Plakins in development and disease

Plakins are large multi-domain molecules that have various functions to link cytoskeletal elements together and to connect them to junctional complexes. Plakins were first identified in epithelial cells where they were found to connect the intermediate filaments to desmosomes and hemidesmosomes [Ruhrberg, C., and Watt, F.M. (1997). The plakin family: versatile organizers of cytoskeletal architecture. Curr Opin Genet Dev 7, 392-397.]. They were subsequently found to be important for the integrity of muscle cells. Most recently, they have been found in the nervous system, where their functions appear to be more complex, including cross-linking of microtubules (MTs) and actin filaments [Leung, C.L., Zheng, M., Prater, S.M., and Liem, R.K. (2001). The BPAG1 locus: Alternative splicing produces multiple isoforms with distinct cytoskeletal linker domains, including predominant isoforms in neurons and muscles. J Cell Biol 154, 691-697., Leung, C.L., Sun, D., Zheng, M., Knowles, D.R., and Liem, R.K. (1999). Microtubule actin cross-linking factor (MACF): a hybrid of dystonin and dystrophin that can interact with the actin and microtubule cytoskeletons. J Cell Biol 147, 1275-1286.]. These plakins have also indicated their relationship to the spectrin superfamily of proteins and the plakins appear to be evolutionarily related to the spectrins, but have diverged to perform different specialized functions. In invertebrates, a single plakin is present in both Drosophila melanogaster and Caenorhabditis elegans, which resemble the more complex plakins found in mammals [Roper, K., Gregory, S.L., and Brown, N.H. (2002). The 'spectraplakins': cytoskeletal giants with characteristics of both spectrin and plakin families. J Cell Sci 115, 4215-4225.]. In contrast, there are seven plakins found in mammals and most of them have alternatively spliced forms leading to a very complex group of proteins with potential tissue specific functions [Jefferson, J.J., Leung, C.L., and Liem, R.K. (2004). Plakins: goliaths that link cell junctions and the cytoskeleton. Nat Rev Mol Cell Biol 5, 542-553.]. In this review, we will first describe the plakins, desmoplakin, plectin, envoplakin and periplakin and then describe two other mammalian plakins, Bullous pemphigoid antigen 1 (BPAG1) and microtubule actin cross-linking factor 1 (MACF1), that are expressed in multiple isoforms in different tissues. We will also describe the relationship of these two proteins to the invertebrate plakins, shortstop (shot) in Drosophila and VAB-10 in C. elegans. Finally, we will describe an unusual mammalian plakin, called epiplakin.     

The citrus fruit proteome: insights into citrus fruit metabolism

Fruit development and ripening are key processes in the production of the phytonutrients that are essential for a balanced diet and for disease prevention. The pathways involved in these processes are unique to plants and vary between species. Climacteric fruit ripening, especially in tomato, has been extensively studied; yet, ripening of non-climacteric fruit is poorly understood. Although the different species share common pathways; developmental programs, physiological, anatomical, biochemical composition and structural differences must contribute to the operation of unique pathways, genes and proteins. Citrus has a non-climacteric fruit ripening behavior and has a unique anatomical fruit structure. For the last few years a citrus genome-wide ESTs project has been initiated and consists of 222,911 clones corresponding to 19,854 contigs and 37,138 singletons. Taking advantage of the citrus database we analyzed the citrus proteome. Using LC-MS/MS we analyzed soluble and enriched membrane fractions of mature citrus fruit to identify the proteome of fruit juice cells. We have identified ca. 1,400 proteins from these fractions by searching NCBI-nr (green plants) and citrus ESTs databases, classified these proteins according to their putative function and assigned function according to known biosynthetic pathways.     

