Isolation and functional characterization of the C-terminus of rice phos-phatidylinositol 4-kinase in vitro

A partial rice (Oryza sativa L.) cDNA clone. OsPMK1c, was isolated through screening of a cDNA library constructed from tillering materials. OsPI4Klc encoded a peptide of 608 amino acids with a calculated molecular mass of 68.4 kDa. The OsPI4Klc peptide shared high homology and possessed the highly conserved domains present in most isolated cloned PI4-kinases, i.e. a lipid kinase unique (LKU) domain and a catalytic (CAT) domain. A region with similarity to pleckstrin homology (PH) domain was present in OsPI4K1c as well. Further comparison with genomic sequences in databases revealed that OsPI4K1c is located at the 3'-end of a putative rice PI 4-kinase coding gene OsPI4K1, and its coding region corresponded to the C-terminal half of OsPI4Kl protein. Twelve exons (49-562 bp in size) and 11 introns (77-974 bp in size) were identified in OsPI4K1c. The recombinant protein expressed in Escherichia coli phosphorylates phosphatidylinositol at the D4 position of the inositol ring. OsPI4K1 transcript levels were detected in a low but constitutive manner in shoot, stem, leaf, spike and root tissues and did not change upon treatment with different hormones, calcium and jasmonic acid (JA). However, treatment with salicylic acid (SA) elevated the mRNA level of the OsPI4K1 gene, which suggested the involvement of OsPI4K1 in wounding responses.

Phosphoinositide-3-kinase regulatory subunit 4 participates in the occurrence and development of amyotrophic lateral sclerosis by regulating autophagy

The development of amyotrophic lateral sclerosis(ALS)may be related to the abnormal alterations of multiple proteins.Our previous study revealed that the expression of phosphoinositide-3-kinase regulatory subunit 4(PIK3R4)was decreased in ALS.However,the role of PIK3R4 in ALS pathogenesis remains unknown.This study was the first to find that transfection of PC12 cells with small interfering RNA against the PIK3R4 gene significantly decreased the expression levels of PIK3R4 and the autophagy-related proteins p62 and LC3.Additionally,in vivo experiments revealed that the PIK3R4 protein was extensively expressed in the anterior horn,posterior horn,central canal,and areas surrounding the central canal in cervical,thoracic,and lumbar segments of the spinal cord in adult mice.PIK3R4 protein was mainly expressed in the neurons within the spinal lumbar segments.PIK3R4 and p62 expression levels were significantly decreased at both the pre-onset and onset stages of ALS disease in Tg(SOD1*G93A)1 Gur mice compared with control mice,but these proteins were markedly increased at the progression stage.LC3 protein expression did not change during progression of ALS.These findings suggest that PIK3R4 likely participates in the prevention of ALS progression.This study was approved by the Ethics Committee for Animal Care and Use of Jiangxi Provincial People’s Hospital,Affiliated People’s Hospital of Nanchang University(approval No.2020025)on March 26,2020.

Phosphatidylinositol 4-kinase β mutations cause nonsyndromic sensorineural deafness and inner ear malformation

Congenital hearing loss is a common disorder worldwide.Heterogeneous gene variation accounts for approximately 20-25%of such patients.We investigated a five-generation Chinese family with autosomaldominant nonsyndromic sensorineural hearing loss(SNHL).No wave was detected in the pure-tone audiometry,and the auditory brainstem response was absent in all patients.Computed tomography of the patients,as well as of two sporadic SNHL cases,showed bilateral inner ear anomaly,cochlear maldevelopment,absence of the osseous spiral lamina,and an enlarged vestibular aqueduct.Such findings were absent in nonaffected persons.We used linkage analysis and exome sequencing and uncovered a heterozygous missense mutation in the PI4 KB gene(p.Gln121 Arg)encoding phosphatidylinositol 4-kinaseβ(PI4 KB)from the patients in this family.In addition,3 missense PI4 KB(p.Val434 Gly,p.Glu667 Lys,and p.Met739 Arg)mutations were identified in five patients with nonsyndromic SNHL from 57 sporadic cases.No such mutations were present within 600 Chinese controls,the 1000 genome project,gnom AD,or similar databases.Depleting pi4 kb m RNA expression in zebrafish caused inner ear abnormalities and audiosensory impairment,mimicking the patient phenotypes.Moreover,overexpression of 4 human missense PI4 KB mutant m RNAs in zebrafish embryos resulted in impaired hearing function,suggesting dominant-negative effects.Taken together,our results reveal that PI4 KB mutations can cause SNHL and inner ear malformation.PI4 KB should be included in neonatal deafness screening.

