巨噬细胞迁移抑制因子分子机制研究进展

巨噬细胞迁移抑制因子（macrophage migration inhibitory factor, MIF）是一类多效性的前炎症细胞因子,能够促进其他多种前炎症因子的分泌或表达。其基因在大多数哺乳动物基因组中具有90%的同源性。MIF启动子区含有能够与多种转录因子结合的DNA结合位点,同时含有与其表达水平相关的多态性位点。MIF发挥其生物学功能,一方面可以通过非受体介导的内吞作用,实现MIF与c-Jun激活结构域结合蛋白-1（JAB1）的相互作用;另一方面,受体依赖型的MIF能够激活包括PI3K/AKT、MAPK和G蛋白偶联受体相关的信号传导途径等。此外,MIF还能够通过直接或间接方式调节肿瘤抑制基因p53的功能。MIF已经被证实参与调解炎症、肿瘤生成和纤维化等生物学过程。从MIF表达、相关受体、涉及的信号通路与生物学过程等方面,对其分子功能的研究进展进行了总结,并对MIF相关的分子机理进行了综述,旨在为MIF相关疾病的诊断和治疗提供线索。     

肿瘤坏死因子受体生物学功能及其临床应用研究进展

肿瘤坏死因子（Tumor necrosis factor,TNF）的生物学功能是由其受体（TNF receptor,TNFR）介导的,可溶性TNF受体（Soluble TNF receptor,sTNRF）从膜上脱萍下来,不再负责信号传递,但能与TNF结合,中和TNF的生物学活性。sTNFR与IgG Fc组成的嵌合蛋白能有效治疗成人类风湿性关节炎和几童多发性关节炎,对其他与TNF相关免疫性疾病的治疗目前正在处于临床研究阶段。     

Jak—STAT信号传递途径

细胞因子是一类具有重要生物学功能的蛋白因子。它们是通过细胞表面的受体介导其生物学效应的。配体和受体蛋白结合,迅速导致与受体蛋白结合着的Janus酪氨酸激酶(Jak)的活化,同时触发信号传导和转录激活因子(Signal Transducer and Activator of Tran-     

白介素18结合蛋白研究进展

白介素18结合蛋白（IL-18BP）是一种新近发现的蛋白因子,具有胞外Ig样受体结构特征,并与某些病毒编码的蛋白有较高的同源性,它能与IL-18特异性结合并阻断其相关的生物学功能。由于其在免疫调控及免疫预防方面的特殊作用而受到广泛关注。     

血清APN、PGRN联合检测对脓毒症患儿疾病的预测价值及与其预后的相关性分析

摘要 目的：研究脂联素（APN）和颗粒体上皮蛋白前体（PGRN）在脓毒症患儿血清中的变化,并探讨其临床意义。方法：纳入2019年1月到2021年6月在我院接受治疗的脓毒症患儿90例,并纳入同期在我院进行体检的健康儿童30例作为对照组。根据脓毒症患儿预后将其分为存活组（n=67）和死亡组（n=23）。采集所有研究对象外周血,通过酶联免疫吸附剂测定测定血清APN、PGRN、肿瘤坏死因子α（TNF-α）、白介素1β（IL-1β）、C-反应蛋白（CRP）和降钙素原（PCT）。分析血清APN、PGRN与脓毒症患儿血清炎症因子、疾病严重程度的相关性。结果：脓毒症患儿血清APN、PGRN均显著低于对照组健康儿童（P<0.05）。在脓毒症患儿中,血清APN、PGRN与血清TNF-α、IL-1β、CRP以及PCR含量均呈负相关（P<0.05）。存活组脓毒症患儿血清APN、PGRN以及小儿危重病例评分（PCIS）均显著高于死亡组脓毒症患儿（P<0.05）,并且脓毒症患儿血清APN、PGRN与PCIS评分呈正相关。多因素Logstic回归分析结果显示：小儿危重病例评分表（PCIS）评分（OR=2.691,95%CI=1.052-4.352）、血清APN（OR=3.026,95%CI=1.628-4.692）和PGRN（OR=2.824,95%CI=1.328-6.824）水平均是影响脓毒症患儿预后的独立危险因素（P<0.05）。结论：脓毒症患儿血清APN、PGRN均显著降低,其含量与脓毒症疾病严重程度和外周血炎症反应具有相关性。     

