A partnership between the lipid scramblase XK and the lipid transfer protein VPS13A at the plasma membrane

Chorea-acanthocytosis (ChAc) and McLeod syndrome are diseases with shared clinical manifestations caused by mutations in VPS13A and XK, respectively. Key features of these conditions are the degeneration of caudate neurons and the presence of abnormally shaped erythrocytes. XK belongs to a family of plasma membrane (PM) lipid scramblases whose action results in exposure of PtdSer at the cell surface. VPS13A is an endoplasmic reticulum (ER)-anchored lipid transfer protein with a putative role in the transport of lipids at contacts of the ER with other membranes. Recently VPS13A and XK were reported to interact by still unknown mechanisms. So far, however, there is no evidence for a colocalization of the two proteins at contacts of the ER with the PM, where XK resides, as VPS13A was shown to be localized at contacts between the ER and either mitochondria or lipid droplets. Here we show that VPS13A can also localize at ER–PM contacts via the binding of its PH domain to a cytosolic loop of XK, that such interaction is regulated by an intramolecular interaction within XK, and that both VPS13A and XK are highly expressed in the caudate neurons. Binding of the PH domain of VPS13A to XK is competitive with its binding to intracellular membranes that mediate other tethering functions of VPS13A. Our findings support a model according to which VPS13A-dependent lipid transfer between the ER and the PM is coupled to lipid scrambling within the PM. They raise the possibility that defective cell surface exposure of PtdSer may be responsible for neurodegeneration.

Chorea-acanthocytosis (ChAc) and McLeod syndrome (MLS) are two similar diseases, characterized by progressive degeneration of the caudate nucleus leading to chorea and other movement defects and by abnormally shaped erythrocytes (acanthocytes). Chorea-acanthocytosis is due to loss of function of VPS13A (1, 2), the founding member of a superfamily of lipid transport proteins, also called chorein motif proteins because of the high conservation of their most N-terminal region (∼120 amino acids [aa]), referred to as the chorein motif. Members of this superfamily, which also comprises the autophagy factor ATG2, are localized at membrane contact sites where they are thought to transfer lipids unidirectionally between adjacent bilayers of different organelles by a bridge-like mechanism (3–5). McLeod syndrome is due instead to loss of function of XK (6), a member of a family of lipid scramblases whose function is to collapse the heterogeneity of the lipid composition of the two leaflets of the plasma membrane (PM) (7). A consequence of this scrambling is the exposure to the cell surface of PtdSer, a phospholipid that is recognized by phagocytic cells and normally concentrated in the cytosolic leaflet of the PM by the action of flippases (8).Consistent with the similarity of the clinical conditions resulting from mutations in VPS13A and in XK, there is evidence suggesting that the two proteins are functional partners (9–11). Thus, it is of great interest that both proteins are implicated in lipid transport. More importantly, as chorein motif proteins do not penetrate lipid bilayers, but are thought to achieve net transfer of lipids between cytosolic leaflets of the donor and receiving membranes, they are expected to require the cooperation of scramblases to allow equilibration of lipid mass between the bilayer leaflets. Accordingly, there is evidence for the partnership of the chorein motif protein ATG2 with a lipid scramblase in the growth of the autophagosome membrane (4, 12, 13). Cooperation between VPS13A and XK, which has recently been confirmed by in vitro studies to have scramblase activity (14), would represent another example of such a partnership, providing clues to mechanisms of disease in chorea-acanthocytosis and McLeod syndrome. Strong support for this possibility came by the demonstration of an interaction between these two proteins: 1) studies of McLeod syndrome erythrocytes revealed that lack of XK results in a loss of VPS13A in their membranes (9), as expected if VPS13 and XK are part of the same complex; 2) their interaction was supported by biochemical experiments (9–11); and 3) the localization of overexpressed VPS13A at contacts between the endoplasmic reticulum (ER) and lipid droplets was shown to be abolished by cooverexpression of XK, resulting in a localization of VPS13A along with XK throughout the ER (10).So far, however, there has been no evidence from imaging studies in mammalian cells that VPS13A colocalizes with XK at the PM, where XK is expected to act. Studies in HeLa cells with tagged-VPS13A—both overexpressed VPS13A (10, 15–17) and VPS13A expressed at endogenous levels (15)—have shown that this protein is localized at contacts between the ER and mitochondria and lipid droplets. These studies have further shown that this localization of VPS13A is mediated by the interaction of its N-terminal region with the MSP domain of the ER protein VAP and of its C-terminal region with a yet to be defined binding site on mitochondria and on lipid droplets (15, 17). An interaction of VPS13A with mitochondria was also supported by the identification of this protein as a hit in a screen for mitochondria neighbors by proximity biotinylation (18, 19). Based on these findings, it has been proposed that VPS13A, like its paralog VPS13D, mediates transport of lipids to mitochondria, which are organelles not connected by vesicular transport to the ER, where most membrane lipids are synthesized (15, 20).The goal of this study was to determine how VPS13A interacts with XK and to determine whether such interaction can occur at the PM.     

