PCDH17 restricts dendritic spine morphogenesis by regulating ROCK2-dependent control of the actin cytoskeleton,modulating emotional behavior

Proper regulation of synapse formation and elimination is critical for establishing mature neuronal circuits and maintaining brain function.Synaptic abnormalities,such as defects in the density and morphology of postsynaptic dendritic spines,underlie the pathology of various neuropsychiatric disorders.Protocadherin 17(PCDH17)is associated with major mood disorders,including bipolar disorder and depression.However,the molecular mechanisms by which PCDH17 regulates spine number,morphology,and behavior remain elusive.In this study,we found that PCDH17 functions at postsynaptic sites,restricting the number and size of dendritic spines in excitatory neurons.Selective overexpression of PCDH17 in the ventral hippocampal CA1 results in spine loss and anxiety-and depression-like behaviors in mice.Mechanistically,PCDH17 interacts with actin-relevant proteins and regulates actin filament(F-actin)organization.Specifically,PCDH17 binds to ROCK2,increasing its expression and subsequently enhancing the activity of downstream targets such as LIMK1 and the phosphorylation of cofilin serine-3(Ser3).Inhibition of ROCK2 activity with belumosudil(KD025)ameliorates the defective F-actin organization and spine structure induced by PCDH17 overexpression,suggesting that ROCK2 mediates the effects of PCDH17 on F-actin content and spine development.Hence,these findings reveal a novel mechanism by which PCDH17 regulates synapse development and behavior,providing pathological insights into the neurobiological basis of mood disorders.

Scinderin promotes glioma cell migration and invasion via remodeling actin cytoskeleton

BACKGROUND Glioma is one of the most common intracranial tumors,characterized by invasive growth and poor prognosis.Actin cytoskeletal rearrangement is an essential event of tumor cell migration.The actin dynamics-related protein scinderin(SCIN)has been reported to be closely related to tumor cell migration and invasion in several cancers.AIM To investigate the role and mechanism of SCIN in glioma.METHODS The expression and clinical significance of SCIN in glioma were analyzed based on public databases.SCIN expression was examined using real-time quantitative polymerase chain reaction and Western blotting.Gene silencing was performed using short hairpin RNA transfection.Cell viability,migration,and invasion were assessed using cell counting kit 8 assay,wound healing,and Matrigel invasion assays,respectively.F-actin cytoskeleton organization was assessed using F-actin staining.RESULTS SCIN expression was significantly elevated in glioma,and high levels of SCIN were associated with advanced tumor grade and wild-type isocitrate dehydrogenase.Furthermore,SCIN-deficient cells exhibited decreased proliferation,migration,and invasion in U87 and U251 cells.Moreover,knockdown of SCIN inhibited the RhoA/focal adhesion kinase(FAK)signaling to promote F-actin depolymerization in U87 and U251 cells.CONCLUSION SCIN modulates the actin cytoskeleton via activating RhoA/FAK signaling,thereby promoting the migration and invasion of glioma cells.This study identified the cancer-promoting effect of SCIN and provided a potential therapeutic target for the treatment of glioma.

Regulation of actin cytoskeleton via photolithographic micropatterning

Actin cytoskeleton plays crucial roles in various cellular functions.Extracellular matrix(ECM)can modulate cell morphology by remodeling the internal cytoskeleton.To define how geometry of ECM regulates the organization of actin cytoskeleton,we plated individual NIH 3T3 cells on micropatterned substrates with distinct shapes and sizes.It was found that the stress fibers could form along the nonadhesive edges of T-shaped pattern,but were absent from the opening edge of V-shaped pattern,indicating that the organization of actin cytoskeleton was dependent on the mechanical environment.Furthermore,a secondary actin ring was observed on 50μm circular pattern while did not appear on 30μm and 40μm pattern,showing a size-dependent organization of actin cytoskeleton.Finally,osteoblasts,MDCK and A549 cells exhibited distinct organization of actin cytoskeleton on T-shaped pattern,suggesting a cell-type specificity in arrangement of actin cytoskeleton.Together,our findings brought novel insight into the organization of actin cytoskeleton on micropatterned environments.

