Int J Biochem Mol Biol 2011;2(1):1-7
Original Article
Biochemistry, molecular biology, and pharmacology of fatty acid synthase, an emerging
therapeutic target and diagnosis/prognosis marker
Peng Duan, Jinwei Wu, Guofeng You
Department of Pharmaceutics, Rutgers, the State University of New Jersey, and Department of Pharmacology, UMDNJ-Robert Wood Johnson
Medical School, Piscataway, NJ 08854, USA.
Received September 4, 2010; accepted September 18, 2010; Epub September 20, 2010; published February 15, 2011
Abstract: Human organic anion transporter hOAT1 plays a critical role in the body disposition of environmental toxins and clinically important
drugs including anti-HIV therapeutics, anti-tumor drugs, antibiotics, anti-hypertensives, and anti-inflammatories. hOAT1 has two GXXXG motifs
in its transmembrane domains 2 and 5, a motif linked to the protein processing and oligomerization of other proteins. In the current study, we
substituted glycine of these GXXXG motifs with alanine and evaluated the effect of such mutations on the expression and function of hOAT1.
Mutations of GXXXG motif in the transmembrane domain 2 resulted in mutants G144A and G148A, both of which had no transport activity due to
complete loss in the surface and total cell expression of the transporter protein. Treatment of G144A- and G148A-expressing cells with
proteasomal inhibitor resulted in the recovery of ER-resident immature form of hOAT1, but not its surface-resident mature form, whereas
treatment of these cells with lysosomal inhibitor had no effect on the expression of the mutant transporters. Mutations of GXXXG motif in the
transmembrane domain 5 resulted in mutants G223A and G227A, among which only G227 had dramatic reduction of transport activity due to
dramatic loss in the surface and total cell expression of the transporter. The reduction in the surface expression of G227 was consistent with
the decrease in maximum transport velocity Vmax. Treatment of G227A-expressing cells with proteasomal inhibitor or lysosomal inhibitor
resulted in partial recovery of both the immature form and the mature form of hOAT1 in the total cell extracts. However, such partial recovery of
the mature form in total cell extracts did not lead to the partial recovery of surface expression and function of the transporter. Our data suggest
that the GXXXG motifs in transmembrane domains 2 and 5 play critical roles in the stability of hOAT1. (IJBMB1009001).
Keywords: GXXXG motif, organic anion transporter, drug transport
Full Text PDF
Address all correspondence to:
Guofeng You, PhD
Dept. of Pharmaceutics,
Rutgers, the State University of New Jersey,
160 Frelinghuysen Road, Piscataway, NJ 08854, USA
Tel: 732-445-3831 x 218;
Email: gyou@rci.rutgers.edu
Original Article
Biochemistry, molecular biology, and pharmacology of fatty acid synthase, an emerging
therapeutic target and diagnosis/prognosis marker
Peng Duan, Jinwei Wu, Guofeng You
Department of Pharmaceutics, Rutgers, the State University of New Jersey, and Department of Pharmacology, UMDNJ-Robert Wood Johnson
Medical School, Piscataway, NJ 08854, USA.
Received September 4, 2010; accepted September 18, 2010; Epub September 20, 2010; published February 15, 2011
Abstract: Human organic anion transporter hOAT1 plays a critical role in the body disposition of environmental toxins and clinically important
drugs including anti-HIV therapeutics, anti-tumor drugs, antibiotics, anti-hypertensives, and anti-inflammatories. hOAT1 has two GXXXG motifs
in its transmembrane domains 2 and 5, a motif linked to the protein processing and oligomerization of other proteins. In the current study, we
substituted glycine of these GXXXG motifs with alanine and evaluated the effect of such mutations on the expression and function of hOAT1.
Mutations of GXXXG motif in the transmembrane domain 2 resulted in mutants G144A and G148A, both of which had no transport activity due to
complete loss in the surface and total cell expression of the transporter protein. Treatment of G144A- and G148A-expressing cells with
proteasomal inhibitor resulted in the recovery of ER-resident immature form of hOAT1, but not its surface-resident mature form, whereas
treatment of these cells with lysosomal inhibitor had no effect on the expression of the mutant transporters. Mutations of GXXXG motif in the
transmembrane domain 5 resulted in mutants G223A and G227A, among which only G227 had dramatic reduction of transport activity due to
dramatic loss in the surface and total cell expression of the transporter. The reduction in the surface expression of G227 was consistent with
the decrease in maximum transport velocity Vmax. Treatment of G227A-expressing cells with proteasomal inhibitor or lysosomal inhibitor
resulted in partial recovery of both the immature form and the mature form of hOAT1 in the total cell extracts. However, such partial recovery of
the mature form in total cell extracts did not lead to the partial recovery of surface expression and function of the transporter. Our data suggest
that the GXXXG motifs in transmembrane domains 2 and 5 play critical roles in the stability of hOAT1. (IJBMB1009001).
Keywords: GXXXG motif, organic anion transporter, drug transport
Full Text PDF
Address all correspondence to:
Guofeng You, PhD
Dept. of Pharmaceutics,
Rutgers, the State University of New Jersey,
160 Frelinghuysen Road, Piscataway, NJ 08854, USA
Tel: 732-445-3831 x 218;
Email: gyou@rci.rutgers.edu
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