title: γ-Secretase-mediated growth hormone receptor proteolysis: mapping of the intramembranous cleavage site.
abstract: GH receptor (GHR) undergoes regulated proteolysis by both metalloprotease (α-secretase) and γ-secretase activities. α-Secretase activity regulates GHR availability and sensitivity and generates circulating GH binding protein. The function of γ-secretase cleavage is yet uncertain. We investigated GHR determinants that affect inducible sequential α- and γ-secretase cleavage and thus remnant and stub generation, respectively. Purification and N-terminal sequencing of the stub revealed that γ-secretase cleavage occurs at an ε-site in GHR's transmembrane domain four residues from the intracellular domain. Mutagenesis revealed that deletion of the proximal two transmembrane residues prevented both α- and γ-secretase-mediated proteolysis and deletion of four residues around the ε-site precluded surface GHR expression and proteolysis. However, point mutations in and around the ε-site affected neither α- or γ-secretase cleavage. We conclude that both cleavages likely occur at the cell surface and sequentially (α-secretase followed by γ-secretase) and that ε-site cleavage by γ-secretase does not require a consensus sequence.
authors.affiliation: Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35294, United States.
authors.forename: Xiangdong
authors.initials: X
authors.lastname: Wang
authors.forename: Jon W
authors.initials: JW
authors.lastname: Cowan
authors.forename: Mary
authors.initials: M
authors.lastname: Gerhart
authors.forename: Blake R
authors.initials: BR
authors.lastname: Zelickson
authors.forename: Jing
authors.initials: J
authors.lastname: Jiang
authors.forename: Kai
authors.initials: K
authors.lastname: He
authors.forename: Michael S
authors.initials: MS
authors.lastname: Wolfe
authors.forename: Roy A
authors.initials: RA
authors.lastname: Black
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Frank
mesh_terms: D000595:Amino Acid Sequence; D053829:Amyloid Precursor Protein Secretases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D004252:DNA Mutational Analysis; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D011817:Rabbits; D051381:Rats; D011986:Receptors, Somatotropin / Q000235:genetics / Q000378:metabolism*
chemical_list: D011986:Receptors, Somatotropin; D053829:Amyloid Precursor Protein Secretases