Regulation of signal transduction of TGF-β family by novel adaptor and binding proteins

我们分析了受体相关的衔接蛋白和结合蛋白对肌生长抑制素和激活素信号的调控。肌生长抑制素和激活素属于TGF-β超家族，通过激活素II型受体（ActRIIs）发出信号，激活素II型受体是受体丝氨酸/苏氨酸激酶。在TGF-β家族的其他受体丝氨酸激酶中，ActRIIs是独一无二的，因为它们在其羧基端具有PDZ蛋白的一致结合基元。我们已经确定了多种PDZ蛋白，称为与actrii相关的激活素受体相互作用蛋白（ARIPs）。ARIP1是一种具有5个PDZ结构域和2个WW结构域的大蛋白，不仅与ActRIIs结合，还与谷氨酸受体和酪氨酸激酶src家族结合。ARIP2是一种只有一个PDZ结构域的小蛋白。我们已经确定ARIP2至少有四个剪接变体，ARIP2, 2b， 2c和OMP25，它们是由来自一个基因的替代RNA剪接事件形成的。而ARIP2则通过RalBP1依赖通路增强ActRII的内吞作用，抑制激活素/肌肉生长抑制素信号传导，而ARIP2b和2c则不与RalBP1相关。arip2b /2c增加细胞表面的ActRIIs水平，增强信号传导。我们还分析了卵泡抑素和FLRG，它们是肌肉生长抑制素和激活素的结合蛋白。与卵泡抑素一样，FLRG也在子宫和胎盘中表达，但性类固醇调节FLRG表达的方式与卵泡抑素不同。在小鼠骨骼肌中，FLRG在慢型肌纤维中特异性表达。FLRG可能调节血清和局部骨骼肌组织中的肌肉生长抑制素活性。我们已经从卵泡抑素中提取了各种人造蛋白，并鉴定了几种肌生成抑素特异性抑制剂。我们已经制造出过表达一种肌生成抑制素特异性抑制剂的转基因小鼠。小鼠骨骼肌质量增加。当与mdx营养不良模型小鼠杂交时，mdx小鼠的纤维化和脂肪重塑等病理改变被阻止，这表明我们的肌肉生长抑制素抑制剂将是治疗肌肉营养不良和其他肌肉萎缩疾病的良好药物。少

We have analyzed the regulation of myostatin and activin signaling by receptor associated adaptor proteins and binding proteins. Myostatin and activin belong to the TGF-β superfamily and signal through activin type II receptors (ActRIIs) that are receptor serine/threonine kinases. ActRIIs are unique among other receptor serine kinases for the TGF-β family in that they have consensus binding motifs for PDZ proteins at their carboxy terminus. We have identified multiple PDZ proteins, called activin receptor-interacting proteins (ARIPs) that associate with ActRIIs. ARIP1 is a large protein having five PDZ domains and two WW domains, and associates not only with ActRIIs but also with glutamate receptors and src family of tyrosine kinases. ARIP2 is a small protein that has only one PDZ domain. We have identified ARIP2 has at least four splicing variants, ARIP2, 2b, 2c and OMP25 that are formed by alternative RNA splicing events from one gene. Whereas ARIP2 enhances endocytosis of ActRII thr … More ough Ral/RalBP1-dependent pathway and inhibit activin/myostatin signaling, ARIP2b and 2c do not associate with RalBP1. ARIP 2b/2c increase cell surface level of ActRIIs and augment signaling.We also analyzed follistatin and FLRG that are binding proteins for myostatin and activin. Like follistatin, FLRG is expressed in uterus and placenta, but mode of regulation of FLRG expression by sex steroids are different from that of follistatin. In mouse skeletal muscles, FLRG is specifically expressed in slow type muscle fibers. FLRG is likely to regulate myostatin activity in serum as well as in skeletal muscle tissues locally. We have made various artificial protein derived from follistatin, and identified several myostatin-specific inhibitors. We have made transgenic mouse that overexpress one of myostatin-specific inhibitors. The mice show increase of skeletal muscle mass. When crossed with mdx dystrophy model mice, pathological changes such as fibrosis and fatty remodeling seen in mdx mice were prevented, suggesting that our myostatin inhibitors would be a good drugs for treatment of muscular dystrophy and other muscle-wasting disorders. Less