Vacuolar-type H+-ATPases (V-ATPases) contribute to pH regulation and play key roles in secretory and endocytic pathways. Dense-core vesicles (DCVs) in neuroendocrine cells are maintained at an acidic pH, which is part of the electrochemical driving force for neurotransmitter loading and is required for hormonal propeptide processing. Genetic loss of CAPS1 (aka calcium-dependent activator protein for secretion, CADPS), a vesicle-bound priming factor required for DCV exocytosis, dissipates the pH gradient across DCV membranes and reduces neurotransmitter loading. However, the basis for CAPS1 binding to DCVs and for its regulation of vesicle pH has not been determined. Here, MS analysis of CAPS1 immunoprecipitates from brain membrane fractions revealed that CAPS1 associates with a rabconnectin3 (Rbcn3) complex comprising Dmx-like 2 (DMXL2) and WD repeat domain 7 (WDR7) proteins. Using immunofluorescence microscopy, we found that Rbcn3α/DMXL2 and Rbcn3ß/WDR7 colocalize with CAPS1 on DCVs in human neuroendocrine (BON) cells. The shRNA-mediated knockdown of Rbcn3ß/WDR7 redistributed CAPS1 from DCVs to the cytosol, indicating that Rbcn3ß/WDR7 is essential for optimal DCV localization of CAPS1. Moreover, cell-free experiments revealed direct binding of CAPS1 to Rbcn3ß/WDR7, and cell assays indicated that Rbcn3ß/WDR7 recruits soluble CAPS1 to membranes. As anticipated by the reported association of Rbcn3 with V-ATPase, we found that knocking down CAPS1, Rbcn3α, or Rbcn3ß in neuroendocrine cells impaired rates of DCV reacidification. These findings reveal a basis for CAPS1 binding to DCVs and for CAPS1 regulation of V-ATPase activity via Rbcn3ß/WDR7 interactions.

Effects of Estrogen Therapies on Outcomes in Turner Syndrome: Assessment of Induction of Puberty and Adult Estrogen Use.

CONTEXT: Turner syndrome (TS) is often associated with delayed puberty. To induce puberty, estrogen is administered in incremental doses at an age determined by age of presentation. After puberty, various types of maintenance estrogen replacement therapy (ERT) are used. OBJECTIVE: We sought associations between age of induction of puberty and type of ERT on adult health outcomes. DESIGN: Health surveillance data included blood profiles, bone density, and blood pressure. We assessed interactions between these data and age at first estrogen exposure in women with primary amenorrhea. We also assessed these data according to ERT subgroups [combined oral contraceptive pill (OCP), oral estrogen (OE), and transdermal estradiol (TE)] using data from each of 6679 clinic visits, controlling for age, body mass index, and height. SETTING: Adult TS clinic at University College London Hospital. PATIENTS: Of 799 women with TS, 624 had primary amenorrhea and 599 had accurate maintenance ERT data. MAIN OUTCOME MEASURES: Parameters of health surveillance derived from clinical guidelines. RESULTS: Estrogen start age was negatively correlated with adult bone density (spine: r = -0.20 and hip: r = -0.022; P ≤ 0.001). OCP users had higher blood pressure and an adverse lipid profile compared with other ERT subgroups. TE was associated with elevated liver enzymes and hemoglobin A1c compared with OE (P ≤ 0.01). CONCLUSIONS: An earlier age of induction of puberty may be beneficial for adult bone density. Given the high prevalence of hypertension in TS, the use of OCP for ERT should be limited. OE may be a benefit for steatohepatitis.

Managing polycystic ovary syndrome in primary care.

Polycystic ovary syndrome (PCOS) presents with a spectrum of conditions resulting from androgen excess, anovulation and metabolic syndrome. Patients with PCOS may see their primary care physicians for various presentations, including hirsutism, acne, menstrual irregularities, infertility, obesity, and psychiatric disorders such as anxiety and depression. Management of these patients should include screening for Type 2 diabetes mellitus, dyslipidaemia and hypertension. Treatment should be targeted to each patient's phenotype and personal expectations such as desire for pregnancy. Psychological well-being due to the effects on physical appearance is also an important consideration. Diet and exercise are major components in the management of patients with PCOS and obesity. The first-line therapy for fertility and metabolic syndrome in PCOS is lifestyle modification with diet and exercise, followed by pharmacological therapy.