黑素皮质素受体-2基因表达调控相关因子研究进展

黑素皮质素受体-2（melanoeortin2-receptor,MC2R）属于A类七个跨膜α螺旋G蛋白受体,具有通过CA／cAMP／PKA信号转导途径调节类固醇激素分泌的昼夜节律和应激引起变化的功能。MC2R基因表达障碍可导致一种常染色体隐性遗传疾病,即家族性糖皮质激素缺陷（FGD）。黑素皮质素受体-2（melanocortin2-receptor,MC2R）基因在特定组织中是否表达,表达丰度的高低是由多种调控因子相互作用决定的。本文就参与其表达调控的类固醇转录因子-1（steroidogenic factor-1,SF-1）、过氧化物增值物激活受体γ（PPARγ）、视黄酸X受体α（RXRα）、活化激活蛋白1（activatorproteinl,AP-1）DAX-1（dosage-sensitive sexreversal adrenal hypoplasia gene on the X chromosome,gene-1）和E-盒结合蛋白等因子做一综述。     

载脂蛋白M

载脂蛋白M(apoM)是一类在血液中主要与高密度脂蛋白（HDL）结合的载脂蛋白,呈组织特异性表达且有着众多生物学功能.体内外多种因素可从转录或转录后水平对其表达进行调控:肝细胞核因子-1α,4α（HNF-1α,4α）、肝受体同系物-1（LRH-1）、叉头框转录因子a2（Foxa2）、血小板活化因子（PAF）等可上调其表达;肝X受体（LXR）、维甲酸X受体（RXR）、法尼酯X受体（FXR）、小异源二聚体-1(SHP-1)以及绝大多数细胞因子可下调其表达,具体调节机制复杂. 结构上,apoM含有一个特征性的疏水性信号肽,可结合1 磷酸鞘氨醇（S1P）等小的生物活性脂,以此介导多项生命活动. 功能上,apoM能促进preβ-HDL的生成,并提高其一系列抗动脉粥样硬化的生物活性,如胆固醇逆向转运、抗炎、以及低密度脂蛋白（LDL）的抗氧化等.在一些糖尿病病人体内,apoM的含量也显著降低,而apoM含量的提高可以降低血糖含量,增加胰岛素分泌以及改善胰岛素抵抗,不少学者将其视为该病发生发展的一项预测指标.本文就近年来对apoM的生物学特性,特别是其表达调控机制和功能的研究进展进行综述.     

应用酵母双杂交系统筛选hTNFα特异性结合肽

肿瘤坏死因子（TNFα）是一种多功能细胞因子,目前已知许多病理性反应与之有关,如类风湿性关节炎、脓毒性休克、慢性心衰等。TNF的生物学功能是通过结合到细胞表面相应的受体（TNFR）来实现的,因此在炎症区引入可溶性TNF受体或TNF抗体,与膜上受体竞争性结合TNF,可以抑制TNF介导的生物学活性。在临床上,Enbrel、Infliximab和eralizumab等TNF拮抗剂,     

前列腺素核受体系统信号转导及基因表达调控

脂肪酸和前列腺素等脂代谢的产物不仅通过膜受体起作用,也可以通过与核受体结合来调节基因表达.前列腺素I₂(PGI₂)既可以与G蛋白偶联的细胞表面IP受体起作用,也可以通过核受体过氧化物酶体增殖因子活化受体（PPARs）发挥生物学功能.前列腺素E₂(PGE₂)的受体（EPs）不仅仅在质膜上有,最近在核膜上也发现了EPs受体.前列腺素核受体介导的信号转导途径与膜受体介导的信号途径不同,对于基因转录的调控机制也不同.     

泛素化在TRAF2介导的NF-κB信号通路中的作用

NF-κB（核因子κ增强子结合蛋白）是核转录因子家族成员,具有调节免疫、炎症和细胞存活的功能.它可被TRAF2（tumor necrosis factor receptor associated factor 2,肿瘤坏死因子受体相关因子2）等相关因子活化.TRAF2包含了N-端的环指结构域和C-端的高度保守结构域.它通过与肿瘤坏死因子受体超家族成员相互作用,介导了下游信号通路.而TRAF2的泛素化在过程中是关键的,鞘磷脂作为TRAF2的泛素化连接酶辅助因子,在TRAF2介导的NF-κB信号通路中发挥重要作用.     

