大肠癌组织中talin mRNA的表达及意义

目的探讨踝蛋白（talin）mRNA在大肠癌组织中的表达变化及其在大肠癌发生、发展中的作用。方法采用荧光定量逆转录PCR（FQ-RT-PCR）方法检测41例大肠癌及癌旁正常组织中talin mRNA的表达。结果talin mRNA在大肠癌组织中的表达量为126535copy／μg RNA，而在癌旁正常组织中为22689376copy／μg RNA，两者相比，P〈0．01；有淋巴结转移的大肠癌较无转移者talin mRNA表达低，P〈0．01；癌组织浸润越深，talin mRNA表达越低，P〈0．01。结论talin mRNA在大肠癌中表达降低；talin与大肠癌的浸润、转移有关，可作为大肠癌发生、发展的预测指标之一。     

Myr-RKEFAK肽选择性调控血小板外向内信号转导相关功能

目的:研究踝蛋白杆部整合素结合位点2与整合素β3相互作用对于血小板信号转导的影响。方法:设计合成模拟整合素β3胞浆近膜端α螺旋上6个氨基酸序列(R724KEFAK729)的寡肽,并通过十四烷酰化修饰以使其具有穿细胞膜性(myr-RKEFAK肽)。观察myr-RKEFAK肽对经典血小板外向内信号转导事件(固相纤维蛋白原上的稳定黏附和伸展、二相聚集、纤维蛋白凝块回缩),以及内向外信号转导事件(一相聚集、游离纤维蛋白原的结合)的影响。结果:myr-RKEFAK肽可以浓度依赖性地抑制血小板固相化纤维蛋白原上稳定黏附和伸展、二相聚集以及纤维蛋白凝块回缩等外向内信号转导功能;但不影响游离纤维蛋白原结合和一相聚集等内向外信号转导功能。结论:穿膜肽myr-RKEFAK对血小板的外向内信号转导相应功能产生抑制,但不影响血小板内向外信号转导相关功能。     

P-selectin-mediated platelet adhesion promotes tumor growth

Blood platelets foster carcinogenesis. We found that platelets are accumulated in human tumors. P-selectin deficiency and soluble P-selectin abolish platelet deposition within tumors, decreasing secretion of vascular endothelial growth factor and angiogenesis, thereby suppressing tumor growth. Binding of the P-selectin cytoplasmic tail to talin1 triggers the talin1 N-terminal head to interact with the β3 cytoplasmic tail. This activates αIIbβ3 and recruits platelets into tumors. Platelet infiltration into solid tumors occurs through a P-selectin-dependent mechanism.     

机械力对人骶韧带成纤维细胞形态及合成功能的调节

目的探究机械力对非盆底器官脱垂(POP)患者骶韧带成纤维细胞形态及整合素β1(integrinβ1)、踝蛋白(talin)、细胞外基质(ECM)mRNA表达的调节。方法选取2009年10月至2010年9月河北医科大学二院非POP患者15例,进行骶韧带成纤维细胞的原代培养,并鉴定。取3～4代的骶韧带成纤维细胞加载力,加载时间分为0(对照组)、4、12、24h,提取RNA,荧光实时定量PCR测定机械力对integrinβ1、talin、Ⅰ、Ⅲ型胶原、基质金属蛋白酶-1(MMP-1)mRNA表达量的影响。结果应力刺激下,细胞的形态和伸展方向发生改变。integrinβ1mR-NA4、15、24h表达量(18.822±5.545,32.527±2.212,40.357±5.140)较0h(1.003±0.064)升高,差异有统计学意义(P=0.000)。talin mRNA4、15、24h表达量(109.804±34.875,106.574±35.477,863.206±144.361)较0h(1.009±0.468)升高,差异有统计学意义(P=0.000)。Ⅰ型胶原mRNA4、15h表达量(0.753±0.192,0.701±0.023)较0h(1.000±0.129)下降,差异有统计学意义(P=0.008),但在24h后回升至1.113±0.049。Ⅲ型胶原mRNA4、15、24h表达量(4.792±1.612,6.146±1.169,5.021±0.940)较0h(1.001±0.249)升高,差异有统计学意义(P=0.002)。MMP-1mRNA4、15、24h表达量(6.233±1.690,23.173±9.251,20.133±7.100)较0h(1.000±0.100)升高,差异有统计学意义(P=0.005)。结论细胞的形态、伸展方向和合成功能受机械力的调节,基质重塑可能是细胞对机械力的适应性改变。     