A gene encoding AtPIP5K2 may be involved in regulating the sensitivity to osmotic stress

One mutant line eto with salt tolerance was screened from a T-DNA insertion mutant collection of Arabidopsis thaliana. In addition to a reduced rate of seed germination, NaCl and ABA also inhibited the growth and the greening of cotyledons of wild-type seedlings, but not the eto mutant. TAIL-PCR analysis showed that T-DNA tag insertion in the eto was located at nucleotide 27,502 in BAC F3M18, upstream （at position -487 relative to the translation initiation codon） of gene At lg77740 （encoding a putative phosphatidylinositol-4-phosphate 5-kinase, AtPIP5K2）. This inserted mutation cosegregated closely with the eto phenotype, Another analysis not only indicated that AtPIP5K2 transcript is expressed predominantly in roots and rosette leaves, but also showed the T-DNA insertion resulted higher accumulation of the AtPIP5K2 in eto mutant plants and did not influenced the expression of the upstream At lg77730 gene. This change may play an essential role in the tolerance of eto mutant plant to the osmotic stress.

Heme oxygenase 1-mediated ferroptosis in Kupffer cells initiates liver injury during heat stroke

With the escalating prevalence of global heat waves,heat stroke has become a prominent health concern,leading to substantial liver damage.Unlike other forms of liver injury,heat strokeinduced damage is characterized by heat cytotoxicity and heightened inflammation,directly contributing to elevated mortality rates.While clinical assessments have identified elevated bilirubin levels as indicative of Kupffer cell dysfunction,their specific correlation with heat stroke liver injury remains unclear.Our hypothesis proposes the involvement of Kupffer cell ferroptosis during heat stroke,initiating IL-1bmediated inflammation.Using single-cell RNA sequencing of murine macrophages,a distinct and highly susceptible Kupffer cell subtype,Clec4Ft/CD206t,emerged,with heme oxygenase 1(HMOX-1)playing a pivotal role.Mechanistically,heat-induced HMOX-1,regulated by early growth response factor 1,mediated ferroptosis in Kupffer cells,specifically in the Clec4F t/CD206 t subtype(KC2),activating phosphatidylinositol 4-kinase beta and promoting PI4P production.This cascade triggered NLRP3 inflammasome activation and maturation of IL-1b.These findings underscore the critical role of targeted therapy against HMOX-1 in ferroptosis within Kupffer cells,particularly in Clec4F t/CD206 t KCs.Such an approach has the potential to mitigate inflammation and alleviate acute liver injury in the context of heat stroke,offering a promising avenue for future therapeutic interventions.

