Theile, J. W. | bioRxiv Science

bioRxiv2022

A-type FHFs mediate resurgent currents through TTX-resistant voltage-gated sodium channels

Resurgent currents (INaR) produced by voltage-gated sodium channels are required for many neurons to maintain high-frequency firing, and contribute to neuronal hyperexcitability and disease pathophysiology. Here we show, for the first time, that INaR can be reconstituted in a heterologous system by co-expression of sodium channel -subunits and A-type fibroblast growth factor homologous factors (FHFs). Specifically, A-type FHFs induces INaR from Nav1.8, Nav1.9 tetrodotoxin-resistant neuronal channels and, to a lesser extent, neuronal Nav1.7 and cardiac Nav1.5 channels. Moreover, we identified the N-terminus of FHF as the critical molecule responsible for A-type FHFs-mediated INaR. Among the FHFs, FHF4A is the most important isoform for mediating Nav1.8 and Nav1.9 INaR. In nociceptive sensory neurons, FHF4A knockdown significantly reduces INaR amplitude and the percentage of neurons that generate INaR, substantially suppressing excitability. Thus, our work reveals a novel molecular mechanism underlying TTX-resistant INaR generation and provides important potential targets for pain treatment.

neuroscience↗

bioRxiv2021

Robust W1282X-CFTR rescue by a small molecule GSPT1 degrader

With the approval of elexacaftor/tezacaftor/ivacaftor (trade name Trikafta), the vast majority of people with cystic fibrosis (CF) are eligible for CF transmembrane conductance regulator (CFTR) modulator therapy. Remaining individuals have premature termination codons or rare CFTR variants with limited treatment options. Although clinical modulator response can be reliably predicted using primary airway epithelial cells, primary cells carrying rare CFTR variants are scarce. To overcome this obstacle, these cells can be expanded by overexpression of mouse Bmi-1 and human TERT (hTERT). We therefore used this approach to develop two non-CF and three CF (F508del/F508del, F508del/S492F, W1282X/W1282X) nasal cell lines and two W1282X/W1282X bronchial cell lines. Bmi-1/hTERT cell lines recapitulated primary cell morphology and ion transport function. The F508del/F508del and F508del/S492F cell lines robustly responded to Trikafta, which was mirrored in the parent primary cells and the cell donors clinical response. CC-90009, a novel cereblon E3 ligase modulator targeting the GSPT1 protein, rescued ~20% of wildtype CFTR function in our panel of W1282X/W1282X cell lines and primary cells. Intriguingly, CC-90009 also diminished epithelial sodium channel function. These studies demonstrate that Bmi-1/hTERT cell lines faithfully mirror primary cell responses to CFTR modulators and illustrate novel therapeutic approaches for the W1282X CFTR variant.

pathology↗