AUTHOR=Bartos Zsuzsa , Homolya László 

TITLE=Identification of Specific Trafficking Defects of Naturally Occurring Variants of the Human ABCG2 Transporter

JOURNAL=Frontiers in Cell and Developmental Biology

VOLUME=Volume 9 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/cell-and-developmental-biology/articles/10.3389/fcell.2021.615729

DOI=10.3389/fcell.2021.615729

ISSN=2296-634X

ABSTRACT=Proper targeting of the urate and xenobiotic transporter ABCG2 to the plasma membrane is essential for its normal function. The naturally occurring Q141K and M71V polymorphisms in ABCG2, associated with gout and hyperuricemia, affect the cellular routing of the transporter, rather than its transport function. The cellular localization of ABCG2 variants was formerly studied by immunolabeling, which provides information only on the steady state distribution of the protein, leaving the dynamics of its cellular routing unexplored. In the present study, we assessed in detail the trafficking of the wild type, M71V-, and Q141K-ABCG2 variants from the endoplasmic reticulum to the cell surface using a dynamic approach, the so-called RUSH (Retention Using Selective Hooks) system. This method also allowed us to study the kinetics of glycosylation of these variants. We found that the fraction of Q141K- and M71V-ABCG2 that passes the endoplasmic reticulum quality control system is only partially targeted to the plasma membrane, a subfraction is immobile and retained in the endoplasmic reticulum. Surprisingly, the transit of these variants through the Golgi apparatus (either the appearance or the exit) was unaffected; however, their plasma membrane delivery beyond the Golgi was delayed. In addition to identifying the specific defects in the trafficking of these ABCG2 variants, our study provides a novel experimental tool for studying the effect of drugs that potentially promote the cell surface delivery of mutant or polymorphic ABCG2 variants with impaired trafficking.