Folding correction of ABC‐transporter ABCB1 by pharmacological chaperones: a mechanistic concept

Abstract

Point mutations of ATP‐binding cassette (ABC) proteins are a common cause of human diseases. Available crystal structures indicate a similarity in the architecture of several members of this protein family. Their molecular architecture makes these proteins vulnerable to mutation, when critical structural elements are affected. The latter preferentially involve the two transmembrane domain (TMD)/nucleotide‐binding domain (NBD) interfaces (transmission interfaces), formation of which requires engagement of coupling helices of intracellular loops with NBDs. Both, formation of the active sites and engagement of the coupling helices, are contingent on correct positioning of ICLs 2 and 4 and thus an important prerequisite for proper folding. Here, we show that active site compounds are capable of rescuing P‐glycoprotein (P‐gp) mutants ∆Y490 and ∆Y1133 in a concentration‐dependent manner. These trafficking deficient mutations are located at the transmission interface in pseudosymmetric position to each other. In addition, the ability of propafenone analogs to correct folding correlates with their ability to inhibit transport of model substrates. This finding indicates that folding correction and transport inhibition by propafenone analogs are brought about by binding to the active sites. Furthermore, this study demonstrates an asymmetry in folding correction with cis‐flupentixol, which reflects the asymmetric binding properties of this modulator to P‐gp. Our results suggest a mechanistic model for corrector action in a model ABC transporter based on insights into the molecular architecture of these transporters.

Molecular Mechanism of Taurocholate Transport by the Bile Salt Export Pump, an ABC Transporter Associated with Intrahepatic Cholestasis

“…In full transporters (commonly appreciated to have arisen from half transporters by gene duplication) (Chen et al, 1986), the two halves have diverged in the course of evolution, but nevertheless have retained similarity. Our group previously demonstrated that the paradigmatic ABCB transporter P-gp (ABCB1) can bind substrates such as rhodamine 123, verapamil, vinblastine, and propafenones in dual pseudosymmetric mode (Parveen et al, 2011;Dönmez Cakil et al, 2014;Spork et al, 2017). As P-gp has two canonical NBSs, the possibility exists that substrate-binding modes and NBSs function in dedicated manner.…”

The noncanonical nucleotide binding site 1 of the bile salt export pump is optimized for proper function of the transporter

“…Available high-resolution structures and biochemical evidence indicate that alpha helices of the two TMDs interact to form substrate translocation conduits for the transport of cargo molecules (Dawson & Locher, 2006;Dönmez Cakil et al, 2014;Nosol et al, 2020;Parveen et al, 2011;Spork et al, 2017). Two nucleotide binding sites (NBSs) are formed at the interface of the NBDs.…”

“…A functional ATP‐binding cassette (ABC) transporter contains at least four domains: two are spanning the membrane and are therefore called transmembrane domains (TMDs), while the other two are known as the nucleotide‐binding domains (NBDs). Available high‐resolution structures and biochemical evidence indicate that alpha helices of the two TMDs interact to form substrate translocation conduits for the transport of cargo molecules (Dawson & Locher, 2006; Dönmez Cakil et al, 2014; Nosol et al, 2020; Parveen et al, 2011; Spork et al, 2017). Two nucleotide binding sites (NBSs) are formed at the interface of the NBDs.…”