Effects of dexamethasone and HA1077 on actin cytoskeleton and β-catenin in cultured human trabecular meshwork cells

AIM：To investigate the effects of dexamethasone（DEX） and 1-（5-isoquinolinesulfonyl）-homopiperazine（HA1077） on actin cytoskeleton and β-catenin in cultured human trabecular meshwork（HTM） cells.METHODS： The HTM cells were separated from human eyeball and cultured in vitro.They were divided into control group,DEX（1×10^-6mol/L） group,HA1077（3×10^-5mol/L）group,and DEX（1×10^-6mol/L） and HA1077（3×10^-5mol/L）group.Actin cytoskeleton and β-catenin in HTM cells of the four groups were examined by immunofluorescence and Western blot analyses.RESULTS： In DEX group,there were reorganization of actin cytoskeleton and formation of cross linked actin networks（CLANs）,which were partially reversed in DEX and HA1077 group.DEX treatment also induced an increased expression of β-catenin,which was obviously reduced in DEX and HA1077 group.Meanwhile,the cultured HTM cells in HA1077 group had lower expression of β-catenin than that in the control group. CONCLUSION： Our results show that HA1077 can reverse the changes of actin organization and expression of β-catenin induced by DEX in cultured HTM cells,suggesting that HA1077 may play an important role in increasing outflow and reducing intraocular pressure.

Ion Implantation Hampers Pollen Tube Growth and Disrupts Actin Cytoskeleton Organization in Pollen Tubes of Pinus thunbergii

Pollen grains of Pinus thunbergii Parl. （Japanese black pine） were implanted with 30 keV nitrogen ion beams and the effects of nitrogen ion implantation on pollen tube growth in vitro and the organization of actin cytoskeleton in the pollen tube cell were investigated using a confocal laser scanning microscope after fluorescence labeling. Treatment with ion implantation significantly blocked pollen tube growth. Confocal microscopy showed that ion implantation disrupted actin filament cytoskeleton organization in the pollen tube. It was found that there was a distinct correlation between the inhibition of pollen tube growth and the disruption of actin cytoskeleton organization, indicating that an intact actin cytoskeleton is essential for continuous pollen tube elongation in Pinus thunbergii. Although the detailed mechanism for the ion-implantation-induced bioeffect still remains to be elucidated, the present study assumes that the cytoskeleton system in pollen grains may provide a key target in response to ion beam implantation and is involved in mediating certain subsequent cytological changes.

Hsp90 inhibition induces destabilization of actin cytoskeleton in tumor cells:functional significance of Hsp90 interaction with F-actin

Objective:To examine the role of heat shock protein 90(Hsp90) in the maintenance of actin cytoskeleton in human neuroblastoma tumor cells.Methods:Co-precipitation experiments were performed to examine Hsp90 interaction with actin.Hsp90 and actin interactions were evaluated by protein refolding and acto-myosin motility assays.17-(AUylamino)-17- demethoxygeldanamycin(17AAG) induced actin-cytoskeleton re-organization was examined by laser scanning confocal microcopy.Results:It was shown that inhibition of Hsp90 by 17AAC accelerates detergent induced cell lysis of neuroblastoma tumor cells through destabilization of actin cytoskeleton.The in vitro co-precipitation experiments showed that functional but not mutant Hsp90 binds with F-actin.Among biochemical modifications,phopshorylation and oligomerization enhanced Hsp90 binding with F-actin.F-actin binding to Hsp90 interfered with Hsp90 chaperone activity in protein refolding assays,and Hsp90 binding to F-actin interfered with actin motility on myosin coated flow cell.In the combination treatment,17AAG irreversibly augmented the effect of cytochalasin D,an inhibitor of actin polymerization.Conclusions:It can be concluded that Hsp90 binds to F-actin in tumor cells and maintains the cellular integrity. The results display a novel element of Hsp90 inhibition in destabilizing the actin cytoskeleton of tumor cells,therefore suggest that 17AAG combination with cytoskeletal disruptor may be effective in combating cancer.