葛根芩连汤对KKAy糖尿病小鼠TLR4/IKKβ/NF-κB信号通路的影响

目的:观察经方葛根芩连汤对KKAy小鼠部分炎性因子及脂多糖介导的炎症通路中关键靶点的影响,探讨其改善2型糖尿病的作用机制。方法:选取SPF级自发性2型糖尿病动物模型KKAy小鼠65只及对照C57BL/6J小鼠13只予屏障系统、高脂饲料喂养,随机血糖≥13.9 mmoL·L^(-1),为成模小鼠44只。随机分为5组,每组11只。正常组(生理盐水20 mL·kg^(-1))、阿卡波糖组(3.9 mg·kg^(-1))、葛根芩连汤高、低剂量组(1.82、0.45 g·kg^(-1))及模型组(生理盐水20 mL·kg^(-1)),连续灌胃给药8周,1次/d,系统评价血糖及体质量。末次给药12 h后,摘眼球取血,提取血清及肌肉、肝脏组织。采用半定量酶联免疫吸附测定法(ELISA)检测炎性因子肿瘤坏死因子-α(TNF-α)、白细胞介素-6(IL-6)及葡萄糖转运子4(GluT4)含量,蛋白免疫印迹法(Western blot)检测肌肉组织IκB磷酸化激酶β(IKKβ)蛋白、核转录因子-κB(NF-κB)及肝组织Toll样受体4(TLR4)蛋白表达水平。结果:与正常组比较,模型组体质量及血糖显著升高(P<0.01);与模型组比较,阿卡波糖组及葛根芩连汤组能够明显降低体质量及血糖水平(P<0.05,P<0.01)。ELISA结果显示,与正常组比较,模型组炎性因子TNF-α、IL-6含量显著升高(P<0.01),GluT4含量明显下降(P<0.05);与模型组比较,各给药组炎性因子TNF-α、IL-6含量均有不同程度下降(P<0.05,P<0.01),阿卡波糖组与葛根芩连汤高剂量组GluT4含量明显升高(P<0.05,P<0.01)。Western blot分析显示,与正常组比较,模型组IKKβ、NF-κB及TLR4蛋白表达均有升高(P<0.01);与模型组比较,阿卡波糖组与葛根芩连汤组IKKβ、NF-κB及TLR4蛋白表达均明显下降(P<0.05,P<0.01)。结论:葛根芩连汤可能在调节肠道菌群的基础上,通过下调TLR4通路中关键炎性因子的水平,抑制其激活,提高GluT4的转位及活性水平,从而在一定程度上抑制炎性级联效应,改善2型糖尿病。

ANXA2 Facilitates Enterovirus 71 Infection by Interacting with 3D Polymerase and PI4KB to Assist the Assembly of Replication Organelles

Similar to that of other enteroviruses, the replication of enterovirus 71(EV71) occurs on rearranged membranous structures called replication organelles(ROs). Phosphatidylinositol 4-kinase Ⅲ(PI4KB), which is required by enteroviruses for RO formation, yields phosphatidylinositol-4-phosphate(PI4P) on ROs. PI4P then binds and induces conformational changes in the RNA-dependent RNA polymerase(Rd Rp) to modulate Rd Rp activity. Here, we targeted 3D polymerase, the core enzyme of EV71 ROs, and found that the host factor Annexin A2(ANXA2) can interact with 3 D polymerase and promote the replication of EV71. Then, an experiment showed that the annexin domain of ANXA2, which possesses membranebinding capacity, mediates the interaction of ANXA2 with EV71 3 D polymerase. Further research showed that ANXA2 is localized on ROs and interacts with PI4KB. Overexpression of ANXA2 stimulated the formation of PI4P, and the level of PI4P was decreased in ANXA2-knockout cells. Furthermore, ANXA2, PI4KB, and 3D were shown to be localized to the viral RNA replication site, where they form a higher-order protein complex, and the presence of ANXA2 promoted the PI4 KB-3D interaction. Altogether, our data provide new insight into the role of ANXA2 in facilitating formation of the EV71 RNA replication complex.

