Gontier Yves, Taivainen Anu, Fontao Lionel, Sonnenberg Arnoud, van der Flier Arjan, Carpen Olli, Faulkner Georgine, Borradori Luca
Department of Dermatology, University Hospital, HUG, Rue Micheli-du-Crest 24, 1211 Geneva 14 Switzerland.
J Cell Sci. 2005 Aug 15;118(Pt 16):3739-49. doi: 10.1242/jcs.02484. Epub 2005 Aug 2.
Myotilin and the calsarcin family member FATZ-1 (also called calsarcin-2 or myozenin-1) are recently discovered sarcomeric proteins implicated in the assembly and stabilization of the Z-discs in skeletal muscle. The essential role of myotilin in skeletal muscle is attested by the observation that certain forms of myofibrillar myopathy and limb girdle muscular dystrophy are caused by mutations in the human myotilin gene. Here we show by transfection, biochemical and/or yeast two-hybrid assay that: (1) myotilin is able to interact with the C-terminal region of FATZ-1 and that the N- or C-terminal truncations of myotilin abrogate binding; (2) myotilin can also interact with another calsarcin member, FATZ-2 (calsarcin-1, myozenin-2); (3) myotilin and FATZ-1 bind not only to the C-terminal region of filamin-C containing the Ig repeats 19-24, but also to the other two filamins, filamin-A and filamin-B, as well as the newly identified filamin-Bvar-1variant; (4) the binding of myotilin to filamin-C involves binding sites in its N-terminal region, whereas FATZ-1 associates with filamin-C via sequences within either its N- or C-terminal region; and finally, (5) the C-terminal region of filamin-C like filamin-B and filamin-Bvar-1, shows binding activity with the beta1A integrin subunit. Our findings further dissect the molecular interactions within the Z-disc that are essential for its organization, and provide evidence for a novel connection between Z-disc proteins and the sarcolemma via filamins and beta1 integrins. These data shed new light on the complex organization of the Z-disc that is highly relevant to understanding muscular dystrophies.
肌联蛋白和肌钙蛋白家族成员FATZ-1（也称为肌钙蛋白-2或肌联蛋白-1）是最近发现的肌节蛋白，与骨骼肌中Z盘的组装和稳定有关。某些形式的肌原纤维肌病和肢带型肌营养不良是由人类肌联蛋白基因突变引起的，这一观察结果证明了肌联蛋白在骨骼肌中的重要作用。在这里，我们通过转染、生化和/或酵母双杂交试验表明：（1）肌联蛋白能够与FATZ-1的C末端区域相互作用，而肌联蛋白的N末端或C末端截短会消除这种结合；（2）肌联蛋白还可以与另一种肌钙蛋白成员FATZ-2（肌钙蛋白-1，肌联蛋白-2）相互作用；（3）肌联蛋白和FATZ-1不仅与包含免疫球蛋白重复序列19-24的细丝蛋白C的C末端区域结合，还与另外两种细丝蛋白细丝蛋白A和细丝蛋白B以及新鉴定的细丝蛋白Bvar-1变体结合；（4）肌联蛋白与细丝蛋白C的结合涉及其N末端区域的结合位点，而FATZ-1通过其N末端或C末端区域内的序列与细丝蛋白C结合；最后，（5）细丝蛋白C的C末端区域与细丝蛋白B和细丝蛋白Bvar-1一样，显示出与β1A整合素亚基的结合活性。我们的研究结果进一步剖析了Z盘中对其组织至关重要的分子相互作用，并为Z盘蛋白与肌膜之间通过细丝蛋白和β1整合素建立的新联系提供了证据。这些数据为Z盘的复杂组织提供了新的线索，这与理解肌营养不良症高度相关。
