Role of Cytoplasmic Actin Isoforms in the Inner Ear

描述(申请人提供)：肌动蛋白是自然界中含量最丰富的蛋白质之一，在几乎所有细胞功能中都扮演着重要的角色，包括肌肉收缩、细胞迁移、囊泡运输和极化生长。有两种胞质肌动蛋白亚型，即细胞肌动蛋白和细胞肌动蛋白，广泛表达。虽然这些细胞质肌动蛋白亚型由不同的基因编码，但在375个氨基酸残基中只有4个氨基酸残基不同；然而，这些小的序列差异在鸟类和哺乳动物之间是保守的，这表明细胞和细胞肌动蛋白具有不同的细胞功能。与这一观点一致，细胞肌动蛋白和细胞肌动蛋白的细胞定位不同，这被认为是导致细胞极化的原因。此外，一些细胞肌动蛋白突变会导致人类进行性耳聋，这表明这种异构体的重要细胞作用是细胞肌动蛋白无法填补的。尽管在了解肌动蛋白如何受其他蛋白质调控方面已经取得了令人印象深刻的进展，但肌动蛋白和细胞肌动蛋白的不同功能仍然知之甚少。该研究的目标包括阐明哺乳动物内耳中细胞肌动蛋白和细胞肌动蛋白的具体功能。初步证据表明，细胞肌动蛋白缺陷小鼠表现出进行性听力损失。将产生一只细胞肌动蛋白缺陷小鼠，以比较细胞肌动蛋白缺陷和细胞肌动蛋白缺陷对听觉生理学的影响。此外，两种模型的极化内耳细胞的结构和功能将通过光学和电子显微镜进行分析，以了解听力变化背后的细胞机制。该奖学金将通过进一步了解细胞肌动蛋白和细胞肌动蛋白对正常细胞生物学的不同贡献，为改善公共卫生做出贡献。此外，由人类细胞肌动蛋白9烯突变引起的进行性耳聋与细胞肌动蛋白缺陷小鼠的表型相似，其特征可能有助于深入了解这种形式的人类耳聋的病理机制。

DESCRIPTION (provided by applicant): Actin is one of the most abundant proteins in nature and plays essential roles in almost every cellular function including muscle contraction, cell migration, vesicle trafficking, and polarized growth. Two cytoplasmic actin isoforms, ¿cyto- and ?cyto-actin, are ubiquitously expressed. Although encoded by separate genes, these cytoplasmic actin isoforms vary at only 4 of 375 amino acid residues; however, these small sequence differences are conserved between birds and mammals, suggesting that ¿cyto-- and ?cyto-actin nave distinct cellular functions. Consistent with this idea, the cellular localization of ¿cyto-- and ?cyto-actin differ, which is thought to contribute to cell polarization. Additionally, some ?cyto-actin mutations lead to progressive deafness in humans, indicating an essential cellular role for this isoform that cannot be filled by ¿cyto-actin. Although impressive gains have been made in understanding how actins are regulated by other proteins, the distinct functions of ¿- and ?cyto--actin remain poorly understood. The goals of this fellowship include elucidating the specific functions of ¿cyto- and ?cyto--actin in the mammalian inner ear. Preliminary evidence suggests that ?cyto--actin deficient mice display progressive hearing loss. A ¿cyto-actin-deficient mouse will be generated to allow for a comparison of the effect ¿cyto- and ?cyto-actin deficiency on auditory physiology. Additionally, the structure and function of polarized inner ear cells in both models will be analyzed by both light and electron microscopy to understand the cellular mechanism underling changes in hearing. This fellowship will contribute to improving public health by furthering understanding of the distinct contributions of ¿cyto- and ?cyto--actin to normal cell biology. Additionally, progressive deafness caused by mutation of the human ?cyto-actin 9ene is Paralleled by the phenotype of the ?cyto--actin deficient mouse, characterization of which will likely provide insight into the pathomechanism of this form of human deafness.