Autosomal Recessive Spinocerebellar Ataxia Type 10: A Report of a New Case in Japan

Autosomal recessive spinocerebellar ataxia of type 10 (SCAR10) is a very rare neurodegenerative disease caused by mutations in the TMEM16K (ANO10) gene. This disorder is characterized by slowly progressive cerebellar ataxia and pyramidal signs inconstantly associated with cognitive decline, polyneuropathy, epilepsy, and vesicorectal dysfunction. To date, more than 40 cases have been reported in Europe. In contrast, only three cases have been identified in Asian countries. We herein report the third Japanese case of SCAR10 harboring a novel homozygous deletion mutation (c.616delG, p.Glu206Lysfs*17). This case presented with adult-onset slowly progressive spastic ataxia with cerebellar atrophy and mild cognitive decline.     

Brief Report: Adenosine A2A receptor blockade prevents cisplatin-induced impairments in neurogenesis and cognitive function

Chemotherapy-induced cognitive impairment (CICI) has emerged as a significant medical problem without therapeutic options. Using the platinum-based chemotherapy cisplatin to model CICI, we revealed robust elevations in the adenosine A_2A receptor (A_2AR) and its downstream effectors, cAMP and CREB, by cisplatin in the adult mouse hippocampus, a critical brain structure for learning and memory. Notably, A_2AR inhibition by the Food and Drug Administration–approved A_2AR antagonist KW-6002 prevented cisplatin-induced impairments in neural progenitor proliferation and dendrite morphogenesis of adult-born neurons, while improving memory and anxiety-like behavior, without affecting tumor growth or cisplatin’s antitumor activity. Collectively, our study identifies A_2AR signaling as a key pathway that can be therapeutically targeted to prevent cisplatin-induced cognitive impairments.     

Cytochrome 1A1 and 1B1 gene diversity in the Zanzibar islands

Amodiaquine (AQ) is a 4‐aminoquinoline widely used in the treatment of malaria as part of the artemisinin combination therapy (ACT). AQ is metabolised towards its main metabolite desethylamodiaquine mainly by cytochrome P450 2C8 (CYP2C8). CYP1A1 and CYP1B1 play a minor role in the metabolism but they seem to be significantly involved in the formation of the short‐lived quinine‐imine. To complete the genetic variation picture of the main genes involved in AQ metabolism in the Zanzibar population, previously characterised for CYP2C8, we analysed in this study CYP1A1 and CYP1B1 main genetic polymorphisms. The results obtained show a low frequency of the CYP1A1*2B/C allele (2.4%) and a high frequency of CYP1B1*6 (approximately 42%) followed by CYP1B1*2 (approximately 27%) in Zanzibar islands. Genotype data for CYP1A1 and CYP1B1 show a low incidence of fast metabolisers, revealing a relatively safe genetic background in Zanzibar’s population regarding the appearance of adverse effects.     