A Ca2+-stimulated exosome release pathway in cancer cells is regulated by Munc13-4.

Cancer cells secrete copious amounts of exosomes, and elevated intracellular Ca2+ is critical for tumor progression and metastasis, but the underlying cellular mechanisms are unknown. Munc13-4 is a Ca2+-dependent SNAP receptor- and Rab-binding protein required for Ca2+-dependent membrane fusion. Here we show that acute elevation of Ca2+ in cancer cells stimulated a fivefold increase in CD63+, CD9+, and ALIX+ exosome release that was eliminated by Munc13-4 knockdown and not restored by Ca2+ binding-deficient Munc13-4 mutants. Direct imaging of CD63-pHluorin exosome release confirmed its Munc13-4 dependence. Depletion of Munc13-4 in highly aggressive breast carcinoma MDA-MB-231 cells reduced the size of CD63+ multivesicular bodies (MVBs), indicating a role for Munc13-4 in MVB maturation. Munc13-4 used a Rab11-dependent trafficking pathway to generate MVBs competent for exosome release. Membrane type 1 matrix metalloproteinase trafficking to MVBs by a Rab11-dependent pathway was also Munc13-4 dependent, and Munc13-4 depletion reduced extracellular matrix degradation. These studies identify a novel Ca2+- and Munc13-4-dependent pathway that underlies increased exosome release by cancer cells.

Small molecules that inhibit the late stage of Munc13-4-dependent secretory granule exocytosis in mast cells.

Ca2+-dependent secretory granule fusion with the plasma membrane is the final step for the exocytic release of inflammatory mediators, neuropeptides, and peptide hormones. Secretory cells use a similar protein machinery at late steps in the regulated secretory pathway, employing protein isoforms from the Rab, Sec1/Munc18, Munc13/CAPS, SNARE, and synaptotagmin protein families. However, no small-molecule inhibitors of secretory granule exocytosis that target these proteins are currently available but could have clinical utility. Here we utilized a high-throughput screen of a 25,000-compound library that identified 129 small-molecule inhibitors of Ca2+-triggered secretory granule exocytosis in RBL-2H3 mast cells. These inhibitors broadly fell into six different chemical classes, and follow-up permeable cell and liposome fusion assays identified the target for one class of these inhibitors. A family of 2-aminobenzothiazoles (termed benzothiazole exocytosis inhibitors or bexins) was found to inhibit mast cell secretory granule fusion by acting on a Ca2+-dependent, C2 domain-containing priming factor, Munc13-4. Our findings further indicated that bexins interfere with Munc13-4-membrane interactions and thereby inhibit Munc13-4-dependent membrane fusion. We conclude that bexins represent a class of specific secretory pathway inhibitors with potential as therapeutic agents.

High Throughput NPY-Venus and Serotonin Secretion Assays for Regulated Exocytosis in Neuroendocrine Cells.

Here we describe two assays to measure dense core vesicle (DCV) exocytosis-mediated cargo secretion in neuroendocrine cells. To conduct siRNA screens for novel genes in regulated DCV exocytosis, we developed a plate reader-based secretion assay using DCV cargo, NPY-Venus, and an orthogonal 3H-serotonin secretion assay. The NPY-Venus secretion assay was successfully used for a high throughput siRNA screen, and the serotonin secretion assay was used to validate hits identified from the screen (Sorensen, 2017; Zhang et al., 2017).

Managing polycystic ovary syndrome in primary care

Polycystic ovary syndrome (PCOS) presents with a spectrum of conditions resulting from androgen excess, anovulation and metabolic syndrome. Patients with PCOS may see their primary care physicians for various presentations, including hirsutism, acne, menstrual irregularities, infertility, obesity, and psychiatric disorders such as anxiety and depression. Management of these patients should include screening for Type 2 diabetes mellitus, dyslipidaemia and hypertension. Treatment should be targeted to each patient's phenotype and personal expectations such as desire for pregnancy. Psychological well-being due to the effects on physical appearance is also an important consideration. Diet and exercise are major components in the management of patients with PCOS and obesity. The first-line therapy for fertility and metabolic syndrome in PCOS is lifestyle modification with diet and exercise, followed by pharmacological therapy.

BAIAP3, a C2 domain-containing Munc13 protein, controls the fate of dense-core vesicles in neuroendocrine cells.