From filaments to function: The role of the plant actin cytoskeleton in pathogen perception,signaling and immunity

The eukaryotic actin cytoskeleton is required for numerous cellular processes, including cell shape, development and movement, gene expression and signal transduction, and response to biotic and abiotic stress. In recent years,research in both plants and animal systems have described a function for actin as the ideal surveillance platform, linking the function and activity of primary physiological processes to the immune system. In this review, we will highlight recent advances that have defined the regulation and breadth of function of the actin cytoskeleton as a network required for defense signaling following pathogen infection. Coupled with an overview of recent work demonstrating specific targeting of the plant actin cytoskeleton by a diversity of pathogens,including bacteria, fungi and viruses, we will highlight the importance of actin as a key signaling hub in plants, one that mediates surveillance of cellular homeostasis and the activation of specific signaling responses following pathogen perception. B4 ased on the studies highlighted herein, we propose a working model that posits changes in actin filament organization is in and of itself a highly specific signal, which induces, regulates and physically directs stimulus-specific signaling processes, most importantly, those associated with response to pathogens.

Mutual regulation between Hippo signaling and actin cytoskeleton

Hippo signaling plays a crucial role in growth control and tumor suppression by regulating cell proliferation,apoptosis,and differentiation.How Hippo signaling is regulated has been under extensive investigation.Over the past three years,an increasing amount of data have supported a model of actin cytoskeleton blocking Hippo signaling activity to allow nuclear accumulation of a downstream effector,Yki/Yap/Taz.On the other hand,Hippo signaling negatively regulates actin cytoskeleton organization.This review p rovides insight on the mutual regulatory mechanisms between Hippo signaling and actin cytoskeleton for a tight control of cell behaviors during animal development,and points out outstanding questions for further investigations.

The actin cytoskeleton coordinates the signal transduction and antigen processing functions of the B cell antigen receptor

The B cell antigen receptor （BCR） is the sensor on the B cell surface that surveys foreign molecules （antigen） in our bodies and activates B cells to generate antibody responses upon encountering cognate antigen. The binding of antigen to the BCR induces signaling cascades in the cytoplasm, which provides the first signal for B cell activation. Subsequently, BCRs internalize and target bound antigen to endosomes, where antigen is processed into T cell recognizable forms. T helper cells generate the second activation signal upon binding to antigen presented by B cells. The optimal activation of B cells requires both signals, thereby depending on the coordination of BCR signaling and antigen transport functions. Antigen binding to the BCR also induces rapid remodeling of the cortical actin network of B cells. While being initiated and controlled by BCR signaling, recent studies reveal that this actin remodeling is critical for both the signaling and antigen processing functions of the BCR, indicating a role for actin in coordinating these two pathways. Here we will review previous and recent studies on actin reorganization during BCR activation and BCR- mediated antigen processing, and discuss how actin remodeling translates BCR signaling into rapid antigen uptake and processing while providing positive and negative feedback to BCR signaling.

14-3-3 λ protein interacts with ADF1 to regulate actin cytoskeleton dynamics in Arabidopsis

Actin cytoskeleton dynamics is critical for variety of cellular events including cell elongation, division and morphogenesis, and is tightly regulated by numerous groups of actin binding proteins. However it is not well understood how these actin binding proteins are modulated in a physiological condition by their interaction proteins. In this study, we describe that Arabidopsis 14-3-3 λ protein interacted with actin depolymerizing factor 1(ADF1) in plant to regulate F-actin stability and dynamics. Loss of 14-3-3 λin Arabidopsis resulted in longer etiolated hypocotyls in dark and changed actin cytoskeleton architecture in hypocotyl cells. Overexpression of ADF1 repressed 14-3-3 λ mutant hypocotyl elongation and actin dynamic phenotype. In addition, the phosphorylation level of ADF1 was increased and the subcellular localization of ADF1 was altered in 14-3-3 λ mutant. Consistent with these observations, the actin filaments were more stable in 14-3-3 λ mutant. Our results indicate that 14-3-3 λ protein mediates F-actin dynamics possibly through inhibiting ADF1 phosphorylation in vivo.

