Poster abstracts

Poster number 7 submitted by Wei Liu

Structural basis for ligand-independent dimerization and ligand-induced activation of human prolactin receptor

Wei Liu (Ohio State Biochemistry Program), Timothy J. Gordon (Ohio State Biochemistry Program), Charles L. Brooks (Department of Veterinary Biosciences)

Abstract:
The reports of ligand-independent dimerization of Human Prolactin Receptor (hPRLr) have challenged the classic model of hPRLr activation. The structural elements in hPRLr that mediate its ligand-independent dimerization have not been determined. A new mechanism for hPRLr activation has yet to be described. We have determined a role of disulfide linkage in the ligand-independent dimerization of hPRLr by western blotting on non-reducing SDS-PAGE. This ligand-independent dimeric form of hPRLr was not eliminated by the removal of both C184 and C225 residues, the two non-paired cystein residues outside the intracellular domain (ICD), indicating the role of cystein residues in the ICD. hPRLr mutants with V5 tag or Poly-His tag were also constructed and will be used to determine the role of non-covalent interactions in the transmembrane domain (TMD) in the ligand-independent dimerization. In addition, we have generated hPRLr mutants with one to four alanines inserted between the TMD and the ICD. Constitutive activation of hPRLr was detected only in the mutant with one alanine insertion, although all of the four showed ligand-induced activation. These results provide useful insight on the mechanisms of ligand-independent dimerization and ligand-induced activation of hPRLr.

References:
Brown RJ, et al. Nat Struct Mol Biol 12: 814-821 (2005)
Constantinescu SN, et al. PNAS 98: 4379-4384 (2001)
Gadd SL, Clevenger CV. Mol Endocrinol 20: 2734-2746 (2006)
Quazi AM, et al. Mol Endocrinol 20: 1912-1923 (2006)
Yang N, et al. Mol Endocrinol 21: 1642-1655 (2007)

Keywords: prolactin receptor, dimerization, phosphorylation