E and ID proteins regulate cell chirality and left–right asymmetric development in Drosophila

How left–right (LR) asymmetric forms in the animal body is a fundamental problem in Developmental Biology. Although the mechanisms for LR asymmetry are well studied in some species, they are still poorly understood in invertebrates. We previously showed that the intrinsic LR asymmetry of cells (designated as cell chirality) drives LR asymmetric development in the Drosophila embryonic hindgut, although the machinery of the cell chirality formation remains elusive. Here, we found that the Drosophila homologue of the Id gene, extra macrochaetae (emc), is required for the normal LR asymmetric morphogenesis of this organ. Id proteins, including Emc, are known to interact with and inhibit E‐box‐binding proteins (E proteins), such as Drosophila Daughterless (Da). We found that the suppression of da by wild‐type emc was essential for cell chirality formation and for normal LR asymmetric development of the embryonic hindgut. Myosin ID (MyoID), which encodes the Drosophila Myosin ID protein, is known to regulate cell chirality. We further showed that Emc‐Da regulates cell chirality formation, in which Emc functions upstream of or parallel to MyoID. Abnormal Id‐E protein regulation is involved in various human diseases. Our results suggest that defects in cell shape may contribute to the pathogenesis of such diseases.     

SDF‐1α stiffens myeloma bone marrow mesenchymal stromal cells through the activation of RhoA‐ROCK‐Myosin II

Multiple myeloma (MM) is a B lymphocyte malignancy that remains incurable despite extensive research efforts. This is due, in part, to frequent disease recurrences associated with the persistence of myeloma cancer stem cells (mCSCs). Bone marrow mesenchymal stromal cells (BMSCs) play critical roles in supporting mCSCs through genetic or biochemical alterations. Previously, we identified mechanical distinctions between BMSCs isolated from MM patients (mBMSCs) and those present in the BM of healthy individuals (nBMSCs). These properties of mBMSC contributed to their ability to preferentially support mCSCs. To further illustrate mechanisms underlying the differences between mBMSCs and nBMSCs, here we report that (i) mBMSCs express an abnormal, constitutively high level of phosphorylated Myosin II, which leads to stiffer membrane mechanics, (ii) mBMSCs are more sensitive to SDF‐1α‐induced activation of MYL2 through the G_(i./o)‐PI3K‐RhoA‐ROCK‐Myosin II signaling pathway, affecting Young's modulus in BMSCs and (iii) activated Myosin II confers increased cell contractile potential, leading to enhanced collagen matrix remodeling and promoting the cell–cell interaction between mCSCs and mBMSCs. Together, our findings suggest that interfering with SDF‐1α signaling may serve as a new therapeutic approach for eliminating mCSCs by disrupting their interaction with mBMSCs.     

肌球蛋白轻链磷酸化与心肌损伤的实验研究

应用水平平板等电聚焦(电压2000V,时间2.5h、pH 4～6)、银染和凝胶光密度扫描相结合的一种新方法,研究去甲肾上腺素性心肌损伤兔心肌肌球蛋白轻链磷酸化(P-MLC/MLC×100%)的改变及α、β受体阻滞剂对该改变的影响。结果表明,去甲肾上腺素(NE,2mg/kg)显著降低心肌的P-MLC/MLC(P-MLC/MLC为35.40±5.37%;对照组为61.07±6.97%,P<0.01),酚妥拉明(10mg/只)可保护心肌P-MLC 66.43±8.43%,而普萘洛尔则无此作用(P-MLC/MLC为36.54±4.05%)。     

肌球蛋白重链基因Arg663Cys和Arg663His突变基因型与家族性肥厚型心肌病表型关系研究

目的：研究中国人家族性肥厚型心肌病相关致病基因，揭示致病基因型与临床表型的关系。方法；在60例门诊肥厚型心肌病患者及60例正常对照中进行β－肌球蛋白重链（β－MHC）基因突变扫描，聚合酶链反应扩增其功能区外显子基因片断，测序检测突变，对阳性结果者进行家系调查，限制性片断长度多态性分析其他家系成员。结果：在一患者及其家系中发现位于β－MHC基因第18号外显子的663密码子位置发生C→T转换，使精氨酸变为半胱氨酸，该突变以前未见报道，在另两个患者及其家系中同样在663密码子位置发生C→A转换，使精氨酸变为组氨酸，3个家系基因型类似但临床表型不同。前者表现为进行性心力衰竭，心房颤动，外显率100％，而后者临床表现则相对轻微，呈不完全外显，另外57例患者和60例正常对照未发现异常。结论：β－MHC同一位置基因突变表现为不同的临床表型，提示即使是在同一种族（中国人群）中肥厚型心肌病亦存在异质性遗传特点。     

Increased cardiac myosin ATPase activity as a biochemical adaptation to running training: enhanced response to catecholamines and a role for myosin phosphorylation

The effects were studied of prior running training on protein phosphorylation and adenosine triphosphatase (ATPase) activities of natural actomyosin isolated from perfused rat hearts. Myosin Ca²⁺-ATPase activities were significantly higher in running-trained hearts than in controls, whereas the Ca²⁺-stimulated, Mg²⁺-dependent ATPase activities of natural actomyosin were not changed. After treatment of isolated perfused hearts with the β-agonist isoproterenol, both troponin-I and myosin P light chains became phosphorylated. Troponin-I phosphorylation (1 mol/mol) was the same in both sets of hearts and was accompanied by similar changes in cardiac cyclic AMP contents. The V_max values for myosin Ca²⁺-ATPase activity were increased after isoproterenol treatment in all the perfused hearts, but to a significantly greater extent in the hearts of running trained animals; this was correlated with enhancement of both the rate and extent of myosin P light chain phosphorylation. Enhanced Ca²⁺-dependent myosin P light chain phosphorylation, further enhanced by β-adrenergic stimulation, represents, at the molecular level, a biochemical response to running training.     

The effect of certain high cardiac output states on dog heart myosin ATPase

This work was done to evaluate the response of cardiac myosin ATPase in the compensated heart subjected to the increased volume work of a high cardiac-output state.Dogs with bilateral femoral arteriovenous fistulas were studied either 14 days (acute arteriovenous fistulas) or a mean of 230 days (chronic arteriovenous fistulas) after construction of the fistulas. Dogs with anemia secondary to repeated bleeding (anemic) were studied 14 days after a high output state was first documented.Calcium-activated myosin adenosine-triphosphatase (ATPase) activity was significantly elevated for the anemic and acute arteriovenous fistula dogs, but the elevations were not significant for myosin from the chronic arteriovenous fistula dogs. In the presence of K⁺ and EDTA, the cardiac myosin ATPase activity was generally elevated for the anemic, less so for the acute arteriovenous fistula and was normal for the chronic arteriovenous fistula.The Ca²⁺ uptake (in the presence of oxalate) by the cardiac sarcoplasmic reticulum was significantly less than normal for all three groups.     

肌球蛋白在生物力学效应中的调控作用

细胞骨架是细胞内机械力传递链的一个组分,肌球蛋白作为细胞骨架的主要组成蛋白,对细胞受到外界力作用时产生的效应具有一定的调控作用,当细胞内的肌球蛋白的表达、结构以及活性发生改变时,细胞的力学效能也会发生相应的改变,从而影响细胞的功能以及组织结构的改变。肌球蛋白轻链的磷酸化、重链各亚型间的转化以及Rho GTP酶信号通路在对细胞生物力学效应的调控中起着一定的作用。