Formins:Bringing new insights to the organization of actin cytoskeleton

The actin cytoskeleton is an important component of eukaryotic cell cytoskeleton and is temporally and spatially controlled by a series of actin binding proteins (ABPs). Among ABPs, formin family proteins have attracted much attention as they can nucleate unbranched actin filament from the profilin bound actin pool in vivo. In recent years, a number of formin family members from different organisms have been reported, and their characteristics are known more clearly, although some questions are still to be clarified. Here, we summarize the structures, func-tions and nucleation mechanisms of different formin family proteins, intending to compare them and give some new clues to the study of formins.

Dynamic organization of actin cytoskeleton during the polar-ity formation and germination of pollen protoplasts

The formation of the polarity of pollen proto-plast and the dynamics of actin cytoskeleton were observed by non-fixation, Alexa-Phalloidin probing and confocal laser scanning microscopy. Our results showed that the protoplast obtained from stored pollen contained numerous crystalline fusiform bodies to constitute a storage form of actin. When dormant pollen was hydrated, the actin cytoskeleton forms a fine network spreading uniformly in the protoplast. In the process of polarity formation and germination of pollen pro-toplast, actin filaments marshaled slowly to the brim, and then formed multilayer continuous actin filament bundles surrounding the cortical of the protoplast. When the proto-plast was exposed to actin filament-disrupting drugs, such as Latrunculin A and Cytochalasin D, continuously arranged actin bundles were disturbed and in this condition, the pro-toplast could not germinate. But when exposed to actin fila-ment stabiling drug-phalliodin, the dynamics of actin fila-ments in the protoplasts behaved normally and the proto-plasts could germinate normally. These results were also confirmed by the pharmacology experiments on pollen grains. And when Latrunculin A or Cytochalasin D was washed off, the ratio of pollen germination was resumed partly. All the results above show that the dynamic organiza-tion of the actin cytoskeleton are critical in the cell polarity formation and germination of pollen protoplast, and that the reorganization of actin cytoskeleton is mainly due to the re-arrangement of actin filament arrays.

Dynamics and functions of the actin cytoskeleton during the plant cell cycle

In eukaryotic cells, the course of the cell cycle depends on correct cytoskeleton arrangement. The cell cycle consists of several phases, and in each of them the cytoskeleton has a unique structure and set of characteristics. The dynamics of the cytoskeleton together with its binding proteins greatly contribute to progression of the cell cycle. Here, we mainly review recent research on the dynamic distribution of the actin cytoskeleton and actin-binding proteins, and the mechanisms by which they affect the progression of the plant cell cycle.

阿魏酸对兔受损窦房结细胞骨架F-actin、Vinculin的影响

目的观察阿魏酸对模拟缺血再灌注损伤兔窦房结细胞骨架蛋白F-actin和Vinculin的影响,探讨其保护窦房结细胞的机制。方法取新生乳兔窦房结细胞,以缺氧缺糖模拟缺血,以恢复氧和糖的供应模拟再灌注造成窦房结细胞损伤模型。正常对照组与模型组给予等体积培养基,阿魏酸高、中、低剂量组分别给予相应浓度药物(终浓度分别为100μmol/ml、20μmol/ml、10μmol/ml),运用酶标仪、激光共聚焦显微镜观察各组窦房结细胞活性、细胞骨架蛋白F-actin和Vinculin形态的变化。结果模型组活细胞量较正常对照组明显减少(P<0.01);细胞骨架蛋白F-actin和Vinculin裂解明显。阿魏酸高、中、低剂量组活细胞量明显高于模型组(P<0.01),F-actin和Vinculin结构较模型组明显完整,平均荧光强度明显高于模型组(P<0.01)。结论阿魏酸可抑制模拟缺血再灌注引起的窦房结细胞损伤;阿魏酸保护窦房结细胞的机制可能与保护细胞骨架蛋白F-actin和Vinculin从而维持细胞电生理稳定有关。