Brief Report: A distinct class of GTP-binding proteins mediates chloroplast protein import in Rhodophyta

Chloroplast protein import is mediated by translocons named TOC and TIC on the outer and inner envelope membranes, respectively. Translocon constituents are conserved among green lineages, including plants and green algae. However, it remains unclear whether Rhodophyta (red algae) share common chloroplast protein import mechanisms with the green lineages. We show that in the rhodophyte Cyanidioschyzon merolae, plastome-encoded Tic20_pt localized to the chloroplast envelope and was transiently associated with preproteins during import, suggesting its conserved function as a TIC constituent. Besides plastome-encoded FtsH_pt and several chaperones, a class of GTP (guanosine 5′-triphosphate)-binding proteins distinct from the Toc34/159 GTPase family associated transiently with preproteins. This class of proteins resides mainly in the cytosol and shows sequence similarities with Sey1/RHD3, required for endoplasmic reticulum membrane fusion, and with the periplastid-localized import factor PPP1, previously identified in the Apicomplexa and diatoms. These GTP-binding proteins, named plastid targeting factor for protein import 1 (PTF1) to PTF3, may act as plastid targeting factors in Rhodophyta.     

Genetic link with cholelithiasis among pediatric SCA Tunisian patients: Examples of UGT1A1, SLCO1A2 and SLCO1B1

Aims and background: Hyperbilirubinemia is often observed in chronic hemolysis and results in the formation of pigment cholelithiasis that could be increased by the presence of defected enzymes involved in the bilirubin metabolism. Indeed, this is the first report that interested in the study of polymorphisms in genes encoded for enzymes involved in the bilirubin metabolism: rs 4149056 of SLCO1B1 and rs4149000 of SLCO1A2 in combination with rs8175347 and rs887829 of UGT1A1 in order to find a correlation between the polymorphisms studied and the presence of gallstones in a population of sickle cell anemia (SCA) pediatric Tunisians.

Material and methods: Our study involved 102 unrelated Tunisian subjects. All SCA patients are children (less than 16 years old) and were characterized by hyperbilirubinemia and 52 of them have cholelithiasis. The polymorphisms of the candidate genes were analyzed for all subjects by PCR/sequencing. Genotype and allele frequencies between cases and controls were compared using Pearson's chi-square test with a significance threshold of P?<?0.05 (compare 2, version 1.02).

Results: The novelty of this report is that children carrying the combined genotype of the rs studied: (TA7TA7)/TT/TC/GA have a higher risk to develop gallstones (P?=?0.0027, RR?=?18.27 (20.0061–915.28)).

Conclusion: Altogether our data provide the implication of UGT1A1 and SLCO1A2 in sickle cell anemia-related cholelithiasis.     

HnRNP A2/B1及p21WAF1蛋白在非小细胞肺癌中表达及意义

目的探讨核内不均一核糖核蛋白A2/B1（hnRNP A2/B1）和p21WAF1蛋白在人非小细胞肺癌（NSCLC）组织中的表达,并进行相关性分析。方法采用免疫组化S-P法检测53例NSCLC组织、40例癌旁组织、7例肺良性病变组织中hnRNPA2/B1和p21WAF1表达。结果 NSCLC组织中hnRNP A2/B1和p21WAF12种蛋白的阳性表达率分别为66.0%和45.2%,显著高于癌旁肺组织和肺良性病变肺组织,差异有统计学意义（P〈0.05）。它们均与分化程度、淋巴结转移有关（P〈0.05）,与组织类型、临床分期无关（P〉0.05）。两种蛋白在NSCLC表达呈显著负相关（P=0.001）。结论 hnRNP A2/B1可能通过下调p21WAF1的表达而缩短细胞周期,促进NSCLC的癌细胞增殖。     

Alternating hemiplegia of childhood: a distinct clinical entity and ATP1A3-related disorders: A narrative review

