Global Analysis of Protein Expression of Inner Ear Hair Cells.

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Global Analysis of Protein Expression of Inner Ear Hair Cells.

J Neurosci. 2016 Dec 30;:

Authors: Hickox AE, Wong AC, Pak K, Strojny C, Ramirez M, Yates JR, Ryan AF, Savas JN

Abstract
The mammalian inner ear subserves auditory and vestibular sensations via highly specialized cells and proteins. Sensory receptor hair cells (HCs) are necessary for transducing mechanical inputs and stimulating sensory neurons by employing a host of known and yet unknown protein machinery. To understand the protein composition of these unique post-mitotic cells, in which irreversible protein degradation or damage can lead to impaired hearing and balance, we analyzed inner ear samples by tandem mass spectrometry to generate an unbiased, shotgun-proteomics view of protein identities and abundances. By using Pou4f3/eGFP transgenic mice, in which HCs express GFP driven by Pou4f3, we FACS-purified a population of HCs to analyze and compare the HC proteome with other inner ear sub-proteomes from sensory epithelia and whole inner ear. We show that the mammalian HC proteome comprises hundreds of uniquely or highly expressed proteins. Our global proteomic analysis of purified HCs extends the existing HC transcriptome, revealing previously undetected gene products and isoform-specific protein expression. Comparison of our proteomic data with mouse and human databases of genetic auditory/vestibular impairments confirms the critical role of the HC proteome for normal inner ear function, providing a cell-specific pool of candidates for novel, important HC genes. Several proteins identified exclusively in HCs by proteomics and verified by immunohistochemistry map to human genetic deafness loci, potentially representing new deafness genes.
SIGNIFICANCE STATEMENT: Hearing and balance rely on specialized sensory hair cells (HCs) in the inner ear to convey information about sound, acceleration and orientation to the brain. Genetically and environmentally induced perturbations to HC proteins can result in deafness and severe imbalance. We used transgenic mice with GFP-expressing HCs, coupled with FACS-sorting and tandem mass spectrometry, to define the most complete HC-, and inner ear-, proteome to-date. We show that hundreds of proteins are uniquely identified or enriched in HCs, extending previous gene expression analyses to reveal novel HC proteins and isoforms. Importantly, deafness-linked proteins were significantly enriched in HCs, suggesting that this in-depth proteomic analysis of inner ear sensory cells may hold potential for deafness gene discovery.

PMID: 28039372 [PubMed - as supplied by publisher]

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