Dense-core vesicle (DCV) exocytosis is a SNARE (soluble N-ethylmaleimide-sensitive fusion attachment protein receptor)-dependent anterograde trafficking pathway that requires multiple proteins for regulation. Several C2 domain-containing proteins are known to regulate Ca2+-dependent DCV exocytosis in neuroendocrine cells. In this study, we identified others by screening all (∼139) human C2 domain-containing proteins by RNA interference in neuroendocrine cells. 40 genes were identified, including several encoding proteins with known roles (CAPS [calcium-dependent activator protein for secretion 1], Munc13-2, RIM1, and SYT10) and many with unknown roles. One of the latter, BAIAP3, is a secretory cell-specific Munc13-4 paralog of unknown function. BAIAP3 knockdown caused accumulation of fusion-incompetent DCVs in BON neuroendocrine cells and lysosomal degradation (crinophagy) of insulin-containing DCVs in INS-1 ß cells. BAIAP3 localized to endosomes was required for Golgi trans-Golgi network 46 (TGN46) recycling, exhibited Ca2+-stimulated interactions with TGN SNAREs, and underwent Ca2+-stimulated TGN recruitment. Thus, unlike other Munc13 proteins, BAIAP3 functions indirectly in DCV exocytosis by affecting DCV maturation through its role in DCV protein recycling. Ca2+ rises that stimulate DCV exocytosis may stimulate BAIAP3-dependent retrograde trafficking to maintain DCV protein homeostasis and DCV function.

Hormone replacement treatment choices in complete androgen insensitivity syndrome: an audit of an adult clinic.

OBJECTIVE: To review the treatment choices of women with complete androgen insensitivity syndrome (CAIS) at a single tertiary centre. DESIGN: Retrospective review. PATIENTS: Women with CAIS identified from our database. RESULTS: The study group comprised 141 women with CAIS. Eleven percent (16/141) of women had gonads in situ, 3 of whom were under workup for gonadectomy. The age of gonadectomy in the remainder 125 women was 17 (0.1-53) years. The most common form of HRT was oral oestrogen or transdermal oestrogen in 80% (113/141). 13/141 (9%) women used vaginal oestrogens alone or together with other forms of HRT. Testosterone preparations had been used by 17% (24/141) of women and were currently used in 10% (14/141). Of those who had used testosterone, 42% (10/24) had chosen not to continue after a therapeutic trial. CONCLUSIONS: In a clinic offering individualised multidisciplinary care for women with CAIS, we found that the majority of women chose oestrogen-based treatment while a significant minority used testosterone.

High prevalence of missed opportunities for secondary fracture prevention in a regional general hospital setting in Singapore.

This study aims at assessing the gap in secondary fracture prevention at a regional general hospital setting in Singapore. Male patients have significantly lower rate of being investigated and treated for osteoporosis than their female counterparts. Vitamin D deficiency is prevalent in our population. PURPOSE: Secondary fracture prevention services are not routine in Singapore; we seek to assess the treatment gap that exists in the lack of diagnosis and treatment of osteoporosis in fragility fracture patients. METHODS: We performed a retrospective analysis of all admissions for fragility fractures between December 2013 and December 2014. Demographic data, rates of BMD performance, serum vitamin D investigation and calcium and vitamin D supplementation as well as antiresorptive initiation 1 year post admission were analysed. RESULTS: There were 125 fragility fractures in patients below 65 and 615 fractures in older patients. There was a slightly higher proportion of males in the younger population, whereas females predominated in the older population. Median vitamin D levels were low in both younger (19.1 µg/L) and older (22.0 µg/L) groups, but supplementation was lower in younger patients (4.8 versus 16.6%, p = 0.003). Rate of BMD performance was lower in younger patients (34.4 versus 64.6%, p < 0.01); there was a significant difference of BMD performance between male and female patients in the younger population (19.1 versus 52.8%, p < 0.01) which was not present in the older age group. Antiresportive initiation was significantly lower in the younger age group versus older (10.4 versus 31.5%, p < 0.01); male patients in the younger and older age groups had significantly lower antiresorptive initiation rate compared to the females. CONCLUSION: There is a significant treatment gap in diagnosis and treatment of osteoporosis in fragility fracture patients in a regional hospital setting in Singapore. Male osteoporosis remains inadequately investigated and treated in both age groups.

The Turner syndrome life course project: Karyotype-phenotype analyses across the lifespan.