Alternating Hemiplegia of Childhood (AHC) is a rare disorder with onset in the first 18 months of life characterized by stereotyped paroxysmal manifestations of tonic and dystonic attacks, nystagmus with other oculomotor abnormalities, respiratory and autonomic dysfunctions. AHC is often associated with epileptic seizures and developmental delay. Hemiplegic paroxysm is the most remarkable symptom, although AHC includes a large series of clinical manifestations that interfere with the disease course. No cure is available and the treatment involves many specialists and therapies. Flunarizine is the most commonly used drug for reducing the frequency and intensity of paroxysmal events. Mutations in ATP1A2, particularly in ATP1A3, are the main genes responsible for AHC. Some disorders caused by ATP1A3 variants have been defined as ATP1A3-related disorders, including rapid-onset dystonia-parkinsonism, cerebellar ataxia, pes cavus, optic atrophy, sensorineural hearing loss, early infant epileptic encephalopathy, child rapid-onset ataxia, and relapsing encephalopathy with cerebellar ataxia. Recently, the term ATP1A3 syndrome has been identified as a fever-induced paroxysmal weakness and encephalopathy, slowly progressive cerebellar ataxia, childhood–onset schizophrenia/autistic spectrum disorder, paroxysmal dyskinesia, cerebral palsy/spastic paraparesis, dystonia, dysmorphism, encephalopathy, MRI abnormalities without hemiplegia, and congenital hydrocephalus. Herewith, we discussed about historical annotations of AHC, symptoms, signs and associated morbidities, diagnosis and differential diagnosis, treatment, prognosis, and genetics. We also reported on the ATP1A3-related disorders and ATP1A3 syndrome, as 2 recently established and expanded genetic clinical entities.     

Erythrocyte membrane cholesterol and lipid core growth in a rabbit model of atherosclerosis: Modulatory effects of rosuvastatin

Background

Lipid core expansion is partly responsible for the conversion of a stable atherosclerotic lesion to a rupture-prone plaque. Intraplaque hemorrhage contributes to the accumulation of cholesterol within unstable plaques. In the present study, we investigated, using a rabbit model of atherosclerosis, the extent to which diet-induced increases in cholesterol content of erythrocyte membranes (CEM) contribute to lipid core expansion and the modulatory effect of rosuvastatin use.

Methods and results

Rabbits fed with atherogenic diet (0.75% cholesterol) for 5 months exhibited advanced atherosclerotic lesions (mean plaque area, 0.39 ± 0.03 mm²), and lipid core size was associated with the concentration–time integral (CTI) of CEM levels (r = 0.567, P = 0.004) independent of other established predictors of lipid core size. Further experiments were performed by feeding rabbits atherogenic diet (1% cholesterol) for 3 months, followed by either normal diet or normal diet plus rosuvastatin for the next 3 months. Although no differences were observed in total plaque area between both groups, administration of rosuvastatin was associated with significantly smaller lipid cores, fewer macrophages within the lipid core, less microvessels as well as with lower CTI of CEM levels compared to normal diet alone. Moreover, intraplaque erythrocyte membranes covered a smaller lipid core area in rabbits under rosuvastatin plus normal diet as opposed to rabbits under diet alone.

Conclusions

Increased CEM levels, induced by high-cholesterol diet, are associated with lipid core growth. Ingestion of a potent HMG-CoA reductase inhibitor (rosuvastatin) may decrease CEM levels, and this effect may contribute to regression of the lipid core.     