垂体后叶素和加压素对离体心肌的直接作用

本实验采用大鼠离体右心房和右心室肌条模型,观察了垂体后叶素和加压素对右心房和右心室肌的直接作用。结果表明:垂体后叶素对右心房的自主性收缩频率和幅度及右心室肌的收缩幅度均有剂量依赖性抑制作用;加压素对右心房和右心室肌收缩幅度也有剂量依赖性抑制作用,但对右心房自主节律无影响;催产素对右心房的收缩频率和幅度则均无影响。加压素V_1、V_2受体拮抗剂d(CH_2)_5Tyr(Me)AVP和d(CH_2)_5(D-Ile~2,Ile~4,Ala(NH_2)~9)AVP对垂体后叶素的负性变力作用具有不同程度的阻断作用,但对垂体后叶素的负性变时作用无阻断作用。以上结果提示,垂体后叶素的负性变力作用主要是由加压素产生的,加压素对心肌有直接的负性变力作用;垂体后叶素的负性变时作用可能是非加压素和催产素成分的作用结果。     

A-kinase anchoring protein-Lbc promotes pro-fibrotic signaling in cardiac fibroblasts

In response to stress or injury the heart undergoes an adverse remodeling process associated with cardiomyocyte hypertrophy and fibrosis. Transformation of cardiac fibroblasts to myofibroblasts is a crucial event initiating the fibrotic process. Cardiac myofibroblasts invade the myocardium and secrete excess amounts of extracellular matrix proteins, which cause myocardial stiffening, cardiac dysfunctions and progression to heart failure. While several studies indicate that the small GTPase RhoA can promote profibrotic responses, the exchange factors that modulate its activity in cardiac fibroblasts are yet to be identified. In the present study, we show that AKAP-Lbc, an A-kinase anchoring protein (AKAP) with an intrinsic Rho-specific guanine nucleotide exchange factor (GEF) activity, is critical for activating RhoA and transducing profibrotic signals downstream of type I angiotensin II receptors (AT₁Rs) in cardiac fibroblasts. In particular, our results indicate that suppression of AKAP-Lbc expression by infecting adult rat ventricular fibroblasts with lentiviruses encoding AKAP-Lbc specific short hairpin (sh) RNAs strongly reduces the ability of angiotensin II to promote RhoA activation, differentiation of cardiac fibroblasts to myofibroblasts, collagen deposition as well as myofibroblast migration. Interestingly, AT₁Rs promote AKAP-Lbc activation via a pathway that requires the α subunit of the heterotrimeric G protein G12. These findings identify AKAP-Lbc as a key Rho-guanine nucleotide exchange factor modulating profibrotic responses in cardiac fibroblasts.     

A unique case of a discontinuous duplication 3q26.1-3q28 resulting from a segregation error of a maternal complex chromosomal rearrangement involving an insertion and an inversion

Until now, few cases of partial trisomy of 3q due to segregation error of parental balanced translocation and segregation of a duplicated deficient product resulting from parental pericentric inversion have been reported so far. Only five cases of chromosomal insertion malsegregation involving 3q region are available yet, thus making it relatively rare. In this case report, we are presenting a unique case of discontinuous partial trisomy of 3q26.1-q28 region which resulted from a segregation error of two insertions involving 3q26.1 to 3q27.3 and 3q28 regions with ~ 21 Mb and ~ 2 Mb sizes, respectively. The maternally inherited insertion was cytogenetically characterized as der(8)(8pter → 8p22::3q26 → 3q27.3::3q28 → 3q28::8p22 → 8qter) and the patient's major clinical features involved Dandy Walker malformation, sub-aortic ventricular septal defect, upslanting palpebral fissures, clinodactyly, hirsutism, and prominent forehead. Besides, a review of the literature involving cases with similar chromosomal imbalances and cases with “3q-duplication syndrome” is also provided.     

Generation of mouse conditional and null alleles of the type III sodium‐dependent phosphate cotransporter PiT‐1

Accelerated vascular calcification occurs in several human diseases including diabetes and chronic kidney disease (CKD). In patients with CKD, vascular calcification is highly correlated with elevated serum phosphate levels. In vitro, elevated concentrations of phosphate induced vascular smooth muscle cell matrix mineralization, and the inorganic phosphate transporter‐1 (PiT‐1), was shown to be required. To determine the in vivo role of PiT‐1, mouse conditional and null alleles were generated. Here we show that the conditional allele, PiT‐1^flox, which has loxP sites flanking exons 3 and 4, is homozygous viable. Cre‐mediated recombination resulted in a null allele that is homozygous lethal. Examination of early embryonic development revealed that the PiT‐1^{Δe3,4/Δe3,4} embryos displayed anemia, a defect in yolk sac vasculature, and arrested growth. Thus, conditional and null PiT‐1 mouse alleles have been successfully generated and PiT‐1 has a necessary, nonredundant role in embryonic development. genesis 47:858–863, 2009. © 2009 Wiley‐Liss, Inc.     