INTRODUCTION: Turner syndrome (TS) is associated with a variety of morbidities affecting nearly every body system, some of which increase in prevalence in adult life. The severity of clinical features in TS is roughly in parallel with the magnitude of the deficit of X-chromosome material. The aim of this study was to extend the established karyotype-phenotype relationships using data from a large adult cohort. MATERIALS AND METHODS: Karyotypes were available in 656 women with TS. 611 of whom could be classified into five major groups within the cohort: 45,X; 45,X mosaicism (45,X/46,XX); isochromosome X (isochromosome Xq); mosaicism 45,X/46,XY and ring X. Continuous variables such as blood pressure and biochemical markers from clinic data were binarised allocating those in the upper quartile to represent at-risk individuals. With the exception of bone mineral density T-score for which the lower quartile was allocated as at risk. For comorbidities, initiation of formal treatment was recorded. RESULTS: 45,X/46,XX had considerably lower frequency of comorbidities compared to 45,X. The isochromosome group experienced similar outcomes to 45,X. Novel associations were found between the XY mosaic karyotype group and a decreased prevalence of thyroid disease and severe hearing loss. A previously unreported increased incidence of metabolic syndrome was noted within the ring chromosome subgroup. CONCLUSIONS: Karyotype may play an important factor against stratifying risk of comorbidity in TS and should be taken into consideration when managing adults with TS. Further investigations of the isochromosome (Xq) and ring groups are necessary to further clarify their associations with comorbidities.

Bone mineral density in complete androgen insensitivity syndrome and the timing of gonadectomy.

OBJECTIVE: Low bone mineral density (BMD) has been reported in complete androgen insensitivity syndrome (CAIS), but the impact of timing of gonadectomy is not known. We aimed to assess the relationship between age of gonadectomy and BMD in women with CAIS. DESIGN: Retrospective analysis of pre- and post-gonadectomy parameters in women with CAIS attending an adult Disorders of Sex Development (DSD) clinic in a tertiary centre. PATIENTS: One hundred and thirteen women with CAIS. MEASUREMENTS: Dual-energy X-ray absorptiometry (DXA) before and after gonadectomy; and pre-gonadectomy hormone profile. RESULTS: Mean BMD was reduced (95% confidence interval); T-score -1.34 (-1.55 to -1.13; P<.001) at the lumbar spine and -0.3 (-0.49 to -0.12; P=.001) at the hip. There was no relationship between age of gonadectomy and BMD. Thirty-two subjects had BMD measured before or within 2 years of gonadectomy, and mean BMD was reduced (95% CI) at the lumbar spine; T-score: -1.05 (-1.54 to -0.57; P<.001), but was normal at the hip; T-score -0.04 (-0.35 to 0.28; P=.8). There was no relationship between BMD and history of hernia, testosterone, oestradiol or follicle stimulating hormone levels. Twelve subjects had DXA both before and after gonadectomy, and after 4.3 (1.7-12.8) years, there was no change in BMD. CONCLUSIONS: We found reduced BMD at the spine and hip in subjects with CAIS. We found no relationship between age of gonadectomy and BMD, and we also found no drop in BMD in subjects followed up after gonadectomy.

A novel Munc13-4/S100A10/annexin A2 complex promotes Weibel-Palade body exocytosis in endothelial cells.

Endothelial cells respond to blood vessel injury by the acute release of the procoagulant von Willebrand factor, which is stored in unique secretory granules called Weibel-Palade bodies (WPBs). Stimulated WPB exocytosis critically depends on their proper recruitment to the plasma membrane, but factors involved in WPB-plasma membrane tethering are not known. Here we identify Munc13-4, a protein mutated in familial hemophagocytic lymphohistiocytosis 3, as a WPB-tethering factor. Munc13-4 promotes histamine-evoked WPB exocytosis and is present on WPBs, and secretagogue stimulation triggers an increased recruitment of Munc13-4 to WPBs and a clustering of Munc13-4 at sites of WPB-plasma membrane contact. We also identify the S100A10 subunit of the annexin A2 (AnxA2)-S100A10 protein complex as a novel Munc13-4 interactor and show that AnxA2-S100A10 participates in recruiting Munc13-4 to WPB fusion sites. These findings indicate that Munc13-4 supports acute WPB exocytosis by tethering WPBs to the plasma membrane via AnxA2-S100A10.