转移相关分子链Actin-CD44-MMP-2在乳腺癌转移实验中的改变

目的研究乳腺癌转移相关的分子机制及抑制体内外转移的作用和机制。方法选择高、低转移性乳腺癌细胞系BICR-H1和MCF-7,用明胶底物非变性电泳分析法、Western blot和免疫荧光染色等方法,观察肌动蛋白、CD44和基质金属蛋白酶2分子链（ACM）成员分子的定性与定位关系。利用荧光标记肿瘤鸡胚尿囊膜（CAM）模型,血管内注射顺铂或MMP-2 C末端PEX融合蛋白,利用荧光显微镜直接观察鸡胚肺转移抑制情况与癌细胞的ACM水平。结果高转移的BICR-H1细胞ACM分子链呈高表达,分子定位相互关联。低转移性的MCF-7细胞呈低表达或无表达。体外实验中,顺铂和PEX分别抑制了CD44和MMP-2的表达。体内实验中,5~30μg顺铂能够抑制BICR-H1和MCF-7肿瘤的体内生长,呈剂量依赖性。30μg顺铂使乳腺癌BICR-H1细胞体内转移克隆数下降到（8±6）个[对照组为（30±15）个],而同剂量PEX可以完全抑制其体内转移。结论 ACM分子链表达与乳腺癌的转移性密切相关。顺铂和PEX分别通过封闭ACM分子链的环节,使CD44或MMP-2表达抑制,从而抑制乳腺癌细胞的体内外生长和转移。

Actin-binding Rho activating protein is expressed in the central nervous system of normal adult rats

Previous studies show that actin-binding Rho activating protein （Abra） is expressed in cardiomyocytes and vascular smooth muscle cells. In this study, we investigated the expression profile of Abra in the central nervous system of normal adult rats by confocal immunofluorescence. Results showed that Abra immunostaining was located in neuronal nuclei, cytoplasm and processes in the central nervous system, with the strongest staining in the nuclei; in the cerebral cortex, Abra positive neuronal bodies and processes were distributed in six cortical layers including molecular layer, external granular layer, external pyramidal layer, internal granular layer, internal pyramidal layer and polymorphic layer; in the hippocampus, the cell bodies of Abra positive neurons were distributed evenly in pyramidal layer and granular layer, with positive processes in molecular layer and orien layer; in the cerebellar cortex, Abra staining showed the positive neuronal cell bodies in Purkinje cell layer and granular layer and positive processes in molecular layer; in the spinal cord, Abra-immunopositive products covered the whole gray matter and white matter; co-localization studies showed that Abra was co-stained with F-actin in neuronal cytoplasm and processes, but weakly in the nuclei. In addition, in the hippocampus, Abra was co-stained with F-actin only in neuronal processes, but not in the cell body. This study for the first time presents a comprehensive overview of Abra expression in the central nervous system, providing insights for further investigating the role of Abra in the mature central nervous system.

洋葱鳞茎表皮Actin细胞骨架的Rh-Ph荧光和光学显微镜观察

洋葱鳞茎内表皮细胞经Triton X-100处理和多聚甲醛固定之后用Rh-Ph(Rhodamine-Phalloidin)染色,细胞质内可见较丰富的、直径为100—300nm的F-actin束。较粗的F-actin束沿细胞的长轴平行排列,并纵裂成较细的“分枝”,纵裂成的分枝又纵裂成更细的“分枝”。各种大小的F-actin束相互交织在一起构成一个三维的纤丝网络,并且与细胞膜、细胞核和其它细胞器相连。经同样方法处理和固定的细胞用考马斯亮兰R_(250)(Coomassie brilliant blue R_(250))染色之后,细胞质内可见直径为200—300nm的纤丝,形态特征和排列方式和上述在荧光显微镜下看到的F-actin束相同。本研究结果表明洋葱鳞茎内表皮的细胞骨架包含较丰富的F-actin系统;Pena的考马斯亮兰染色法(1980)所显示的结构主要代表F-actin束。

