Rab GTPases regulate the trafficking of channels and transporters – a focus on cystic fibrosis

Figures & data

Figure 1. Imbalance of CFTR and ENaC in cystic fibrosis. In wt cells, CFTR is active at the PM where it secretes Cl⁻ and regulates ENaC-mediated Na⁺ absorption. In CF cells, there is no functional CFTR leading to an increased Na⁺ absorption due to ENaC hyperactivity. These changes result in increased water uptake from the extracellular medium (resulting in the CF-characteristic viscous mucus).

Figure 2. Rab proteins as regulators of CFTR and ENaC membrane trafficking CFTR (blue cartoon) and ENaC (red cartoon) are endocytosed from the PM in clathrin-coated vesicles. Several members of the RabGTPase family have been shown to modulate the trafficking of these proteins. Rab5 promotes their endocytosis of CFTR. Exit of CFTR from early endosomes is mediated by Rab7 which increases CFTR degradation mediated by delivery to late endosomes and lysosomes. Rab9 is involved in CFTR trafficking from late endosomes to the TGN. Rab11 mediates CFTR and ENaC trafficking from recycling endosomes to the PM. Rab3 and Rab27 have also been implicated in CFTR and ENaC trafficking.