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1.
Congenital muscular dystrophies (CMD) such as muscle–eye–brain disease caused by defective glycosylation of α-dystroglycan (α-DG) exhibit defective photoreceptor synaptic function. Mouse knockouts of dystroglycan and its extracellular matrix binding partner pikachurin recapitulate this phenotype. In this study, pikachurin–α-dystroglycan interactions in several mouse models of CMD were examined by pikachurin overlay experiments. The results show that hypoglycosylation of α-dystroglycan resulted in markedly reduced pikachurin–α-dystroglycan interactions. Expression of pikachurin is abolished at the outer plexiform layer of two mouse models, protein O-mannose N-acetylglucosaminyl transferase 1 (POMGnT1) knockout and Largemyd mice. Overexpressing LARGE restored this interaction in POMGnT1 knockout cells. These results indicate that pikachurin interactions with α-dystroglycan and its localization at the photoreceptor ribbon synapse require normal glycosylation of α-dystroglycan.  相似文献   
2.
Muscular dystrophies are a heterogeneous group of genetic disorders. In addition to genetic information, a combination of various approaches such as the use of genetic animal models, muscle cell biology, and biochemistry has contributed to improving the understanding of the molecular basis of muscular dystrophy's etiology. Several lines of evidence confirm that the structural linkage between the muscle extracellular matrix and the cytoskeleton is crucial to prevent the progression of muscular dystrophy. The dystrophin–glycoprotein complex links the extracellular matrix to the cytoskeleton, and mutations in the component of this complex cause Duchenne-type or limb-girdle-type muscular dystrophy. Mutations in laminin or collagen VI, muscle matrix proteins, are known to cause a congenital type of muscular dystrophy. Moreover, it is not only the primary genetic defects in the structural or matrix proteins, but also the primary mutations of enzymes involved in the protein glycosylation pathway that are now recognized to disrupt the matrix–cell interaction in a certain group of muscular dystrophies. This group of diseases is caused by the secondary functional defects of dystroglycan, a transmembrane matrix receptor. This review considers recent advances in understanding the molecular pathogenesis of muscular dystrophies that can be caused by the disruption of the cell–matrix linkage.  相似文献   
3.
Several forms of congenital muscular dystrophy result from mutations in glycosyltransferases that modify alpha-dystroglycan. As pontine hypoplasia has been reported in some clinical cases of congenital muscular dystrophy, we have begun to examine whether these glycosyltransferases are required for the normal development of the basilar pons, one of several precerebellar nuclei of the hindbrain. In veils (Large(vls)) mice, which carry a loss-of-function mutation in the Large glycosyltransferase gene, the basilar pons is absent. Instead, ectopic clusters of pontine neurons are found lateral to their normal site, suggesting that these neurons are unable to migrate to their appropriate site. Two other precerebellar nuclei, the lateral reticular nucleus and the inferior olive, are present in Large(vls) mice. In addition, the basilar pons forms normally in dystrophin-deficient mice. These results demonstrate that the Large glycosyltransferase but not dystrophin is required for normal basilar pontine development.  相似文献   
4.
The absence of dystrophin in muscle fibers is associated with a major reduction in dystrophin-associated proteins (DAPs) and disruption of the linkage between the subsarcolemmal cytoskeleton and the extracellular matrix. We investigated the expression of the DAPs β-dystroglycan, α-sarcoglycan, γ-sarcoglycan and syntrophin as well as utrophin in the muscles of 13 Duchenne muscular dystrophy (DMD) carriers (with variable percentages of dystrophin-deficient fibers and with a range of clinical symptoms), 2 Becker muscular dystrophy (BMD) carriers (expressing a highly truncated protein in some fibers), 2 girls with a DMD-like phenotype, and 11 BMD carriers with almost normal dystrophin expression (reduced or patchy distribution in a few fibers only and rare dystrophin-deficient fibers). DAPs were highly reduced in all fibers lacking dystrophin in the DMD carriers, but were almost normal in the dystrophin-deficient fibers of the 2 BMD carriers with highly truncated dystrophin. In the 11 BMD carriers with nearly normal dystrophin, the few fibers with reduced or patchy dystrophin immunostaining also showed reduced DAP expression in correlation with dystrophin expression. Immunoblot for β-dystroglycan and α-sarcoglycan confirmed the immunohistochemical findings. Utrophin expression was slightly increased in a proportion of fibers in the DMD and BMD carriers with dystrophin mosaicism. We found no correlation between utrophin expression and DAP expression. We conclude that absence or reduction of dystrophin in muscle fibers of DMD and BMD carriers causes a reduction of DAPs in the same fibers, as observed in DMD and BMD patients, while utrophin does not seem to play a role in DAP expression in adult muscle. Received: 11 January 1996 / Revised, accepted: 16 April 1996  相似文献   
5.
The possibility of using utrophin upregulation as a treatment for dystrophin-deficient muscular dystrophies has focused attention on the question of how many of dystrophin's various functions can be performed by the closely-related protein, utrophin. In Xenopus heart, little or no dystrophin was found on Western blots but the dystrophin-related protein, utrophin, was abundant. This utrophin was shown by immunofluorescence microscopy to be associated with cardiac muscle membranes and its distribution was similar to that of dystrophin in rabbit heart. The utrophin distribution pattern in the frog heart was shared by β-dystroglycan, a transmembrane protein responsible for localizing both dystrophin and utrophin at cell membranes. The results suggest that utrophin in Xenopus heart can perform similar functions to dystrophin in mammalian heart, lending further support to the possibility of utrophin upregulation therapy in muscular dystrophy. In skeletal muscle, however, Xenopus resembles mammals in expressing dystrophin at the sarcolemma and very little utrophin.  相似文献   
6.
