Project Details
Projekt
The role of transmembrane protein 145 (TMEM 145) in cochlear function and sensory hearing loss
Subject Area
Otolaryngology, Phoniatrics and Audiology
Term
since 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 544132987
Hearing loss affects more than 5% of the global population and significantly impacts on psychosocial well-being, communication, and work capabilities. Hearing loss mostly stems from the deterioration of auditory sensory hair cells. The cochlea houses two hair cell types: inner hair cells (IHCs) as primary sensory receptors, and outer hair cells (OHCs) crucial for sound amplification. A unique aspect of OHCs is their mechanical stimulation through a direct connection to the tectorial membrane via a protein complex termed ‘tectorial membrane attachment crown’ (TM-AC). Known components of TM-ACs are the secreted proteins stereocilin, otogelin, and otogelin-like. Mutations or deletion of these genes result in hearing loss in humans and mice, respectively. The intracellular membrane adaptor protein tubby colocalizes with the TM-AC and mutations of tubby result in loss of the TM-ACs from the OHC stereocilia. This impact of tubby on TM-AC proteins predicts the presence of an additional, so far unknown, transmembrane protein, mediating the interaction across the stereocilia membrane. We observed that TMEM145, a GPCR-related transmembrane protein, specifically colocalizes with TM-ACs. Mice lacking TMEM145 show hearing loss that phenocopies stereocilin and tubby mutants. Here, we aim to uncover the role of TMEM145 in the stereocilia of OHCs, particularly with respect to the TM-ACs. We will therefore examine the spatial distribution of TMEM145 in the hair bundle and in relation to the known components of the TM-AC complex by superresolution microscopy. To address the role of TMEM145 for assembly, maintenance, or targeting of TM-ACs as well as its impact on overall hair bundle structure, we will study changes in OHCs from TMEM145 knockout mice by conventional fluorescence microscopy, superresolution microscopy, and electron microscopy. Presumptive direct interactions of TMEM145 with components of the TM-AC will be analyzed using biochemical binding assays and by reconstitution of the complex in heterologous expression systems. The impact of loss of TMEM145 on hair cell function will be addressed by patch-clamp electrophysiology and live-cell imaging. Additionally, we will explore the implications of TMEM145 in age-dependent hearing loss and noise trauma in knockout mice. Finally, we will screen for TMEM145 mutations underlying human deafness. We expect that our results will provide an improved understanding of TMEM145- and TM-AC-related hearing loss in humans, with implications for the prevention and future treatments of hearing loss.
DFG Programme
Research Grants
Co-Investigator
Professor Dr. Dominik Oliver