Modified Yeast-Two-Hybrid System to Identify Proteins Interacting with the Growth Factor Progranulin

Progranulin (PGRN), also known as granulin epithelin precursor (GEP), is a 593-amino-acid autocrine growth factor. PGRN is known to play a critical role in a variety of physiologic and disease processes, including early embryogenesis, wound healing ¹, inflammation ^{2, 3}, and host defense ⁴. PGRN also functions as a neurotrophic factor ⁵, and mutations in the PGRN gene resulting in partial loss of the PGRN protein cause frontotemporal dementia ^{6, 7}. Our recent studies have led to the isolation of PGRN as an important regulator of cartilage development and degradation ^8-11. Although PGRN, discovered nearly two decades ago, plays crucial roles in multiple physiological and pathological conditions, efforts to exploit the actions of PGRN and understand the mechanisms involved have been significantly hampered by our inability to identify its binding receptor(s). To address this issue, we developed a modified yeast two-hybrid (MY2H) approach based on the most commonly used GAL4 based 2-hybrid system. Compared with the conventional yeast two-hybrid screen, MY2H dramatically shortens the screen process and reduces the number of false positive clones. In addition, this approach is reproducible and reliable, and we have successfully employed this system in isolating the binding proteins of various baits, including ion channel ¹², extracellular matrix protein ^{10, 13}, and growth factor¹⁴. In this paper, we describe this MY2H experimental procedure in detail using PGRN as an example that led to the identification of TNFR2 as the first known PGRN-associated receptor ^{14, 15}.     

The granulin gene family: from cancer to dementia

The growth factor progranulin (PGRN) regulates cell division, survival, and migration. PGRN is an extracellular glycoprotein bearing multiple copies of the cysteine‐rich granulin motif. With PGRN family members in plants and slime mold, it represents one of the most ancient of the extracellular regulatory proteins still extant in modern animals. PRGN has multiple biological roles. It contributes to the regulation of early embryogenesis, to adult tissue repair and inflammation. Elevated PGRN levels often occur in cancers, and PGRN immunotherapy inhibits the growth of hepatic cancer xenografts in mice. Recent studies have demonstrated roles for PGRN in neurobiology. An autosomal dominant mutation in GRN, the gene for PGRN, leads to neuronal atrophy in the frontal and temporal lobes, resulting in the disease frontotemporal lobar dementia. In this review we will discuss current knowledge of the multifaceted biology of PGRN.     

Sorting out frontotemporal dementia?

Mutations within the granulin (GRN) gene that encodes progranulin (PGRN) cause the neurodegenerative disease frontotemporal lobar degeneration with ubiquitin inclusions (FTLD-U). The receptor for PGRN in the CNS has not been previously identified. In this issue of Neuron, Hu and colleagues identify Sortilin (SORT1) as a key neuronal receptor for PGRN that facilitates its endocytosis and regulates PGRN levels in?vitro and in?vivo.     

Serum progranulin levels are elevated in patients with systemic lupus erythematosus, reflecting disease activity

Introduction

Progranulin (PGRN) is the precursor of granulin (GRN), a soluble cofactor for toll-like receptor 9 (TLR9) signaling evoked by oligonucleotide (CpG)-DNA. Because TLR9 signaling plays an important role in systemic lupus erythematosus (SLE), we investigated whether PGRN is involved in the pathogenesis of SLE.

Methods

We measured concentrations of serum PGRN and interleukin-6 (IL-6) with enzyme-linked immunosorbent assay (ELISA) in patients with SLE (n = 68) and in healthy controls (n = 60). We assessed the correlation between the serum PGRN levels and established disease-activity indexes. The sera from the patients with high PGRN titers (>80 ng/ml) at the initial evaluation were reevaluated after the disease was ameliorated by treatment. We also measured the IL-6 concentration secreted by peripheral blood mononuclear cells (PBMCs) incubated with (a) oligonucleotide (CpG-B) in the presence or absence of recombinant human PGRN (rhPGRN); and (b) lupus sera in the presence or absence of a neutralizing anti-PGRN antibody.

Results

Serum PGRN levels were significantly higher in SLE patients than healthy controls. Their levels were significantly associated with activity of clinical symptoms. They also significantly correlated with values of clinical parameters, including the SLE Disease Activity Index and anti-double-stranded DNA antibody titers, and inversely with CH50, C3, and C4 levels. Moreover, serum PGRN levels significantly decreased after successful treatment of SLE. The rhPGRN significantly upregulated the production of IL-6 by PBMCs stimulated with CpG-B. Patients' sera stimulated production of IL-6 from PBMCs, which was significantly impaired by neutralization of PGRN. The serum PGRN levels significantly correlated with the serum IL-6 levels.