目的:探讨口腔鳞癌细胞中β-DG蛋白的存在状态及其分子机制.方法:在检测口腔鳞癌四株细胞系中β-DG蛋白存在状态的基础上,应用Western blot和蛋白质测序法研究基质金属蛋白酶(MMP)抑制剂1,10-phenanthroline对β-DG蛋白降解和癌细胞侵袭能力的逆转作用.结果:口腔鳞癌细胞中β-DG蛋白发生了降解,经MMP抑制剂1,10-phenanthroline作用后可以逆转β-DG蛋白降解和降低癌细胞的侵袭能力.蛋白测序证实,β-DG蛋白降解片段N端的氨基酸顺序为Ile-Asn-Thr-Asn或Ile-Val-Thr-Gln.结论:口腔鳞癌细胞中β-DG蛋白降解与癌细胞的侵袭和转移能力有关,MMP的剪切作用可能是β-DG蛋白降解的重要机制之一.  相似文献   
7.
目的:探讨口腔鳞癌细胞中β-DG蛋白的存在状态及其分子机制。方法:在检测口腔鳞癌四株细胞系中β-DG蛋白存在状态的基础上,应用Western blot和蛋白质测序法研究基质金属蛋白酶(MMP)抑制剂1,10-phenanthroline对β-DG蛋白降解和癌细胞侵袭能力的逆转作用。结果:口腔鳞癌细胞中β-DG蛋白发生了降解,经MMP抑制剂1,10-phenanthroline作用后可以逆转β-DG蛋白降解和降低癌细胞的侵袭能力。蛋白测序证实,β-DG蛋白降解片段N端的氨基酸顺序为Ile-Asn-Thr-Asn或Ile-Val-Thr-Gln。结论:口腔鳞癌细胞中β-DG蛋白降解与癌细胞的侵袭和转移能力有关,MMP的剪切作用可能是β-DG蛋白降解的重要机制之一。  相似文献   
8.
The visceral glomerular epithelial cell, also known as the podocyte, plays an important role in the maintenance of renal glomerular function. This cell type is highly specialized and its foot processes together with the interposed slit diaphragm (SD) form the final barrier to urinary protein loss. Effacement of foot processes is associated with the development of proteinuria and—if not reversed in a certain time—with permanent deterioration of the glomerular filter. To maintain an intact glomerular filter barrier, podocyte-podocyte interactions and podocyte interactions with the glomerular basement membrane (GBM) are essential. Recent years have highlighted podocyte functions by unraveling the molecular composition of the SD, but have also clarified the important role of the podocyte actin cytoskeleton, and the podocyte-GBM interaction in the development of foot process (FP) effacement. This review provides an update of podocyte functions with respect to novel podocyte-specific proteins and also focuses on the dynamic interaction between the actin cytoskeleton of podocytes, their cell surface receptors and the GBM.  相似文献   
9.
The CT carbohydrate, Neu5Ac/Neu5Gcα2,3[GalNAcβ1,4]Galβ1,4GlcNAcβ-, is specifically expressed at the neuromuscular junction in skeletal myofibers of adult vertebrates. When Galgt2, the glycosyltransferase that creates the synaptic β1,4GalNAc portion of this glycan, is overexpressed in extrasynaptic regions of the myofiber membrane, α dystroglycan becomes glycosylated with the CT carbohydrate and this coincides with the ectopic expression of synaptic dystroglycan-binding proteins, including laminin α4, laminin α5, and utrophin. Here we show that both synaptic and extrasynaptic forms of laminin and agrin have increased binding to the CT carbohydrate compared to sialyl-N-acetyllactosamine, its extrasynaptically expressed precursor. Muscle laminins also show increased binding to CT-glycosylated muscle α dystroglycan relative to its non-CT-containing glycoforms. Overexpression of Galgt2 in transgenic mouse skeletal muscle increased the mRNA expression of extracellular matrix (ECM) genes, including agrin and laminin α5, as well as utrophin, integrin α7, and neuregulin. Increased expression of ECM proteins in Galgt2 transgenic skeletal muscles was partially dependent on utrophin, but utrophin was not required for Galgt2-induced changes in muscle growth or neuromuscular development. These experiments demonstrate that overexpression of a synaptic carbohydrate can increase both ECM binding to α dystroglycan and ECM expression in skeletal muscle, and they suggest a mechanism by which Galgt2 overexpression may inhibit muscular dystrophy and affect neuromuscular development.  相似文献   
10.
目的 观察大鼠神经鞘瘤细胞(RT4)中肌营养不良蛋白聚糖复合物的表达状况。方法 常规培养RT4细胞。应用免疫荧光染色,蛋白电泳,免疫印迹等方法观察肌营养不良蛋白聚糖复合体在RT4细胞中的表达并鉴定分子量。结果 肌营养不良蛋白聚糖复合体表达于RT4细胞的细胞膜上,结论 肌营养不良蛋白聚糖复合体对于RT4细胞与基底膜的连接起着重要的作用。  相似文献   
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