KLF4 Acts as a wt-CFTR Suppressor through an AKT-Mediated Pathway

Luis Sousa,Karl Kunzelmann,Ines Pankonien,Iris Silva,Luka A Clarke,Margarida D Amaral

doi:10.3390/cells9071607

Luis Sousa, Karl Kunzelmann + Show 4 more

Open Access

https://doi.org/10.3390/cells9071607

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Journal: Cells	Publication Date: Jul 2, 2020
Citations: 14	License type: CC BY 4.0

Affiliation: University of Lisbon, University of Regensburg

Abstract

Cystic Fibrosis (CF) is caused by >2000 mutations in the CF transmembrane conductance regulator (CFTR) gene, but one mutation—F508del—occurs in ~80% of patients worldwide. Besides its main function as an anion channel, the CFTR protein has been implicated in epithelial differentiation, tissue regeneration, and, when dysfunctional, cancer. However, the mechanisms that regulate such relationships are not fully elucidated. Krüppel-like factors (KLFs) are a family of transcription factors (TFs) playing central roles in development, stem cell differentiation, and proliferation. Herein, we hypothesized that these TFs might have an impact on CFTR expression and function, being its missing link to differentiation. Our results indicate that KLF4 (but not KLF2 nor KLF5) is upregulated in CF vs. non-CF cells and that it negatively regulates wt-CFTR expression and function. Of note, F508del–CFTR expressing cells are insensitive to KLF4 modulation. Next, we investigated which KLF4-related pathways have an effect on CFTR. Our data also show that KLF4 modulates wt-CFTR (but not F508del–CFTR) via both the serine/threonine kinase AKT1 (AKT) and glycogen synthase kinase 3 beta (GSK3β) signaling. While AKT acts positively, GSK3β is a negative regulator of CFTR. This crosstalk between wt-CFTR and KLF4 via AKT/ GSK3β signaling, which is disrupted in CF, constitutes a novel mechanism linking CFTR to the epithelial differentiation.

Highlights

Cystic Fibrosis (CF) is the most common lethal genetic disease among Caucasians, with a variable geographic prevalence of 1:2500–6000 in Europe, according to the European Cystic Fibrosis Society registry [1]
We evaluated the expression of Krüppel-like factors (KLFs) in CFBE cells expressing wt- and F508del–CFTR at both RNA and protein levels (Figure 1B,C)
We investigated whether the Krüppel-like factors (KLFs), a family of evolutionary conserved zinc finger transcription factors that regulate a variety of biological processes including proliferation, differentiation, and apoptosis [6], have an impact on CFTR expression and function

Summary

Introduction

Cystic Fibrosis (CF) is the most common lethal genetic disease among Caucasians, with a variable geographic prevalence of 1:2500–6000 in Europe, according to the European Cystic Fibrosis Society registry [1]. Over 2000 mutations in the gene encoding the CF transmembrane conductance regulator (CFTR) protein have so far been reported, but the deletion of the phenylalanine at the position 508. (F508del) is by far the most common one, present in at least one allele in ~80% of individuals with. The F508del mutation impairs CFTR protein folding and plasma membrane (PM). The association of CFTR to epithelial differentiation has been described in several studies (reviewed recently in [3]). Being CFTR a chloride/bicarbonate channel, it is not expected to be a direct regulator of differentiation and epithelial regeneration. Such a role possibly relies on its positive/negative effect on transcriptional factors (TFs) that act at the nuclear level to regulate proliferation and

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