Brief Report: DARPP32, a target of hyperactive mTORC1 in the retinal pigment epithelium

The mechanistic target of rapamycin (mTOR) is assembled into signaling complexes of mTORC1 or mTORC2, and plays key roles in cell metabolism, stress response, and nutrient and growth factor sensing. Accumulating evidence from human and animal model studies has demonstrated a pathogenic role of hyperactive mTORC1 in age-related macular degeneration (AMD). The retinal pigment epithelium (RPE) is a primary injury site in AMD. In mouse models of RPE-specific deletion of Tuberous sclerosis 1 (Tsc1), which encodes an upstream suppressor of mTORC1, the hyperactivated mTORC1 metabolically reprogrammed the RPE and led to the degeneration of the outer retina and choroid (CH). In the current study, we use single-cell RNA sequencing (scRNA-seq) to identify an RPE mTORC1 downstream protein, dopamine- and cyclic AMP-regulated phosphoprotein of molecular weight 32,000 (DARPP-32). DARPP-32 was not found in healthy RPE but localized to drusen and basal linear deposits in human AMD eyes. In animal models, overexpressing DARPP-32 by adeno-associated virus (AAV) led to abnormal RPE structure and function. The data indicate that DARPP-32 is a previously unidentified signaling protein subjected to mTORC1 regulation and may contribute to RPE degeneration in AMD.     

Meeting Report: Ninth and Tenth Workshops of the European Paediatric Network for Haemophilia Management (PedNet)

This meeting report presents an overview of the discussions at the ninth and tenth workshops of the European Paediatric Network for Haemophilia Management (PedNet) that occurred in 2005 and 2006. Among numerous topics, a major theme of these workshops was the formation of inhibitors to replacement factor.     

Western Negev Mobile Diabetes Care Program: a model for interdisciplinary diabetes care in a semi-rural setting

We described a mobile diabetes clinic aimed to provide comprehensive, interdisciplinary care to patients with diabetes resident on a semi-rural area. A mobile, tertiary care diabetes clinic, composed of a diabetologist, a diabetes nurse-educator and a dietitian, was created. The clinic regularly visited the primary-care facilities of 3 towns of the Western Negev, a semi-rural area of southern Israel. A standardized, computer-based clinical protocol was applied. Analysis of data was performed on records of all patients who had had at least 2 visits to the clinic. Of 492 patients who met the inclusion criteria, 93.6% were diagnosed with type 2 diabetes, 58% were female, the mean age was 60 years and the mean time after diagnosis of diabetes was 10 years. Most patients had not visited a diabetes center before implementation of the mobile clinic. Parameters of clinical practice such as nutritional advice by a dietitian, interaction with a diabetes nurse-educator, performance of periodic ophthalmologic examination, and measurement of microalbumin excretion improved dramatically after opening of the mobile clinic. Modifiable clinical variables such as body mass index (p<0.05) blood pressures, fasting plasma glucose (p<0.001), hemoglobin A1c (p<0.01), LDL-cholesterol (p<0.01) and HDL-cholesterol (p<0.0001) improved significantly after implementation of the program. The implementation of a mobile diabetes care program in an area of low-density population is feasible. Significant improvement in parameters of clinical practice and of modifiable variables of diabetes control was achieved. The mobile diabetes clinic brought the interdisciplinary diabetes-care team to the patients' area of residence. Limited manpower answered the requirement of a geographically spread population. Received: 5 July 2001 / Accepted in revised form: 18 January 2002     

Brief Report: Prostaglandin production selectively in brain endothelial cells is both necessary and sufficient for eliciting fever

Fever is known to be elicited by prostaglandin E₂ acting on the brain, but its origin has remained disputed. We show in mice that selective deletion of prostaglandin synthesis in brain endothelial cells, but not in neural cells or myeloid cells, abolished fever induced by intravenous administration of lipopolysaccharide and that selective rescue of prostaglandin synthesis in brain endothelial cells reinstated fever. These data demonstrate that prostaglandin production in brain endothelial cells is both necessary and sufficient for eliciting fever.     

