Cystic Fibrosis (CF), the most common lethal autosomic recessive disorder among Caucasians, is caused by mutations in the gene encoding the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) protein, a cAMP-regulated chloride channel expressed at the apical surface of epithelial cells. Cyclic AMP regulates both CFTR channel gating through a protein kinase A (PKA)-dependent process and plasma membane (PM) stability through activation of the exchange protein directly activated by cAMP1 (EPAC1). This cAMP effector, when activated promotes the NHERF1:CFTR interaction leading to an increase in CFTR at the PM by decreasing its endocytosis. Here, we used protein interaction profiling and bioinformatic analysis to identify proteins that interact with CFTR under EPAC1 activation as possible regulators of this CFTR PM anchoring. We identified an enrichment in cytoskeleton related proteins among which we characterized CAPZA2 and INF2 as regulators of CFTR trafficking to the PM. We found that CAPZA2 promotes wt-CFTR trafficking under EPAC1 activation at the PM whereas reduction of INF2 levels leads to a similar trafficking promotion effect. These results suggest that CAPZA2 is a positive regulator and INF2 a negative one for the increase of CFTR at the PM after an increase of cAMP and concomitant EPAC1 activation. Identifying the specific interactions involving CFTR and elicited by EPAC1 activation provides novel insights into late CFTR trafficking, insertion and/or stabilization at the PM and highlighs new potential therapeutic targets to tackle CF disease.

中文翻译：

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细胞骨架调节剂CAPZA2和INF2与CFTR结合，以在EPAC1激活下控制其质膜水平。

囊性纤维化（CF）是高加索人中最常见的致死性常染色体隐性遗传疾病，是由编码囊性纤维化跨膜电导调节剂（CFTR）蛋白的基因突变引起的，该蛋白是cAMP调节的上皮细胞顶表面表达的氯离子通道。环状AMP通过激活直接由cAMP1（EPAC1）激活的交换蛋白来调节通过蛋白激酶A（PKA）依赖性过程的CFTR通道门控和血浆膜（PM）的稳定性。当激活时，此cAMP效应子会促进NHERF1：CFTR相互作用，从而通过减少其内吞作用而导致PM处CFTR的增加。在这里，我们使用蛋白质相互作用分析和生物信息学分析来鉴定在EPAC1激活下与CFTR相互作用的蛋白，作为CFTR PM锚定的可能调节剂。我们确定了丰富的细胞骨架相关蛋白，其中我们将CAPZA2和INF2表征为CFTR转运至PM的调节剂。我们发现，CAPZA2在PM激活EPAC1的情况下促进wt-CFTR的运输，而INF2水平的降低导致类似的运输促进作用。这些结果表明，CAPZA2是一个正调控因子，而INF2是一个负调控因子，在cAMP和伴随的EPAC1激活增加后，PM处CFTR的增加。鉴定涉及CFTR并由EPAC1激活引起的特定相互作用，可提供对CFTR后期运输，在PM处插入和/或稳定化的新见解，并为应对CF疾病提供了新的潜在治疗靶标。