雌激素β受体对小鼠海马actin聚合调节蛋白表达的影响及其机制

目的初步探讨雌激素β受体(estrogen receptor beta,ERβ)在小鼠海马不同发育时期的表达以及ERβ活性改变对actin细胞骨架聚合调节蛋白表达的影响及其机制。方法 C57BL/6小鼠按性别和出生后时间[出生后0(P0)、7(P7)、14(P14)、28(P28)、56 d(P56)]分为10组,用免疫组化和Western blot检测小鼠海马中ERβ的表达变化。另取动情间期成年雌性C57BL/6小鼠用随机数字表法分为5组:对照组和腹腔注射ERβ活性抑制剂PHTPP(100μg/kg)1、3、5、7 d组。再取同种小鼠用随机数字表法分为5组:假手术对照组,卵巢切除(ovariectomy,OVX)组,OVX 1周后再皮下注射ERβ活性激动剂DPN 1.25、2.5、5.0 mg/kg组,均连续注射1周。用免疫组织化学方法检测海马类固醇受体辅助活化因子-1(steroid receptor coactivator-1,SRC-1)的表达,用Western blot检测海马Rictor、磷酸化蛋白激酶B(phospho-protein kinase B,p-Akt)、Profilin-1、磷酸化cofilin(phospho-cofilin ser3,p-cofilin)和SRC-1的蛋白水平表达变化。结果免疫组化和Western blot检测发现,ERβ在雌、雄小鼠海马P0组表达较高,P7组和P14组表达较P0组降低(P<0.05),而P28组和P56组ERβ表达较P7组和P14组升高(P<0.01)。用PHTPP抑制ERβ活性导致Rictor、p-Akt、Profilin-1、p-cofilin和SRC-1的表达下降(P<0.05),而OVX导致上述分子表达下降可被ERβ活性激动剂DPN逆转(P<0.05)。结论从出生到成年小鼠海马内ERβ的表达呈U型变化。调节ERβ活性可诱导actin细胞骨架聚合调节蛋白及SRC-1的表达发生改变,提示ERβ可能通过SRC-1/Rictor/p-Akt途径对actin细胞骨架聚合状态进行调节并最终介导雌激素(estrogens,E2)对学习记忆的调节。

Actin骨架偶联IRAK-NF-κB信号通路参与细菌脂蛋白诱导的交叉耐受

目的:采用人单核细胞株(THP-1),建立小剂量BLP诱导THP-1细胞对BLP耐受的细胞模型,观察BLP诱导THP-1细胞对BLP耐受及对LPS交叉耐受时细胞actin骨架的变化情况,并探讨细胞actin骨架在BLP耐受及交叉耐受形成中的作用。方法:采用人单核细胞株THP-1,建立小剂量BLP预处理诱导的BLP耐受细胞模型;采用ELISA法测定炎症因子TNF-α、IL-1β及IL-6浓度;采用FITC标记的鬼笔环肽进行actin骨架染色;采用EMSA法检测NF-κB转录活性。结果:大剂量BLP(100μg/L)及大剂量LPS(100μg/L)孵育6h可诱导THP-1细胞的炎症反应激活,TNF-α、IL-1β及IL-6的释放显著增加,白细胞介素-1受体相关激酶-1(IRAK-1)活性显著增强,NF-κB转录活性明显上调,细胞actin骨架收缩成团块状,细胞形态改变并形成伪足;而用小剂量BLP(10μg/L)预处理12h后,THP-1细胞对大剂量BLP(100μg/L)及大剂量LPS(100μg/L)孵育6h的耐受性均明显增强,炎症因子(TNF-α、IL-1β及IL-6的释放明显减少,IRAK-1激酶活性被显著抑制,NF-κB转录活性明显降低,细胞伪足形成明显减少且形态明显改善,但仍有肌动蛋白聚集呈"团块"样;此外,actin骨架聚集抑制剂鬼笔环肽可取消由小剂量BLP诱导的耐受及交叉耐受,TNF-α、IL-1β、IL-6释放明显升高,IRAK-1激酶活性明显提高,NF-κB转录活性明显上调。结论:细胞骨架actin参与THP-1细胞BLP耐受及BLP交叉耐受的形成,其机制与actin骨架偶联的IRAK-NF-κB信号通路有关。