RGSZ1 and Ret RGS: Two of Several Splice Variants from the Gene RGS20

We have isolated an RGS-GAIP interacting protein that links RGS proteins to protein degradation. GIPN (GAIP interacting protein N terminus) is a 38-kDa protein with an N-terminal leucine-rich region, a central RING finger-like domain, and a putative C-terminal transmembrane domain. GIPN binds exclusively to RGS proteins of subfamily A, RGS-GAIP, RGSZ1, and RGSZ2. The N-terminal leucinerich region of GIPN interacts with the cysteine-rich motif of RGS-GAIP. GIPN mRNA is ubiquitously expressed, and GIPN is found on the plasma membrane of transfected HEK293 cells. Endogenous GIPN is concentrated along the basolateral plasma membrane of proximal and distal tubules in rat kidney, where many G proteincoupled receptors and some G proteins are also located. Two immunoreactive species are found in rat kidney, a 38-kDa cytosolic form and an Ϸ94-kDa membrane form. GIPN shows Zn 2؉ -and E1͞E2-dependent autoubiquitination in vitro, suggesting that it has E3 ubiquitin ligase activity. Overexpression of GIPN stimulates proteasome-dependent reduction of endogenous G␣i3 in HEK293 cells and reduces the half-life of overexpressed G␣i3-YFP. Thus, our findings suggest that GIPN is involved in the degradation of G␣i3 subunits via the proteasome pathway. RGS-GAIP functions as a bifunctional adaptor that binds to G␣ subunits through its RGS domain and to GIPN through its cysteine string motif.

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“…3A). Interestingly, GIPN did not interact with RET-RGS1, an alternatively spliced form of RGSZ1 with a 156-aa, N-terminal extension (30,31).…”

Section: Gipn Interacts With Subfamily a Rgs Proteinsmentioning

confidence: 94%

Promotion of Gαi3 subunit down-regulation by GIPN, a putative E3 ubiquitin ligase that interacts with RGS-GAIP

Vries

Meerloo

Farquhar

2003

Proc. Natl. Acad. Sci. U.S.A.

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“…Neural RGS-Rz proteins isolated from synaptosomal membranes display different sizes (Garzón et al, 2004(Garzón et al, , 2005a and while this may be due to splicing of the RGSZ1 gene (Barker et al, 2001), RGSZ2 does not appear to be subjected to such events (Mao et al, 2004). Thus, the different isoforms of these RGS-Rz proteins are more likely generated by post-translational modifications such as glycosylation.…”

Section: Introductionmentioning

confidence: 99%

Sumoylated RGS-Rz Proteins Act as Scaffolds for Mu-Opioid Receptors and G-Protein Complexes in Mouse Brain

Rodríguez-Muñoz

Bermúdez

Sánchez‐Blázquez

et al. 2006

Neuropsychopharmacol

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The RGSZ1 and RGSZ2 proteins, members of the RGS-Rz subfamily of GTPase-activating proteins (GAP), are involved in Mu-opioid receptor desensitization. The expression of these proteins, as well as of their main target the Gz protein, is virtually restricted to the nervous tissue. In synaptosomal membranes, these Rz proteins undergo post-translational modifications such as glycosylation and phosphorylation, and they may covalently attach to small ubiquitin-like modifier (SUMO) proteins. While RGSZ1 exists in conjugated and non-conjugated forms, RGSZ2 is mostly conjugated to SUMO-1, SUMO-2 and SUMO-3 proteins. These sumoylated forms of the GAPs readily associated with Mu-opioid receptors but they associated only poorly with Delta receptors. Furthermore, Gai2 and Gaz subunits co-precipitated with the sumoylated forms of RGSZ1/Z2 proteins, but to a lesser extent with the Ser phosphorylated SUMO-free form of RGSZ1. Upon Mu-opioid receptor activation, there is a strong increase in the association of Ga proteins with RGSZ2 proteins that persists for intervals longer than 24 h. This effect probably accounts for their role in Mu-opioid receptor desensitization. Only a moderate increase was observed with RGSZ1, the non-sumoylated form of which probably acts as an efficient GAP for these Ga subunits. Therefore, sumoylation regulates the biological activity of RGS-Rz proteins and it is likely that it serves to switch their behavior, from that of a GAP for activated Ga subunits to that of a scaffold protein for specific signaling proteins.

