title: ER stress disrupts Ca2+-signaling complexes and Ca2+ regulation in secretory and muscle cells from PERK-knockout mice.
abstract: Disruption of protein synthesis and folding results in ER stress, which is associated with the pathophysiology of diverse diseases affecting secretory and muscle cells. Cells are protected against ER stress by activation of the unfolded protein response (UPR) that is regulated by the protein kinase PERK, which phosphorylates the translation initiation factor 2 eIF2alpha to attenuate protein synthesis. PERK-/- cells are unable to modulate ER protein load and experience high levels of ER stress. In addition to its role in protein synthesis, the ER also orchestrates many signaling events essential for cell survival, prominent among which is Ca2+ signaling. It is not known, however, whether there is a relationship between ER stress and the function of the Ca2+-signaling pathway in muscle and non-muscle cells. To directly address this question we characterized Ca2+ signaling in the secretory pancreatic and parotid acinar cells and in urinary bladder smooth muscle (UBSM) cells obtained from PERK-/- and wild-type mice. Deletion of PERK that results in high levels of ER stress, and distention and fragmentation of the ER slowed the rate of agonist-mediated Ca2+ release from the ER and reduced Ca2+-induced Ca2+ release, although IP3 production, localization of the IP3 receptors, IP3-mediated Ca2+ release, Ca(v)1.2 current and RyRs activity remained unaltered. On the other hand, ER stress disrupted the integrity of the Ca2+-signaling complexes in both secretory and UBSM cells, as revealed by markedly reduced co-immunoprecipitation of plasma membrane- and ER-resident Ca2+-signaling proteins. These findings establish a relationship between the unfolding protein response, ER stress and Ca2+ signaling and highlight the importance of communication within the terminal ER-plasma membrane microdomain for propagation of the Ca2+ signal from the plasma membrane into the cell.
authors.affiliation: Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
authors.forename: Guojin
authors.initials: G
authors.lastname: Huang
authors.forename: Jian
authors.initials: J
authors.lastname: Yao
authors.forename: Weizhong
authors.initials: W
authors.lastname: Zeng
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Mizuno
authors.forename: Kristine E
authors.initials: KE
authors.lastname: Kamm
authors.forename: James T
authors.initials: JT
authors.lastname: Stull
authors.forename: Heather P
authors.initials: HP
authors.lastname: Harding
authors.forename: David
authors.initials: D
authors.lastname: Ron
authors.forename: Shmuel
authors.initials: S
authors.lastname: Muallem
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism; D010179:Pancreas / Q000166:cytology; D001743:Urinary Bladder / Q000033:anatomy & histology; D019892:eIF-2 Kinase / Q000235:genetics / Q000378:metabolism*
chemical_list: D002118:Calcium; D015544:Inositol 1,4,5-Trisphosphate; D019892:eIF-2 Kinase