Phosphorylation of DARPP-32 by Cdk5 modulates dopamine signalling in neurons

The physiological state of the cell is controlled by signal transduction mechanisms which regulate the balance between protein kinase and protein phosphatase activities. Here we report that a single protein can, depending on which particular amino-acid residue is phosphorylated, function either as a kinase or phosphatase inhibitor. DARPP-32 (dopamine and cyclic AMP-regulated phospho-protein, relative molecular mass 32,000) is converted into an inhibitor of protein phosphatase 1 when it is phosphorylated by protein kinase A (PKA) at threonine 34. We find that DARPP-32 is converted into an inhibitor of PKA when phosphorylated at threonine 75 by cyclin-dependent kinase 5 (Cdk5). Cdk5 phosphorylates DARPP-32 in vitro and in intact brain cells. Phospho-Thr 75 DARPP-32 inhibits PKA in vitro by a competitive mechanism. Decreasing phospho-Thr 75 DARPP-32 in striatal slices, either by a Cdk5-specific inhibitor or by using genetically altered mice, results in increased dopamine-induced phosphorylation of PKA substrates and augmented peak voltage-gated calcium currents. Thus DARPP-32 is a bifunctional signal transduction molecule which, by distinct mechanisms, controls a serine/threonine kinase and a serine/threonine phosphatase.     

随机扰动下DNA三核苷酸重复序列的弯曲和柔性

利用统计力学模型讨论了与人类遗传病有关的DNA三核苷酸重复序列的弯曲和柔性,提出随机成动模型来近似表示DNA序列和蛋白质的相互作用,发现弯曲很小的三核苷重复序列在有随机扰动的情况下,可以出现大角度的弯曲,且随扰动强度的加大出现大角度弯曲的概率增加,求出了十二种三核苷重复序列的柔性及其长度依赖,发现当序列长度大于150 bp时,柔性的变化开始显,CTG和CGG具有最大的柔性,研究了柔性在有随机扰动时下的变化,发现在序列上不同位置施加扰动,柔性的变化程度不同,对于600bp长的序列,在390bp处的柔性变化程度最大。     

Mutations in the chromatin modifier gene KANSL1 cause the 17q21.31 microdeletion syndrome

We show that haploinsufficiency of KANSL1 is sufficient to cause the 17q21.31 microdeletion syndrome, a multisystem disorder characterized by intellectual disability, hypotonia and distinctive facial features. The KANSL1 protein is an evolutionarily conserved regulator of the chromatin modifier KAT8, which influences gene expression through histone H4 lysine 16 (H4K16) acetylation. RNA sequencing studies in cell lines derived from affected individuals and the presence of learning deficits in Drosophila melanogaster mutants suggest a role for KANSL1 in neuronal processes.     

Aryl-hydrocarbon receptor-dependent alteration of FAK/RhoA in the inhibition of HUVEC motility by 3-methylcholanthrene

We previously demonstrated the antiproliferative and antiangiogenic effects of 3-methylcholanthrene (3MC), an aryl-hydrocarbon receptor (AhR) agonist, in human umbilical vascular endothelial cells (HUVECs). Herein, we unraveled its molecular mechanisms in inhibiting HUVEC motility. 3MC down-regulated FAK, but up-regulated RhoA, which was rescued by AhR knockdown. It led us to identify novel AhR binding sites in the FAK/RhoA promoters. Additionally, 3MC increased RhoA activity via suppression of a negative feedback pathway of FAK/p190RhoGAP. With an increase in membrane-bound RhoA, subsequent stress fiber and focal adhesion complex formation was observed in 3MC-treated cells, and this was reversed by a RhoA inhibitor and AhR antagonists. Notably, these compounds significantly reversed 3MC-mediated anti-migration in a transwell assay. The in vitro findings were further confirmed using an animal model of Matrigel formation in Balb/c mice. Collectively, AhR’s genomic regulation of FAK/RhoA, together with RhoA activation, is ascribable to the anti-migration effect of 3MC in HUVECs.     

Physiogenomic resources for rat models of heart, lung and blood disorders

Cardiovascular disorders are influenced by genetic and environmental factors. The TIGR rodent expression web-based resource (TREX) contains over 2,200 microarray hybridizations, involving over 800 animals from 18 different rat strains. These strains comprise genetically diverse parental animals and a panel of chromosomal substitution strains derived by introgressing individual chromosomes from normotensive Brown Norway (BN/NHsdMcwi) rats into the background of Dahl salt sensitive (SS/JrHsdMcwi) rats. The profiles document gene-expression changes in both genders, four tissues (heart, lung, liver, kidney) and two environmental conditions (normoxia, hypoxia). This translates into almost 400 high-quality direct comparisons (not including replicates) and over 100,000 pairwise comparisons. As each individual chromosomal substitution strain represents on average less than a 5% change from the parental genome, consomic strains provide a useful mechanism to dissect complex traits and identify causative genes. We performed a variety of data-mining manipulations on the profiles and used complementary physiological data from the PhysGen resource to demonstrate how TREX can be used by the cardiovascular community for hypothesis generation.     

Inhibition of Rho-associated kinase relieves C5a-induced proteinuria in murine nephrotic syndrome

Childhood nephrotic syndrome is mainly caused by minimal change disease which is named because only subtle ultrastructural alteration could be observed at electron microscopic level in the pathological kidney. Glomerular podocytes are presumed to be the target cells whose protein sieving capability is compromised by a yet unidentified permeability perturbing factor. In a cohort of children with non-hereditary idiopathic nephrotic syndrome, we found the complement fragment C5a was elevated in their sera during active disease. Administration of recombinant C5a induced profound proteinuria and minimal change nephrotic syndrome in mice. Purified glomerular endothelial cells, instead of podocytes, were demonstrated to be responsible for the proteinuric effect elicited by C5a. Further studies depicted a signaling pathway involving Rho/Rho-associated kinase/myosin activation leading to endothelial cell contraction and cell adhesion complex breakdown. Significantly, application of Rho-associated kinase inhibitor, Y27632, prevented the protein leaking effects observed in both C5a-treated purified endothelial cells and mice. Taken together, our study identifies a previously unknown mechanism underlying nephrotic syndrome and provides a new insight toward identifying Rho-associated kinase inhibition as an alternative therapeutic option for nephrotic syndrome.     

The development of allergic inflammation

Allergic disorders, such as anaphylaxis, hay fever, eczema and asthma, now afflict roughly 25% of people in the developed world. In allergic subjects, persistent or repetitive exposure to allergens, which typically are intrinsically innocuous substances common in the environment, results in chronic allergic inflammation. This in turn produces long-term changes in the structure of the affected organs and substantial abnormalities in their function. It is therefore important to understand the characteristics and consequences of acute and chronic allergic inflammation, and in particular to explore how mast cells can contribute to several features of this maladaptive pattern of immunological reactivity.     

上市公司经营活动状况对金融资产规模影响探究

越来越多的非金融业上市公司开始参与金融投资.通过实证研究来探索非金融业上市公司经营状况对其金融资产投资规模的影响,发现上市公司的金融资产有显著规模效应,同一行业内经营活动状况较好的上市公司有较少的金融投资,经营活动收入稳定增长的上市公司有较少的金融投资.