Cystic fibrosis (CF) is a lethal autosomal recessive inherited disease caused by the loss or dysfunction of the CF transmembrane conductance regulator (CFTR) Cl- channel activity resulting from mutations. Clinically, chronic lung disease is the main cause of morbidity and mortality for CF patients. Among the 1900+ disease- causing mutations, c.1521_1523delCTT (F508del) is the most common mutation and associates with a severe form of CF disease. The ideal therapy for CF associated with F508del requires an increase in the quantity of protein at the cell surface, to potentiate the impaired channel gating properties and to improve protein stability. This notion was supported by promising results from clinical trials on CF patients with F508del, which demonstrated that a combinational approach using VX-809 (a CFTR corrector) and ivacaftor (a CFTR potentiator) led to significant improvements in the lung function of the study subjects. In this proposal, we plan to study a previously unrecognized inhibitory protein complex containing the rescued F508del-CFTR, Na+/H+ exchanger regulator factor-2 (NHERF2) and type-2 lysophosphatidic acid receptor (LPA2), and to pharmacologically disrupt this complex to increase F508del-CFTR channel function. The unifying hypothesis to be tested is that (i) the rescued F508del-CFTR, like wild type CFTR, forms an inhibitory complex with NHERF2 and LPA2 at the plasma membrane;(ii) disruption of this complex by specifically disrupting the NHERF2-LPA2 interaction will potentiate the channel function of F508del-CFTR;(iii) because the molecular mechanism underlying the disruption of NHERF2-LPA2 interaction is independent of that underlying the effect of VX-809 or VX-770, the NHERF2-LPA2 inhibitors can have additive or synergistic effects with VX-809 and VX-770 on augmentation of F508del-CFTR channel function. The proposed study will not only unveil a previously unrecognized protein complex that inhibits F508del-CFTR channel function, but will also provide a novel approach to augmenting F508del-CFTR channel function by abrogating this inhibitory signaling. Because, in addition to F508del, a variety of other CFTR mutations can also form complexes with NHERF2 and LPA2, the approach we propose could have a broad spectrum potentiating effect on CFTR mutations. Therefore, our study will expand our knowledge of the CFTR interactome and help us better understand the pathobiology of F508del-CFTR at the cell surface. Furthermore, our disruptor approach may open up a new avenue for developing drugs to treat CF associated with a variety of mutations.
We propose to study an inhibitory protein complex containing the rescued F508del-CFTR. We will also explore the therapeutic manipulation of this complex to increase F508del-CFTR channel function. The study will expand our knowledge of the CFTR interactome and help us better understand the pathobiology of F508del- CFTR at the cell surface, and might pave the way to novel cystic fibrosis therapies.