Acidic and basic troponin T isoforms in mature fast-twitch skeletal muscle and effect on contractility.
Acidic and basic troponin T isoforms in mature fast-twitch skeletal muscle and effect on contractility.
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DOI：
10.1152/ajpcell.1999.276.5.c1162
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发表时间：
1999-05
期刊：
影响因子：
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通讯作者：
O. Ogut;H. Granzier;Jian-Ping Jin
中科院分区：
文献类型：
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作者：
O. Ogut;H. Granzier;Jian-Ping Jin
发育调节的可变RNA剪接产生不同类型的酸性和碱性肌钙蛋白T（TnT）亚型。在快速收缩的骨骼肌中，酸性到碱性TnT同种型的转换确保了成人的基本同种型表达。作为例外，成年鸡胸肌TnT同种型的NH 2-末端可变区中的酸性区段负责酸性TnT在该肌肉中的独特排他表达（O. Ogut和J. - P. Jin。273：27858-27866，1998）。为了了解酸性与碱性TnT亚型表达和肌肉收缩之间的关系，将来自成年鸡胸脯肌的纤维的收缩特性与仅表达碱性TnT亚型的提尾肌的收缩特性进行比较。使用Triton X-100皮肤的肌纤维，力和刚度响应Ca 2+进行了测量。相对于提尾肌，胸肌纤维对力和刚度的Ca 2+的敏感性显着增加，力或刚度为最大值的50%时，pCa的变化为1.0015。原肌球蛋白、肌钙蛋白I和肌钙蛋白C亚型的表达也被确定，以描述它们对细丝调节的贡献。这些数据表明，不同的肌钙蛋白T亚型在其NH 2-末端电荷能够改变的肌原纤维收缩装置的敏感性Ca 2+。这些结果提供了证据连接不同的酸性和碱性TnT亚型类横纹肌的收缩性的调节表达。
Developmentally regulated alternative RNA splicing generates distinct classes of acidic and basic troponin T (TnT) isoforms. In fast-twitch skeletal muscles, an acidic-to-basic TnT isoform switch ensures basic isoform expression in the adult. As an exception, an acidic segment in the NH2-terminal variable region of adult chicken breast muscle TnT isoforms is responsible for the unique exclusive expression of acidic TnTs in this muscle (O. Ogut and J.-P. Jin. J. Biol. Chem. 273: 27858-27866, 1998). To understand the relationship between acidic vs. basic TnT isoform expression and muscle contraction, the contractile properties of fibers from adult chicken breast muscle were compared with those of the levator coccygeus muscle, which expresses solely basic TnT isoforms. With use of Triton X-100-skinned muscle fibers, the force and stiffness responses to Ca2+ were measured. Relative to the levator coccygeus muscle, the breast muscle fibers showed significantly increased sensitivity to Ca2+ of force and stiffness with a shift of ∼0.15 in the pCa at which force or stiffness was 50% of maximal. The expression of tropomyosin, troponin I, and troponin C isoforms was also determined to delineate their contribution to thin-filament regulation. The data indicate that TnT isoforms differing in their NH2-terminal charge are able to alter the sensitivity of the myofibrillar contractile apparatus to Ca2+. These results provide evidence linking the regulated expression of distinct acidic and basic TnT isoform classes to the contractility of striated muscle.