title: RGS4 and RGS5 are in vivo substrates of the N-end rule pathway.
abstract: The ATE1-encoded Arg-transferase mediates conjugation of Arg to N-terminal Asp, Glu, and Cys of certain eukaryotic proteins, yielding N-terminal Arg that can act as a degradation signal for the ubiquitin-dependent N-end rule pathway. We have previously shown that mouse ATE1-/- embryos die with defects in heart development and angiogenesis. Here, we report that the ATE1 Arg-transferase mediates the in vivo degradation of RGS4 and RGS5, which are negative regulators of specific G proteins whose functions include cardiac growth and angiogenesis. The proteolysis of these regulators of G protein signaling (RGS) proteins was perturbed either by hypoxia or in cells lacking ubiquitin ligases UBR1 and/or UBR2. Mutant RGS proteins in which the conserved Cys-2 residue could not become N-terminal were long-lived in vivo. We propose a model in which the sequential modifications of RGS4, RGS5, and RGS16 (N-terminal exposure of their Cys-2, its oxidation, and subsequent arginylation) act as a licensing mechanism in response to extracellular and intracellular signals before the targeting for proteolysis by UBR1 and UBR2. We also show that ATE1-/- embryos are impaired in the activation of extracellular signal-regulated kinase mitogen-activated protein kinases and in the expression of G protein-induced downstream effectors such as Jun, cyclin D1, and beta-myosin heavy chain. These results establish RGS4 and RGS5 as in vivo substrates of the mammalian N-end rule pathway and also suggest that the O2-ATE1-UBR1/UBR2 proteolytic circuit plays a role in RGS-regulated G protein signaling in the cardiovascular system.
authors.affiliation: Center for Pharmacogenetics and Department of Pharmaceutical Sciences, University of Pittsburgh, 3501 Terrace Street, Pittsburgh, PA 15261, USA.
authors.forename: Min Jae
authors.initials: MJ
authors.lastname: Lee
authors.forename: Takafumi
authors.initials: T
authors.lastname: Tasaki
authors.forename: Kayoko
authors.initials: K
authors.lastname: Moroi
authors.forename: Jee Young
authors.initials: JY
authors.lastname: An
authors.forename: Sadao
authors.initials: S
authors.lastname: Kimura
authors.forename: Ilia V
authors.initials: IV
authors.lastname: Davydov
authors.forename: Yong Tae
authors.initials: YT
authors.lastname: Kwon
mesh_terms: D019881:Aminoacyltransferases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D003545:Cysteine / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D020710:RGS Proteins / Q000235:genetics / Q000378:metabolism*; D015290:Second Messenger Systems / Q000502:physiology*; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: D020710:RGS Proteins; C105346:Rgs5 protein, mouse; D025801:Ubiquitin; C098799:RGS4 protein; D019881:Aminoacyltransferases; D044767:Ubiquitin-Protein Ligases; C019727:arginyltransferase; D019204:GTP-Binding Proteins; D003545:Cysteine