Biology subjects

Mu, T.-W.

Publications and source records attributed to Mu, T.-W..

3 recordsLinked to original sources

bioRxiv2023

Pharmacological chaperones restore proteostasis of epilepsy-associated GABAA receptor variants

Recent advances in genetic diagnosis identified variants in genes encoding GABAA receptors as causative for genetic epilepsy. Here, we selected eight disease-associated variants in the 1 subunit of GABAA receptors causing mild to severe clinical phenotypes and showed that they are loss of function, mainly by reducing the folding and surface trafficking of the 1 protein. Furthermore, we sought client protein-specific pharmacological chaperones to restore the function of pathogenic receptors. Applications of positive allosteric modulators, including Hispidulin and TP003, increase the functional surface expression of the 1 variants. Mechanism of action study demonstrated that they enhance the folding and assembly and reduce the degradation of GABAA variants without activating the unfolded protein response in HEK293T cells and human iPSC-derived neurons. Since these compounds cross the blood-brain barrier, such a pharmacological chaperoning strategy holds great promise to treat genetic epilepsy in a GABAA receptor-specific manner.

cell biology↗

bioRxiv2022

Hsp47 Promotes Biogenesis of Multi-subunit Neuroreceptors in the Endoplasmic Reticulum

Protein homeostasis (proteostasis) deficiency is an important contributing factor to neurodegenerative, neurological, and metabolic diseases. However, how the proteostasis network orchestrates the folding and assembly of multi-subunit membrane proteins is not well understood. Previous proteomics studies identified Hsp47 (Gene: SERPINH1), a heat shock protein in the endoplasmic reticulum lumen, as the most enriched interacting chaperone for gamma-aminobutyric type A (GABAA) receptors. Here, we show that Hsp47 enhances neuronal GABAA receptor functional surface expression, acting after Binding immunoglobulin Protein (BiP) to preferentially bind the folded conformation of GABAA receptors. Therefore, Hsp47 promotes the subunit-subunit interaction, the receptor assembly process, and the anterograde trafficking of GABAA receptors. These Hsp47 properties are also extended to other Cys-loop receptors, including nicotinic acetylcholine receptors. Therefore, in addition to its known function as a collagen chaperone, this work establishes that Hsp47 also plays a critical and general role in the maturation of multi-subunit neuroreceptors. HighlightsO_LIHsp47 positively regulates the functional surface expression of endogenous GABAA receptors. C_LIO_LIHsp47 acts after BiP and preferentially binds the folded conformation of GABAA receptors. C_LIO_LIHsp47 promotes the subunit-subunit assembly of GABAA receptors. C_LIO_LIHsp47 plays a critical and general role in the maturation of multi-subunit neuroreceptors. C_LI

cell biology↗

bioRxiv2022

The Endoplasmic Reticulum Membrane Complex Promotes Proteostasis of GABAA Receptors

The endoplasmic reticulum membrane complex (EMC) plays a critical role in the biogenesis of tail-anchored and a subset of multi-pass membrane proteins in the endoplasmic reticulum. However, due to the nearly exclusive expression of neurotransmitter-gated ion channels in the central nervous system, the role of the EMC in their biogenesis is not well understood. In this study, we demonstrated that the EMC positively regulates the surface trafficking and thus function of endogenous {gamma}-aminobutyric acid (GABAA) receptors, the primary inhibitory ion channels in the mammalian brain. Further, among ten EMC subunits, EMC3 and EMC6 have the most prominent effects, indicating a subunit-specific contribution. EMC3 and EMC6 show endogenous interactions with major neuroreceptors, which depends on their transmembrane domains. Overexpression of EMC3 and EMC6 is sufficient to restore the function of epilepsy-associated GABAA receptor variants, suggesting that operating EMC has the potential to ameliorate neurological diseases associated with protein conformational defects. In briefThe multi-subunit EMC serves as an insertase for a subset of membrane proteins and enables their biogenesis in the endoplasmic reticulum. However, the subunit-specific effect of the EMC on multi-pass neuroreceptors is not well understood. Whittsette et al. demonstrate that EMC3 and EMC6 interact with GABAA receptors and positively regulate their trafficking and function. HighlightsO_LIEMC3 and EMC6 positively regulate the function of endogenous GABAA receptors. C_LIO_LIThe EMC interacts with major endogenous neuroreceptors. C_LIO_LIThe interaction between EMC and GABAA receptors depends on the EMC transmembrane domains. C_LIO_LIOverexpressing the EMC is sufficient to restore the function of pathogenic GABAA receptor variants. C_LI

cell biology↗