Identification of indothiazinone as a natural antiplatelet agent

Cardiovascular disease, which is caused by unregulated platelet aggregation, is one of the main causes of deaths worldwide. Many studies have focused on natural products with antiplatelet effects as a safe alternative therapy to prevent the disease. In this context, an in‐house chemical library was screened to find natural products capable of inhibiting the interaction between platelet integrin αIIbβ3 and fibrinogen, which is an essential step in platelet aggregation. On the basis of the screening results, indothiazinone, an alkaloid found in microbial cultures, was identified as a potential antiplatelet agent. Specifically, indothiazinone treatment significantly inhibited the binding of fibrinogen to Chinese hamster ovary cells expressing integrin αIIbβ3. It also restricted thrombin‐ and adenosine diphosphate‐dependent spreading of human platelets on a fibrinogen matrix. More importantly, surface plasmon resonance and molecular dynamics studies suggested that indothiazinone suppressed talin‐induced activation of integrin αIIbβ3 presumably by inhibiting talin–integrin interaction. In conclusion, these results suggest that indothiazinone can be used as a lead compound for the development of antiplatelet drugs with a novel mode of action.     

GATA-1, G208S macrothrombocytes are deficient in talin: Immunofluorescence studies

Previous investigations from our laboratory identified the ultrastructural pathology and cytochemistry of macrothrombocytes (MTC) from patients with the X-linked, G208S varient of the GATA-1 mutation.A subsequent biochemical study of the MTC cytoskeletal proteins using polyacrylamide gel electrophoresis and western blot analysis revealed the MTC were deficient in the high-molecular weight, actin binding protein, talin. The present study has used immunofluorescent techniques to further characterize the talin deficiency. Results confirm that the GATA-1, G208S MTC are deficient in talin, and what little is present relocates to the undersurface of the plasma membrane following activations where it associates with adhesion plaques.     

Integrins in platelet activation

Summary.  Heterodimeric receptors of the β1 and β3 integrin families mediate platelet adhesion and aggregation in hemostasis and thrombosis. In resting platelets, integrins are expressed in a low-affinity state but they shift to a high-affinity state and efficiently bind their ligands in response to cellular activation. This review summarizes recent advances in understanding the functional regulation and (patho-) physiological significance of individual platelet integrins with a special focus on studies in genetically modified mice. It is now recognized that β1 and β3 integrins have partially redundant roles in the adhesion process and that their activation is regulated by similar mechanisms, involving Ca²⁺-dependent and -independent signaling events and essential functions of talin-1 and kindlin-3 in the terminal activation step.     

Stalin's last years: delusions or dementia?

The sheer scale of Stalin's achievements and institutionalized terror has prompted some authors to label him as a paranoid megalomaniac. Whatever the merits of this diagnosis, his undeniable accomplishments and the rationality of many of his actions cannot be explained by the workings of a disturbed mind. In his last years, however, his life-long suspiciousness became florid paranoia. He eschewed medical advice, listening to a veterinarian and treating his hypertension with iodine drops. Stalin feared his own shadow and trusted no-one, even himself. He increasingly withdrew from official functions and he muttered menacingly to his close associates that it was time for another purge. Stalin suffered at least one stroke prior to his fatal intracerebral haemorrhage in 1953. Given his untreated hypertension and the autopsy report, it is probable that he had a number of lacunar strokes. These tend to predominate in the fronto-basal areas, and disconnect the circuits that underpin cognition and behaviour. The most plausible explanation of Stalin's late behaviour is the dimming of a superior intellect and the unleashing of a paranoid personality by a multi-infarct state.     

Integrin activation by talin

The development and integrity of the cardiovascular system depends on integrins, a family of adhesion receptors, vitally important for homeostasis of animal species from fruit fly to man. Integrins are critical players in cell migration, cell adhesion, cell cycle progression, differentiation, and apoptosis. Consequently, integrins have a major impact on the patterning and functions of the blood and cardiovascular system. Integrins undergo conformational changes, which alter their affinity for ligands through a process operationally defined as integrin activation. Integrin activation is important for platelet aggregation, leukocyte extravasation, and cell adhesion and migration, thus influencing such processes as hemostasis, inflammation and angiogenesis. Recently, a series of studies have begun to define the mechanism of integrin activation by demonstrating that binding of a cytoskeletal protein, talin, to integrin beta subunit cytoplasmic tail is a last common step in integrin activation. These findings indicate that talin is likely to be at the center of converging signaling pathways regulating integrin activation.