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“…By contrast, the RGSZ-like and RGS4-like (R4/B) subfamilies are made up of smaller proteins containing a RGS-box domain flanked by short aminoterminal and carboxyl-terminal extensions. These two families are distinguished by the presence of a polycysteine domain in the amino terminus of the RGSZ-like members (7,8) that is believed to be reversibly palmitoylated (9). Members of the mammalian R4/B subfamily include RGS1, RGS2, RGS3, RGS4, RGS5, RGS8, RGS16, RGS18, and RGS21.…”

mentioning

confidence: 99%

Unique Hydrophobic Extension of the RGS2 Amphipathic Helix Domain Imparts Increased Plasma Membrane Binding and Function Relative to Other RGS R4/B Subfamily Members

et al. 2007

Journal of Biological Chemistry

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RGS2 and RGS5 are inhibitors of G-protein signaling belonging to the R4/B subfamily of RGS proteins. We here show that RGS2 is a much more potent attenuator of M1 muscarinic receptor signaling than RGS5. We hypothesize that this difference is mediated by variation in their ability to constitutively associate with the plasma membrane (PM). Compared with full-length RGS2, the RGS-box domains of RGS2 and RGS5 both show reduced PM association and activity. Prenylation of both RGSbox domains increases activity to RGS2 levels, demonstrating that lipid bilayer targeting increases RGS domain function. Amino-terminal domain swaps confirm that key determinants of localization and function are found within this important regulatory domain. An RGS2 amphipathic helix domain mutant deficient for phospholipid binding (L45D) shows reduced PM association and activity despite normal binding to the M1 muscarinic receptor third intracellular loop and activated G␣ q . Replacement of a unique dileucine motif adjacent to the RGS2 helix with corresponding RGS5 residues disrupts both PM localization and function. These data suggest that RGS2 contains a hydrophobic extension of its helical domain that imparts high efficiency binding to the inner leaflet of the lipid bilayer. In support of this model, disruption of membrane phospholipid composition with N-ethylmaleimide reduces PM association of RGS2, without affecting localization of the M1 receptor or G␣ q . Together, these data indicate that novel features within the RGS2 amphipathic ␣ helix facilitate constitutive PM targeting and more efficient inhibition of M1 muscarinic receptor signaling than RGS5 and other members of the R4/B subfamily.Heterotrimeric G-protein-coupled receptors mediate cellular responses to a variety of extracellular ligands, including hormones, neurotransmitters, and sensory stimuli. Proper coordination of G-protein-coupled receptor signaling at the cellular and tissue level is required to ensure appropriate physiologic responses to rapidly changing environmental conditions. An important component of G-protein-coupled receptors signal coordination in human cells is the RGS (regulator of G-protein signaling) superfamily of proteins. RGS proteins inhibit G-protein signaling via their activities as GTPase-activating proteins for G-protein ␣ subunits (1-4).The human genome contains 37 RGS proteins (5) characterized by a ϳ120-amino acid domain called the "RGS-box." The RGS protein superfamily can be further subclassified based on the architectural organization and RGS-box function of its members (6). Many subfamilies are made up of larger RGS-boxcontaining proteins that include the RGS7-like, RGS12-like, RhoGEF-containing, and G-protein-coupled receptor kinases. These subfamilies are mainly composed of members with multiple modular signaling domains. By contrast, the RGSZ-like and RGS4-like (R4/B) subfamilies are made up of smaller proteins containing a RGS-box domain flanked by short aminoterminal and carboxyl-terminal extensions. These two families are distinguishe...

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RGSZ1 and Ret RGS: Two of Several Splice Variants from the Gene RGS20

Cited by 33 publications

References 24 publications

Promotion of Gαi3 subunit down-regulation by GIPN, a putative E3 ubiquitin ligase that interacts with RGS-GAIP

Promotion of Gαi3 subunit down-regulation by GIPN, a putative E3 ubiquitin ligase that interacts with RGS-GAIP

Sumoylated RGS-Rz Proteins Act as Scaffolds for Mu-Opioid Receptors and G-Protein Complexes in Mouse Brain

Unique Hydrophobic Extension of the RGS2 Amphipathic Helix Domain Imparts Increased Plasma Membrane Binding and Function Relative to Other RGS R4/B Subfamily Members

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