Structure and Function Studies of ABCG1

• Author / Creator

  Li, Ge

• ATP-binding cassette transporter G1 (ABCG1) mediates sterol efflux onto lipidated lipoproteins and plays an important role in macrophage cholesterol homeostasis. In this project, we investigated how ABCG1 works as a functional transporter to mediate sterol translocation. First, we found a conserved sequence present in the five ABCG transporter subfamily members. The conserved sequence locates between the nucleotide binding domain and the transmembrane domain and contains five amino acid residues from Asn at position 316 to Phe at position 320 in ABCG1 (NPADF). Detailed mutagenesis study revealed that Asn316 and Phe320 in the conserved sequence played an important role in the regulation of ABCG1 function. We further demonstrated that mutations N316D, N316Q and F320I led to retention of the protein in the endoplasmic reticulum (ER). Thus, the two highly conserved amino acid residues, Asn and Phe, may regulate ABCG1 trafficking, thereby affecting ABCG1-mediated cholesterol efflux. Second, we found a Stat3 binding site (YXXQ) located in the N-terminal cytoplasmic region of ABCG1. Replacement of Tyr at position 157 with Ala essentially eliminated ABCG1-mediated efflux of cholesterol and 7-ketocholesterol. On the other hand, substitution of Gln at position 160 with Ala affected the substrate specificity of ABCG1, reducing 7-ketocholesterol efflux with no significant effect on cholesterol efflux. In summary, we identified residues in the N-terminal cytoplasmic region of ABCG1 important for ABCG1 trafficking, function and substrate specificity.

• Subjects / Keywords

  • ABCG1

• Graduation date

  Fall 2013

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3FQ9QD70

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.