Ins and outs of the ABCG2 multidrug transporter: An update on in vitro functional assays

Hegedüs, Csilla; Szakács, Gergely; Homolya, László; Orbán, Tamás I.; Telbisz, Ágnes; Jani, Márton; Sarkadi, Balázs

doi:10.1016/j.addr.2008.09.007

Cited by 54 publications

(46 citation statements)

References 108 publications

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“…A key advantage of the insect cell overexpression system is that isolated membrane preparations contain a much higher level of ABCG2 than membranes isolated from mammalian overexpression systems (Ozvegy et al, 2001), thus providing an efficient tool for examining the modulation of ABCG2 ATPase or transport activity (Hegedus et al, 2009). Based on our present observations, we suggest that to obtain maximum activation with ABCG2 substrates, cholesterolloaded insect membranes should be used in the presence of bile acids.…”

Section: Discussionmentioning

confidence: 69%

Regulation of the Function of the Human ABCG2 Multidrug Transporter by Cholesterol and Bile Acids: Effects of Mutations in Potential Substrate and Steroid Binding Sites

et al. 2014

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ABCG2 (ATP-binding cassette, subfamily G, member 2) is a plasma membrane glycoprotein that actively extrudes xenobiotics and endobiotics from the cells and causes multidrug resistance in cancer. In the liver, ABCG2 is expressed in the canalicular membrane of hepatocytes and excretes its substrates into the bile. ABCG2 is known to require high membrane cholesterol content for maximal activity, and by examining purified ABCG2 reconstituted in proteoliposomes we have recently shown that cholesterol is an essential activator, while bile acids significantly modify the activity of this protein. In the present work, by using isolated insect cell membrane preparations expressing human ABCG2 and its mutant variants, we have analyzed whether certain regions in this protein are involved in sterol recognition. We found that replacing ABCG2-R482 with large amino acids does not affect cholesterol dependence, but changes to small amino acids cause altered cholesterol sensitivity. When leucines in the potential steroid-binding element (SBE, aa 555-558) of ABCG2 were replaced by alanines, cholesterol dependence of ABCG2 activity was strongly reduced, although the L558A mutant variant when purified and reconstituted still required cholesterol for full activity. Regarding the effect of bile acids in isolated membranes, we found that these compounds decreased ABCG2-ATPase in the absence of drug substrates, which did not significantly affect substrate-stimulated ATPase activity. These ABCG2 mutant variants also altered bile acid sensitivity, although cholic acid and glycocholate were not transported by the protein. We suggest that the aforementioned two regions in ABCG2 are important for sterol sensing and may represent potential targets for pharmacologic modulation of ABCG2 function.

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Section: Discussionmentioning

confidence: 69%

Regulation of the Function of the Human ABCG2 Multidrug Transporter by Cholesterol and Bile Acids: Effects of Mutations in Potential Substrate and Steroid Binding Sites

et al. 2014

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“…Cholesterol levels have been shown to be involved in the regulation of various membrane proteins, including ABCG2 [11]. Membrane cholesterol was also found to modulate ABCG2 activity in a selective and reversible manner [12].…”

Section: Introductionmentioning

confidence: 99%

Cholesterol reduces the sensitivity to platinum-based chemotherapy via upregulating ABCG2 in lung adenocarcinoma

Tang

et al. 2015

Biochemical and Biophysical Research Communications

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“…However, findings from in vitro studies are not as clear-cut and have not ruled out a role for Abcg2 in bile acid transport. A potential explanation is that ABCG2 activity is influenced by a combination of the membrane microenvironment and the inherent properties of ABCG2 (Hegedus et al, 2009b). For example, recent studies have demonstrated that the activity of some ABC transporters is regulated by membrane cholesterol levels (Paulusma et al, 2009).…”

Section: Liver Transporters In Health and Diseasementioning

confidence: 99%

The Role of Transporters in Toxicity and Disease

2014

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The significance of transporters in the disposition, metabolism, and elimination of drugs is well recognized. One gap in our knowledge is a comprehensive understanding of how drug transporters change functionality (their amount and activity) in response to disease and how disease and its inevitable pathology change transporter expression. In this issue of Drug Metabolism and Disposition a series of review and primary research articles are presented to highlight the importance of transporters in toxicity and disease. Because of the central role of the liver in drug metabolism, many of the articles in this theme issue focus on transporters in the liver and how pathology or alterations in physiology affects transporter expression. The contributing authors have also considered the role of transporters in drug interactions as well as drug-induced liver injury. Noninvasive approaches to assessing transporter function in vivo are also described. Several articles highlight important issues in oncology where toxicity must be balanced against efficacy. In total, this theme issue will provide a stepping-stone to future studies that will establish a more comprehensive understanding of transporters in disease.

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Ins and outs of the ABCG2 multidrug transporter: An update on in vitro functional assays

Cited by 54 publications

References 108 publications

Regulation of the Function of the Human ABCG2 Multidrug Transporter by Cholesterol and Bile Acids: Effects of Mutations in Potential Substrate and Steroid Binding Sites

Regulation of the Function of the Human ABCG2 Multidrug Transporter by Cholesterol and Bile Acids: Effects of Mutations in Potential Substrate and Steroid Binding Sites

Cholesterol reduces the sensitivity to platinum-based chemotherapy via upregulating ABCG2 in lung adenocarcinoma

The Role of Transporters in Toxicity and Disease

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