title: Cytoplasmic domain of P-selectin glycoprotein ligand-1 facilitates dimerization and export from the endoplasmic reticulum.
abstract: P-selectin glycoprotein ligand-1 (PSGL-1) is a homodimeric transmembrane mucin on leukocytes. During inflammation, reversible interactions of PSGL-1 with selectins mediate leukocyte rolling on vascular surfaces. The transmembrane domain of PSGL-1 is required for dimerization, and the cytoplasmic domain propagates signals that activate β(2) integrins to slow rolling on integrin ligands. Leukocytes from knock-in "ΔCD" mice express a truncated PSGL-1 that lacks the cytoplasmic domain. Unexpectedly, they have 10-fold less PSGL-1 on their surfaces than WT leukocytes. Using glycosidases, proteases, Western blotting, confocal microscopy, cell-surface cross-linking, FRET, and pulse-chase metabolic labeling, we demonstrate that deleting the cytoplasmic domain impaired dimerization and delayed export of PSGL-1 from the endoplasmic reticulum (ER), markedly increasing a monomeric precursor in the ER and decreasing mature PSGL-1 on the cell surface. A monomeric full-length PSGL-1 made by substituting the transmembrane domain with that of CD43 exited the ER normally, revealing that dimerization was not required for ER export. Thus, the transmembrane and cytoplasmic domains cooperate to promote dimerization of PSGL-1. Furthermore, the cytoplasmic domain provides a key signal to export precursors of PSGL-1 from the ER to the Golgi apparatus en route to the cell surface.
authors.affiliation: Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Miner
authors.forename: Bojing
authors.initials: B
authors.lastname: Shao
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.forename: Gurunadh R
authors.initials: GR
authors.lastname: Chichili
authors.forename: Zhenghui
authors.initials: Z
authors.lastname: Liu
authors.forename: Arkadiusz G
authors.initials: AG
authors.lastname: Klopocki
authors.forename: Tadayuki
authors.initials: T
authors.lastname: Yago
authors.forename: J Michael
authors.initials: JM
authors.lastname: McDaniel
authors.forename: William
authors.initials: W
authors.lastname: Rodgers
authors.forename: Lijun
authors.initials: L
authors.lastname: Xia
authors.forename: Rodger P
authors.initials: RP
authors.lastname: McEver
mesh_terms: D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000235:genetics; D006224:Cricetinae; D003412:Cricetulus; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D006056:Golgi Apparatus / Q000235:genetics / Q000378:metabolism; D007249:Inflammation / Q000235:genetics / Q000378:metabolism; D036904:Leukocyte Rolling / Q000502:physiology*; D007962:Leukocytes / Q000166:cytology / Q000378:metabolism*; D051917:Leukosialin / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D055503:Protein Multimerization / Q000502:physiology*; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000502:physiology
chemical_list: D051917:Leukosialin; D008562:Membrane Glycoproteins; C084882:P-selectin ligand protein; C497863:Spn protein, mouse