Daudet Nicolas, Lebart Marie-Christine
INSERM UR 254, Laboratoire de Neurobiologie de l'Audition-Plasticité Synaptique, Montpellier, France.
Cell Motil Cytoskeleton. 2002 Dec;53(4):326-36. doi: 10.1002/cm.10092.
The transduction of auditory signals by cochlear hair cells depends upon the integrity of hair cell stereociliary bundles. Stereocilia contain a central core of actin filaments, cross-linked by actin bundling proteins. In the cochlea, the two proteins described to date as responsible for the spatial arrangement of actin filaments in sterocilia are fimbrin and the recently discovered espin. Fimbrin (the chick homolog of human I-plastin) belongs to the plastins/fimbrin family that includes two additional isoforms of plastins, T- and L-plastin. In the present study, we used isoform specific antibodies to investigate the presence of the T- and L-isoforms of plastin/fimbrin in the adult and developing rat cochlea. We found that T-plastin, but not L-plastin, is expressed in the rat cochlea. During postnatal development of the rat organ of Corti, T-plastin can be detected in the core of stereocilia from early stages of hair cell differentiation, and its expression gradually increases in stereocilia as hair cells mature. However, as opposed to other actin-binding proteins expressed in stereocilia, T-plastin is absent from the stereocilia of mature hair cells. Such temporally restricted expression strengthens the idea of functional differences between plastins isoforms, and suggests that T-plastin could have a specific role in stereocilia formation.
耳蜗毛细胞对听觉信号的转导依赖于毛细胞静纤毛束的完整性。静纤毛含有由肌动蛋白成束蛋白交联的肌动蛋白丝中央核心。在耳蜗中，迄今为止被描述为负责静纤毛中肌动蛋白丝空间排列的两种蛋白质是丝束蛋白和最近发现的espin。丝束蛋白（人类I-丝束蛋白的鸡同源物）属于丝束蛋白/丝束蛋白家族，该家族还包括丝束蛋白的另外两种异构体，即T-丝束蛋白和L-丝束蛋白。在本研究中，我们使用异构体特异性抗体来研究丝束蛋白/丝束蛋白的T-异构体和L-异构体在成年和发育中的大鼠耳蜗中的存在情况。我们发现T-丝束蛋白而非L-丝束蛋白在大鼠耳蜗中表达。在大鼠柯蒂氏器的出生后发育过程中，从毛细胞分化的早期阶段开始，就可以在静纤毛的核心中检测到T-丝束蛋白，并且随着毛细胞成熟，其在静纤毛中的表达逐渐增加。然而，与在静纤毛中表达的其他肌动蛋白结合蛋白不同，成熟毛细胞的静纤毛中不存在T-丝束蛋白。这种时间上受限的表达强化了丝束蛋白异构体之间功能差异的观点，并表明T-丝束蛋白可能在静纤毛形成中具有特定作用。
