In the auditory system, the mechanotransduction (MT) ion channel is responsible for converting mechanical signal to electrical signal that can be sensed and processed by the brain. In the past several decades, the components composing the MT ion channel have been partly revealed. Among the MT complex components, TMIE plays an important role in maintaining mechanotransduction in auditory hair cells. Previous studies show that the C-terminus of TMIE is the interaction domain with other MT components, but the functions of N-terminus and the number of transmembrane domains are still unclear. In addition, it is reported that E31G mutation (in the N-terminus) in human TMIE could cause profound deafness, but the underlying mechanism is unknown. To understand whether the N-terminus contains a s...[ Read more ]

In the auditory system, the mechanotransduction (MT) ion channel is responsible for converting mechanical signal to electrical signal that can be sensed and processed by the brain. In the past several decades, the components composing the MT ion channel have been partly revealed. Among the MT complex components, TMIE plays an important role in maintaining mechanotransduction in auditory hair cells. Previous studies show that the C-terminus of TMIE is the interaction domain with other MT components, but the functions of N-terminus and the number of transmembrane domains are still unclear. In addition, it is reported that E31G mutation (in the N-terminus) in human TMIE could cause profound deafness, but the underlying mechanism is unknown. To understand whether the N-terminus contains a signal peptide and how E31G (E32G in mouse) mutation causes deafness, in my thesis study, I generated E32G mutation, T28K mutation— one predicted signal peptide cleavage site mutation, S34T35AA-mTMIE—two predicted O-linked glycosylation sites close to E32G, and Δ27-mTMIE— removing predicted signal peptide domain constructs. In my thesis study, I foud that E32G mutation has no effect on the O-linked glycosylation on the S34T35 site and TMIE cell-surface expression although it seemed to affect a unknown posttranslational modification of TMIE. By contrast, T28K mutation could disrupt signal peptide cleavage and TMIE cell-surface expression. I tentatively conclude that the signal peptide processing is necessary for TMIE trafficking to the plasma membrane, where it forms the functional component of MT complex. Taken together, my findings shed some new light on the function and regulation of TMIE.