Conclusions

Serum PGRN could be a useful biomarker for disease activity of SLE. PGRN may be involved in the pathogenesis of SLE partly by enhancing the TLR9 signaling.     

Progranulin: a promising therapeutic target for rheumatoid arthritis

Progranulin (PGRN) is an autocrine growth factor with multiple functions. This review provides updates about the interplays of PGRN with extracellular matrix proteins, proteolytic enzymes, inflammatory cytokines, and cell surface receptors in cartilage and arthritis, with a special focus on the interaction between PGRN and TNF receptors (TNFR) and its implications in inflammatory arthritis. The paper also highlights Atsttrin, an engineered protein composed of three PGRN fragments that prevents inflammation in several inflammatory arthritis models. Identification of PGRN as a ligand of TNFR and an antagonist of TNFα signaling, together with the discovery of Atsttrin, not only betters our understanding of the pathogenesis of arthritis, but also provides new therapeutic interventions for various TNFα-mediated pathologies and conditions, including rheumatoid arthritis.     

Progranulin is required for proper ER stress response and inhibits ER stress-mediated apoptosis through TNFR2

Progranulin (PGRN) was reported to be a stress-response factor in response to hypoxia and acidosis. Here we present evidences demonstrating that PGRN is also an endoplasmic reticulum (ER) stress responsive factor: PGRN expression was induced and its activation of Erk1/2 and Akt signaling enhanced in response to ER stress; Normal ER stress response was lost in PGRN deficient cells and PGRN deficient cells became hypersusceptible to ER stress-induced apoptosis; additionally, recombinant PGRN could rescue the defects in ER-stress responses seen in PGRN deficient cells. Mechanistic studies indicated that PGRN/TNFR2 was critical for PGRN mediated regulation of ER stress response: similar to PGRN, the expression of TNFR2, but not TNFR1, was also induced in the course of ER stress; in addition, the association between PGRN and TNFR2 was markedly enhanced following ER stress; More importantly, PGRN protection of ER stress induced apoptosis was abolished when TNFR2 signaling was blocked. In addition, the 2nd and 3rd cysteine-rich domains (CRD) in the extracellular portion of TNFR2 (CRD2CRD3), known to directly bind to PGRN, disturbed the interaction of PGRN with TNFR2, and in turn abolished PGRN-mediated activation of Erk1/2 and Akt signaling and protection against apoptosis in response to ER-stress. Collectively, PGRN plays an important role in ER stress and regulates ER stress response through interacting with TNFR2. This study provides new insight into PGRN regulation of stress response and may also present PGRN as a potential molecular target for treating stress-associated disorders.     

Progranulin regulates neuronal outgrowth independent of Sortilin

ABSTRACT: BACKGROUND: Progranulin (PGRN), a widely secreted growth factor, is involved in multiple biological functions, and mutations located within the PGRN gene (GRN) are a major cause of frontotemporal lobar degeneration with TDP-43-positive inclusions (FLTD-TDP). In light of recent reports suggesting PGRN functions as a protective neurotrophic factor and that sortilin (SORT1) is a neuronal receptor for PGRN, we used a Sort1-deficient (Sort1/) murine primary hippocampal neuron model to investigate whether PGRN's neurotrophic effects are dependent on SORT1. We sought to elucidate this relationship to determine what role SORT1, as a regulator of PGRN levels, plays in modulating PGRN's neurotrophic effects. RESULTS: As the first group to evaluate the effect of PGRN loss in Grn knockout primary neuronal cultures, we show neurite outgrowth and branching are significantly decreased in Grn/ neurons compared to wild-type (WT) neurons. More importantly, we also demonstrate that PGRN overexpression can rescue this phenotype. However, the recovery in outgrowth is not observed following treatment with recombinant PGRN harboring missense mutations p.C139R, p.P248L or p.R432C, indicating that these mutations adversely affect the neurotrophic properties of PGRN. In addition, we also present evidence that cleavage of fulllength PGRN into granulin peptides is required for increased neuronal outgrowth, suggesting that the neurotrophic functions of PGRN are contained within certain granulins. To further characterize the mechanism by which PGRN impacts neuronal morphology, we assessed the involvement of SORT1. We demonstrate that PGRN induced-outgrowth occurs in the absence of SORT1 in Sort1/ cultures. CONCLUSION: We demonstrate that loss of PGRN impairs proper neurite outgrowth and branching, and that exogenous PGRN alleviates this impairment. Furthermore, we determined that exogenous PGRN induces outgrowth independent of SORT1, suggesting another receptor(s) is involved in PGRN induced neuronal outgrowth.     