Dual inhibition of EGFR at protein and activity level via combinatorial blocking of PI4KIla as anti-tumor strategy

Our previous studies indicate that phosphatidylinositol 4-kinase Ila can promote the growth of multi-malignant tumors via HER-2/PI3K and MAPK pathways. However, the molecular mechanisms of this pathway and its potential for clinical application remain unknown. In this study, we found that PI4KIla could be an ideal combinatorial target for EGFR treatment via regulating EGFR degradation. Results showed that PI4KIla knockdown reduced EGFR protein level, and the expression of Pi4KIla shows a strong correlation with EGFR in human breast cancer tissues （r= 0.77, P 〈 0.01）. PI4KIla knockdown greatly prolonged the effects and decreased the effective dosage of AG-1478, a specific inhibitor of EGFR. In addition, it significantly enhanced AG1478-induced inhibition of tumor cell survival and strengthened the effect of the EGFR-targeting anti-cancer drug Iressa in xenograft tumor models. Mechanistically, we found that PI4KIla suppression increased EGFR ligand-independent degradation. Quantitative proteomic analysis by stable isotope labeling with amino acids in cell culture （SlLAC） and LC-MS/MS suggested that HsPg0 mediated the effect of PI4KIla on EGFR. Furthermore, we found that combined inhibition of PI4KIla and EGFR suppressed both PI3K/AKT and MAPK/ERK pathways, and resulted in downregulation of multiple oncogenes like PRDX2, FASN, MTA2, ultimately leading to suppression of tumor growth. Therefore, we conclude that combined inhibition of PI4KIla and EGFR exerts a multiple anti-tumor effect. Dual inhibition of EGFR at protein and activity level via combinatorial blocking of PI4KIla presents a novel strategy to combat EGFR-dependent tumors.

Association of the phosphatidylinositol signal pathway with prolonged myocardial ischemia

OBJECTIVE: To study the changes in activity of phosphatidylinositol 4 kinase (PI 4 kinase), phosphatidylinositol 4 phosphate 5 kinase (PIP 5 kinase) and protein kinase C (PKC) during myocardial ischemia and elucidate the relationship between phosphatidylinositol signal pathways and prolonged myocardial ischemia. METHODS: In vivo an ischemic rat model was used. Activity of PI 4 kinase, PIP 5 kinase and PKC were measured at different times in postischemic heart cells using isotope analysis. RESULTS: The activity of PI kinase, PIP kinase and PKC in the myocardium increased to peak at 1 hour postischemia, with activities 6.1, 3.0 and 4.0 fold over control levels, respectively. Their activities declined to normal levels with time. CONCLUSION: The phosphatidylinositol signal pathway is involved in prolonged myocardial ischemia, but its mechanism needs further study.

Functional Cooperativity of Enzymes of Phosphoinositide Conversion According to Synergistic Effects on Pectin Secretion in Tobacco Pollen Tubes

The Arabidopsis phosphoinositide kinases PI4Kβ1 and PIP5K5 have been implicated in the control of directional vesicle trafficking underlying polar tip growth in pollen tubes. PI4Kβ1 and PIP5K5 catalyze key consecutive steps of phosphoinositide conversion, and it appears obvious that phosphatidylinositol-4-phosphate formed by PI4Kβ1 might act as a substrate for phosphatidylinositol-4,5-bisphosphate formation by PIP5K5. However, this hypothesis has not been experimentally addressed and distinct localization patterns of PI4Kβ1, PIP5K5, and also PI-synthases （PIS） generating phosphatidylinositol suggest additional complexity. Here, the synergistic functionality of enzymes of phosphoinositide conversion was assessed. In tobacco and Arabidopsis pollen tubes, phosphoinositides influence the apical secretion of pectin, and increased pectin deposition results in characteristic morphological alterations. Catalytically active and dominant negative variants of PI4Kβ1 and PIP5K5 were systematically co-expressed in tobacco pollen tubes and the incidence of morphologies related to enhanced pectin secretion was evaluated. The data support a proposed functional interplay of PI4Kβ1 and PIP5K5 at the trans-Golgi network, mediating directional vesicle trafficking. Co-expression experiments additionally including PIS isoforms, PIS1 or PIS2, indicate that pectin secretion is synergistically mediated by PI4Kβ1 and PIPSK5 acting on Ptdlns formed by PIS2 rather than PIS1. Possible ramifications for the preferential channeling of phosphoinositide intermediates between particular isoforms of PI pathway enzymes are discussed.