Versatility and differential roles of cysteine residues in human prostacyclin receptor structure and function.
Prostacyclin plays important roles in vascular homeostasis, promoting vasodilatation and inhibiting platelet thrombus formation. Previous studies have shown that three of six cytoplasmic cysteines, particularly those within the C-terminal tail, serve as important lipidation sites and are differentially conjugated to palmitoyl and isoprenyl groups (Miggin, S. M., Lawler, O. A., and Kinsella, B. T. (2003) J. Biol. Chem. 278, 6947-6958). Here we report distinctive roles for extracellular- and transmembrane-located cysteine residues in human prostacyclin receptor structure-function. Within the extracellular domain, all cysteines (4 of 4) appear to be involved in disulfide bonding interactions (i.e. a highly conserved Cys-92-Cys-170 bond and a putative non-conserved Cys-5-Cys-165 bond), and within the transmembrane (TM) region there are several cysteines (3 of 8) that maintain critical hydrogen bonding interactions (Cys-118 (TMIII), Cys-251 (TMVI), and Cys-202 (TMV)). This study highlights the necessity of sulfhydryl (SH) groups in maintaining the structural integrity of the human prostacyclin receptor, as 7 of 12 extracellular and transmembrane cysteines studied were found to be differentially indispensable for receptor binding, activation, and/or trafficking. Moreover, these results also demonstrate the versatility and reactivity of these cysteine residues within different receptor environments, that is, extracellular (disulfide bonds), transmembrane (H-bonds), and cytoplasmic (lipid conjugation).
Stitham
Jeremiah
J
Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Gleim
Scott R
SR
Douville
Karen
K
Arehart
Eric
E
Hwa
John
J
D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D003545:Cysteine / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D044006:Receptors, Epoprostenol / Q000737:chemistry*; D013329:Structure-Activity Relationship
D044006:Receptors, Epoprostenol; D003545:Cysteine