Int J Biochem Mol Biol 2012;3(3):290-301
Original Article
Human Organic Solute Transporter (hOST): protein interaction and membrane sorting
process
An-Qiang Sun, Libin Zhu, Yuhuan Luo, Shuhua Xu, Jing Lin, Frederick J Suchy
Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, CO 80045; Department of Pediatrics, Mount Sinai School
of Medicine, NY, NY 10029; 3Department of Pediatric Surgery, The Yuying Children’s Hospital of WenZhou Medical College, WenZhou, PR
China.
Received May 24, 2012; Accepted July 2, 2012; Epub September 25, 2012; Published September 30, 2012
Abstract: The human organic solute transporter (hOST) is a heterodimer composed of alpha and beta subunits. Physical association of
hOSTα and β subunits is essential for their polarized basolateral plasma membrane localization and function in the export of bile acids and
steroids. To understand the role of carboxyl- and amino-tails of OSTβ and mechanisms underlying membrane localization of hOST, the effects
of tail deletion of the hOSTβ subunit and biological reagents on membrane distribution and transport function of hOST were investigated in
stably transfected MDCK cells. After deletion of 35 amino acids from the amino-tail of hOSTβ, the efflux transport activity and polarized
membrane distribution of the truncated hOSTβ was abolished. A co-immunoprecipitation study verified that the amino-tail of hOSTβ is
essential for the association with hOSTα subunit. Treatments with cytochalasin D (interrupting actin-filaments), bafilomycin A1 (inhibiting
vacuolar H+-ATPase), brefeldin A (disrupting the Golgi complex), and calphostin C (inhibiting protein kinase C), significantly disrupted the
polarized membrane distribution of hOST and markedly reduced transport activity in stably transfected MDCK cells. In summary, the 35 amino
acid amino-terminal fragment of hOSTβ contains critical information for interaction with the hOSTα subunit and subsequent trafficking to the
plasma membrane. These studies suggest that the membrane sorting process of hOST is mediated by a bafilomycin A1-sensitive vesicular
pathway that is associated with the actin-cytoskeleton network. The membrane localization of hOST is also partially mediated through a
brefeldin A sensitive mechanism, which controls its transit from the ER to Golgi and is regulated by PKC. (IJBMB1205005).
Keywords: Human OST, protein interaction, membrane trafficking, organic anion transporter
Address all correspondence to:
An-Qiang Sun
Department of Pediatrics
University of Colorado Denver School of Medicine
Aurora, CO 80045, USA.
Phone: (303) 724-5925; Fax: (303)-724-3217
E-mail: An-Qiang.Sun@ucdenver.edu
Original Article
Human Organic Solute Transporter (hOST): protein interaction and membrane sorting
process
An-Qiang Sun, Libin Zhu, Yuhuan Luo, Shuhua Xu, Jing Lin, Frederick J Suchy
Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, CO 80045; Department of Pediatrics, Mount Sinai School
of Medicine, NY, NY 10029; 3Department of Pediatric Surgery, The Yuying Children’s Hospital of WenZhou Medical College, WenZhou, PR
China.
Received May 24, 2012; Accepted July 2, 2012; Epub September 25, 2012; Published September 30, 2012
Abstract: The human organic solute transporter (hOST) is a heterodimer composed of alpha and beta subunits. Physical association of
hOSTα and β subunits is essential for their polarized basolateral plasma membrane localization and function in the export of bile acids and
steroids. To understand the role of carboxyl- and amino-tails of OSTβ and mechanisms underlying membrane localization of hOST, the effects
of tail deletion of the hOSTβ subunit and biological reagents on membrane distribution and transport function of hOST were investigated in
stably transfected MDCK cells. After deletion of 35 amino acids from the amino-tail of hOSTβ, the efflux transport activity and polarized
membrane distribution of the truncated hOSTβ was abolished. A co-immunoprecipitation study verified that the amino-tail of hOSTβ is
essential for the association with hOSTα subunit. Treatments with cytochalasin D (interrupting actin-filaments), bafilomycin A1 (inhibiting
vacuolar H+-ATPase), brefeldin A (disrupting the Golgi complex), and calphostin C (inhibiting protein kinase C), significantly disrupted the
polarized membrane distribution of hOST and markedly reduced transport activity in stably transfected MDCK cells. In summary, the 35 amino
acid amino-terminal fragment of hOSTβ contains critical information for interaction with the hOSTα subunit and subsequent trafficking to the
plasma membrane. These studies suggest that the membrane sorting process of hOST is mediated by a bafilomycin A1-sensitive vesicular
pathway that is associated with the actin-cytoskeleton network. The membrane localization of hOST is also partially mediated through a
brefeldin A sensitive mechanism, which controls its transit from the ER to Golgi and is regulated by PKC. (IJBMB1205005).
Keywords: Human OST, protein interaction, membrane trafficking, organic anion transporter
Address all correspondence to:
An-Qiang Sun
Department of Pediatrics
University of Colorado Denver School of Medicine
Aurora, CO 80045, USA.
Phone: (303) 724-5925; Fax: (303)-724-3217
E-mail: An-Qiang.Sun@ucdenver.edu
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