A protective role of a cholesteryl ester transfer protein gene variant towards ischaemic stroke in Sardinians

OBJECTIVES: Cholesteryl ester transfer protein (CETP) plays a key role in the metabolism of high-density lipoprotein (HDL), a strong, inverse, independent risk factor for cardiovascular disease. We sought to investigate the relationship between a common variant of CETP gene, the Taq1 B polymorphism, that has been previously associated with CETP blood concentrations, and the risk of ischaemic stroke in a genetically homogenous population from the Sardinia island, Italy. This population has been previously shown to be a highly conservative sample. DESIGN: A total of 215 cases of ischaemic stroke and 236 controls were selected and characterized for the CETP Taq1 B polymorphism. Allele and genotype frequencies were compared amongst cases and controls. RESULTS: Age, hypertension and hypercholesterolaemia were independent risk factors for stroke in this cohort. We found that presence of the CETP Taq1 B2 allele was associated with a significantly decreased risk of ischaemic stroke when assuming a recessive mode of inheritance (OR 0.55, 95% CI = 0.34-0.90, P = 0.017). This result was confirmed by multivariate analysis, after adjustment for age, presence of hypertension and hypercholesterolaemia (OR 0.53, 95% CI = 0.32-0.88, P = 0.014). By performing separate analysis for gender we found that the effect was present in females but not in males, with a significant sex-CETP gene variant interaction for both recessive (P = 0.005) and additive (P = 0.029) modes of inheritance. CONCLUSIONS: Our data suggest that the Taq1 B2 allelic variant of the CETP gene may be associated, as a protective factor, with occurrence of ischaemic stroke. Further studies are needed to further elucidate the clinical implications of our finding.     

血浆ApoB/ApoA1比值和D-二聚体水平的列线图模型对急性ST段抬高型心肌梗死患者PCI术后左心室血栓形成的预测价值

目的]分析血浆ApoB/ApoA1比值和D-二聚体(D-D)对急性ST段抬高型心肌梗死(STEMI)患者PCI术后左心室血栓形成(LVT)的预测价值,并建立列线图模型。 [方法]选取2021年1月─2022年12月阜阳市第六人民医院收治的187例STEMI患者。根据患者术后28天随访结果,将患者分为LVT组和非LVT组。对两组患者血浆ApoB/ApoA1比值和D-D水平等临床资料进行单因素和二元Logistic回归分析,探索STEMI患者PCI术后LVT形成的独立危险因素,建立列线图模型,并对列线图模型的诊断效能进行评价。 [结果]血浆ApoB/ApoA1比值升高(OR＝1.320,95%CI:1.057～1.648)、D-D水平增加(OR＝1.031,95%CI:1.020～1.042)、术前TIMI为0级(OR＝4.141,95%CI:1.018～16.849)及左心室射血分数(LVEF)降低(OR＝0.906,95%CI:0.853～0.963)是PCI术后LVT形成的独立危险因素(P＜0.05),上述指标预测LVT形成的AUC分别为0.792、0.800、0.623和0.726。基于以上指标建立列线图模型,ROC曲线分析表明,模型一致性指数为0.926,校正曲线显示该模型具有良好的区分度和一致性。 [结论]STEMI患者血浆ApoB/ApoA1比值升高和D-D水平增加与PCI术后LVT形成具有密切关系,基于上述指标建立的列线图模型对预测LVT有较高的诊断效能,有利于临床医务人员对高危患者的识别。     

Immunogenicity and reactogenicity of a combined hepatitis A/B candidate vaccine: first results

Abstract: We evaluated immunogenicity and reactogenicity of an inactivated, combined hepatitis A/B candidate vaccine in 50 seronegative volunteers. Each volunteer received a total of three doses of vaccine (720 EIU HAV and 20 μg HBs antigen) according to a 0, 1 and 6 month vaccination schedule. One month after the first injection, the seroconversion rate was 90% (45/50) for anti-HAV and 28% (14/50) for anti-HBs, respectively. After the booster dose, at month 7, the seroconversion rate was as high as 100% (49/49) for anti-HAV and 94% (46/49) for anti-HBs. The geometric mean titres increased with each dose of vaccine administered. Mild, and mostly local side effects were reported in 54% of the volunteers after the first injection and in less than 10% after the third injection. Our results show that this inactivated, candidate hepatitis A/B vaccine is highly immunogenic and well-tolerated.