Progranulin Facilitates Conversion and Function of Regulatory T Cells under Inflammatory Conditions

The progranulin (PGRN) is known to protect regulatory T cells (Tregs) from a negative regulation by TNF-α, and its levels are elevated in various kinds of autoimmune diseases. Whether PGRN directly regulates the conversion of CD4+CD25-T cells into Foxp3-expressing regulatory T cells (iTreg), and whether PGRN affects the immunosuppressive function of Tregs, however, remain unknown. In this study we provide evidences demonstrating that PGRN is able to stimulate the conversion of CD4+CD25-T cells into iTreg in a dose-dependent manner in vitro. In addition, PGRN showed synergistic effects with TGF-β1 on the induction of iTreg. PGRN was required for the immunosuppressive function of Tregs, since PGRN-deficient Tregs have a significant decreased ability to suppress the proliferation of effector T cells (Teff). In addition, PGRN deficiency caused a marked reduction in Tregs number in the course of inflammatory arthritis, although no significant difference was observed in the numbers of Tregs between wild type and PGRN deficient mice during development. Furthermore, PGRN deficiency led to significant upregulation of the Wnt receptor gene Fzd2. Collectively, this study reveals that PGRN directly regulates the numbers and function of Tregs under inflammatory conditions, and provides new insight into the immune regulatory mechanism of PGRN in the pathogenesis of inflammatory and immune-related diseases.     

异位（过）表达PGRN抑制IL-1β引起的髓核细胞损伤

炎症因子IL-1β是引起髓核细胞功能异常的关键因素之一。颗粒体蛋白原（progranulin,PGRN）是一种多功能生长因子,在组织修复、炎症反应等过程中发挥重要作用,但其在髓核细胞中的作用尚不清楚。本研究以IL-1β诱导的髓核细胞炎性损伤模型为研究对象,探讨PGRN对IL 1β诱导的髓核细胞损伤的保护作用及其机制。基因转染结合MTT方法证明,与IL-1β处理的细胞比较,过表达PGRN可逆转IL-1β引起的原代培养的髓核细胞生长抑制,促进细胞增殖。TUNEL技术和流式细胞分析显示,PGRN抑制IL-1β诱导的髓核细胞凋亡。Western印迹和RT-qPCR方法揭示,与IL-1β处理的细胞相比,过表达PGRN显著上调聚蛋白聚糖（aggrecan）和II型胶原（collagen type II）的蛋白质表达,但下调基质金属蛋白酶-13（MMP-13）、分解素-金属蛋白酶ADAMTS-5的表达,同时抑制IL-1β诱导的炎性因子IL-6、IL-8和TNF-α的表达,说明PGRN可缓解IL-1β引起的炎性反应,并减少细胞外基质（ECM）相关蛋白质的降解。此外,过表达PGRN还可降低p65、p-IkB a和β-catenin的蛋白质表达水平,提示PGRN可抑制IL-1β下游TNF-α介导的NF-κB信号途径及β-catenin途径。总之,上述结果提示,过表达PGRN可通过抑制IL-1β诱导的炎性反应、髓核细胞凋亡及基质代谢紊乱,缓解IL-1β诱导的髓核细胞损伤;PGRN的这种抗炎、抗基质降解作用可能与PGRN参与调控NF-κB和β-catenin信号途径有关。     

Prosaposin facilitates sortilin-independent lysosomal trafficking of progranulin

Mutations in the progranulin (PGRN) gene have been linked to two distinct neurodegenerative diseases, frontotemporal lobar degeneration (FTLD) and neuronal ceroid lipofuscinosis (NCL). Accumulating evidence suggests a critical role of PGRN in lysosomes. However, how PGRN is trafficked to lysosomes is still not clear. Here we report a novel pathway for lysosomal delivery of PGRN. We found that prosaposin (PSAP) interacts with PGRN and facilitates its lysosomal targeting in both biosynthetic and endocytic pathways via the cation-independent mannose 6-phosphate receptor and low density lipoprotein receptor-related protein 1. PSAP deficiency in mice leads to severe PGRN trafficking defects and a drastic increase in serum PGRN levels. We further showed that this PSAP pathway is independent of, but complementary to, the previously identified PGRN lysosomal trafficking mediated by sortilin. Collectively, our results provide new understanding on PGRN trafficking and shed light on the molecular mechanisms behind FTLD and NCL caused by PGRN mutations.