高血压前期患者颈动脉血管弹性超声参数与左室舒张功能的关系研究

摘要 目的：研究高血压前期患者颈动脉血管弹性超声参数与左室舒张功能的关系。方法：选取2019年12月-2020年12月因血压异常于河北北方学院附属第一医院接受诊断与治疗的161例患者,根据血压水平分为高血压前期组（82例）与高血压组（79例）;另选取同期于我院体检的80例健康志愿者作为对照组。收集三组临床资料,检测生化指标与血压;通过超声诊断仪中超声射频信号血管内中膜定量分析（QIMT）与动脉僵硬度定量分析（QAS）软件测量颈动脉血管弹性超声参数[颈动脉内中膜厚度（IMT）、顺应性系数（CC）、扩张性系数（DC）、血管弹性指数（α、β）、脉搏波传导速度（PWV）];超声心动图检查左室功能指标[左室射血分数（LVEF）、左室质量指数（LVMI）、舒张早期血流速度峰值（E）/舒张晚期血流速度峰值（A）、等容舒张时间（IVRT）、舒张期减速时间（DT）];采用Pearson相关性法分析颈动脉血管弹性超声参数与心室指标的相关性。结果：三组收缩压与舒张压水平存在统计学意义（P＜0.05）。高血压前期组与高血压组IMT、α、β、PWV高于对照组,DC、CC低于对照组（P＜0.05）,且高血压前期组IMT、α、β、PWV低于高血压组,DC、CC高于高血压组（P＜0.05）。高血压前期与高血压组E/A低于对照组,IVRT、DT高于对照组（P＜0.05）,且高血压前期组E/A高于高血压组,IVRT、DT低于高血压组（P＜0.05）。经Peason相关性分析显示,IMT、α、β、PWV与E/A呈负相关,与IVRT、DT呈正相关（P＜0.05）;DC、CC与E/A呈正相关,与IVRT、DT呈负相关（P＜0.05）。结论：高血压前期患者颈动脉血管弹性功能下降,且伴有左室舒张功能受损,颈动脉血管弹性超声参数与左室舒张功能密切相关。     

心肌带收缩率与急性心肌梗死患者左心室收缩功能关系

目的:急性前壁心肌梗死明显影响室间隔收缩率和左心室射血分数(left ventricular ejection fraction LVEF)。本文旨在探讨心肌带降段及升段收缩率与急性前壁心肌梗死患者LVEF的相关性。方法:收集2015年4月-2017年2月在心内科住院的急性前壁心肌梗死患者36例,正常对照组患者39例。所有患者取左心室长轴M型超声心动图,测量室间隔收缩率、升段收缩率及降段收缩率。心肌梗死左心室射血分数采用双平面Simpson's法计算。结果:与正常对照组相比,心肌梗死组患者舒张末期心肌带升段厚度没有统计学差异(P=0.69),收缩末期升段厚度(P=0.014)更薄、升段收缩率(P0.01)明显降低;心肌梗死组舒张末期降段厚度(P0.01)更薄、收缩末期降段厚度(P0.01)更薄、降段收缩率(P0.01)明显降低;心肌梗死组左心室射血分数与降段收缩率(r~2=0.13,P=0.026)、室间隔增厚率(r~2=0.19,P0.01)呈正相关,与升段收缩率没有相关性(P0.05)。正常对照组左心室射血分数与室间隔增厚率、降段增厚率及升段增厚率无相关性。经过相关分析,筛选出与心肌梗死LVEF的相关因素,进一步经逐步回归分析,得多元线性回归方程为LVEF=48.206+18.914*LVDD(cm)-25.414*LVSD(cm)。结论:急性前壁心肌梗死室间隔降段收缩率明显受损,与左心室射血分数降低有关。多元线性回归方程可估算前壁心肌梗死LVEF。